IMMERSED BOUNDARY CONDITIONS METHOD FOR COMPUTATIONAL FLUID DYNAMICS PROBLEMS

This dissertation presents implicit spectrally-accurate algorithms based on the concept of immersed boundary conditions (IBC) for solving a range of computational fluid dynamics (CFD) problems where the physical domains involve boundary irregularities. Both fixed and moving irregularities are considered with particular emphasis placed on the two-dimensional moving boundary problems. The physical model problems considered are comprised of the Laplace operator, the biharmonic operator and the Navier-Stokes equations, and thus cover the most commonly encountered types of operators in CFD analyses. The IBC algorithm uses a fixed and regular computational domain with flow domain immersed inside the computational domain. Boundary conditions along the edges of the time-dependent flow domain enter the algorithm in the form of internal constraints. Spectral spatial discretization for two-dimensional problems is based on Fourier expansions in the stream-wise direction and Chebyshev expansions in the normal-to-the-wall direction. Up to fourth-order implicit temporal discretization methods have been implemented. The IBC algorithm is shown to deliver the theoretically predicted accuracy in both time and space. Construction of the boundary constraints in the IBC algorithm provides degrees of freedom in excess of that required to formulate a closed system of algebraic equations. The ‘classical IBC formulation’ works by retaining number boundary constraints that are just sufficient to form a closed system of equations. The use of additional boundary constraints leads to the ‘over-determined formulation’ of the IBC algorithm. Over- determined systems are explored in order to improve the accuracy o f the IBC method and to expand its applicability to more extreme geometries. Standard direct over-determined solvers based on evaluation of pseudo-inverses of the complete coefficient matrices have been tested on three model problems, namely, the Laplace equation, the biharmonic equation and the Navier-Stokes equations. In all cases tested the over-determined formulations based on standard solvers were found to improve the accuracy and the range o f applicability o f the IBC method. Efficient linear solvers suitable for the spectral implementation of the IBC method have been developed and tested in the context of two-dimensional steady and unsteady Stokes flow in the presence of fixed boundary irregularities. These solvers can work with the classical as well as the over-determined formulations of the method. Significant acceleration of the computations as well as significant reduction of the memory requirements have been accomplished by taking advantage of the structure of the coefficient matrix resulting from the implementation of the IBC algorithm. Performances of the new solvers have been compared with the standard direct solvers and are shown to be of up to two orders of magnitude better. It has been determined that the new methods are by at least an order of magnitude faster than the iterative methods while removing restrictions based on the convergence criteria and thus expanding the severity of the geometries that can be dealt with using the IBC algorithm. The performance of the IBC method combined with the new solvers has been compared with the performance of a method based on the generation of the boundary conforming grids, and is found to be better by at least two orders of magnitude. Application of the new solvers to the unsteady problems also results in performance improvement of up to two orders of magnitude. The specialized solvers applied to the over-determined formulation is shown to be at least two orders of magnitude faster than their standard counterparts while capable of extending the range of applicability of the IBC algorithm by 50%-70% for the Stokes flow problem. The concept of the specialized solvers has been extended to solve two-dimensional moving boundary problems described by the Navier-Stokes equations, where the new solver has been shown to result in a significant acceleration of computations as well as substantial reduction in memory requirements. The conceptual aspects of extending the IBC algorithm for solving three-dimensional problems have been presented using the vorticity-velocity formulation of the three- dimensional Navier-Stokes equations. Test results on the implementation of the IBC algorithm for three-dimensional problems are discussed in the context of heat diffusion IV problems in the presence of fixed as well as moving boundaries. The algorithm is shown to be spectrally-accurate in space and capable of delivering theoretically predicted accuracy in time for the different test problems. Given a potentially large size of the resultant linear algebraic system, various methods that take advantage of the special structure of the coefficient matrix have been explored in search for an efficient solver, including two versions of the specialized direct solver as well as serial and parallel iterative solvers. Both versions of the specialized direct solver have been shown to be more computationally efficient than the other solution methods. Possible applications of the IBC algorithm for analyzing physical problems have also been presented. The advantage of using IBC algorithm is illustrated by considering its application to two physical problems, which are - i) analysis of the effects of distributed roughness on friction factor and ii) analysis of traveling wave instability in wavy channels. These examples clearly show the attractiveness of the IBC algorithm for studying effects of a large array of boundary geometries on the flow field

Performance and area optimization for reliable FPGA-based shifter design

This thesis addresses the problem of implementing reliable FPGA-based shifters. An FPGA-based design requires optimization between performance and resource utilization, and an effective verification methodology to validate design behavior. The FPGA-based implementation of a large shifter design is restricted by an I/O resource bottleneck. The verification of the design behavior presents a further challenge due to the \u27black-box\u27 nature of FPGAs. To tackle these design challenges, we propose a novel approach to implement FPGA-based shifters. The proposed design alleviates the I/O bottleneck while significantly reducing the logic resources required. This is achieved with a minimal increase in the design delay. The design is seamlessly scalable to a multi-FPGA chip setup to improve performance or to implement larger shifters. It is configured using assertion checkers for efficient design verification. The assertion-based design is further optimized to alleviate the performance degradation caused by the assertion checkers

Perfect Capital Mobility, Taxation, Money Illusion, and Devaluations

Are devaluations contractionary? This question has been with us for a long time. The conventional Keynesian economist holds the view that if devaluation is demandexpansionary, then both output and balance-of-payments will improve with devaluation. Experience, however, shows contrary outcomes. For example, Sheehy (1986), who has covered 16 Latin American countries, concluded that devaluation was highly contractionary in these countries. Edwards (1986), on the other hand, has covered 12 less developed countries (LDCs) and found that devaluations are contractionary in the impact period, while in the long-run they all become neutral. Hamarious (1989) has used the data for the periods 1953-73 and 1975-84 and has covered twenty-seven countries and six devaluation episodes to study the effects of devaluations upon prices and the trade balance. He found that in over 80 percent of the cases, devaluation causes a net improvement in the trade balance both in the impact period and in the middle period. The study concluded that the effects of devaluation upon the trade balance last for two to three years. Such results seriously challenge the theoretical results derived by the conventional economist

Evaluation and In Vitro Studies of Folate PEG Biotin and other PEG Agents

Folate is a member of vitamin B family and plays an essential role in cell survival by participating in the biosynthesis of nucleic and amino acids. Receptors folic acid are frequently over expressed on epithelial cancer cells. These receptors are believed to serve as a receptor-mediated transport system of folic acid into cancer cells and cells associated with inflammation. Interesting, most normal cells in the body have lower frequency of these receptors. Based on these attributes, folate based drug delivery, imaging systems, and diagnostic systems are in several stages of development worldwide. In this current project, we have characterized the affinity of the proprietary folate PEG-biotin-fluorescein- (FPBF) conjugate synthesized by Dr. Walter Henne. We have successfully purified and characterized FPBF capture ligand using LC/MS. Further, affinity studies of FPFB towards Streptavidin coated Dynabeads was carried out utilizing fluorescein microscopy. It was demonstrated that the conjugate has site specific interaction toward the Streptavidin coated Dynabeads, a much important characteristic for the effective cancer cell capture. The inexpensive and previously produced folate probe may be substituted for the more costly and cumbersome antibody based ligands, which are typically used for this method of drug delivery system to treat cancer. This method significantly reduces false positive events associated with non-specific binding and capture of non-targeted cells (a problem associated with the aforementioned affinity capture protocols)

Keystroke and Touch-dynamics Based Authentication for Desktop and Mobile Devices

The most commonly used system on desktop computers is a simple username and password approach which assumes that only genuine users know their own credentials. Once broken, the system will accept every authentication trial using compromised credentials until the breach is detected. Mobile devices, such as smart phones and tablets, have seen an explosive increase for personal computing and internet browsing. While the primary mode of interaction in such devices is through their touch screen via gestures, the authentication procedures have been inherited from keyboard-based computers, e.g. a Personal Identification Number, or a gesture based password, etc.;This work provides contributions to advance two types of behavioral biometrics applicable to desktop and mobile computers: keystroke dynamics and touch dynamics. Keystroke dynamics relies upon the manner of typing rather than what is typed to authenticate users. Similarly, a continual touch based authentication that actively authenticates the user is a more natural alternative for mobile devices.;Within the keystroke dynamics domain, habituation refers to the evolution of user typing pattern over time. This work details the significant impact of habituation on user behavior. It offers empirical evidence of the significant impact on authentication systems attempting to identify a genuine user affected by habituation, and the effect of habituation on similarities between users and impostors. It also proposes a novel effective feature for the keystroke dynamics domain called event sequences. We show empirically that unlike features from traditional keystroke dynamics literature, event sequences are independent of typing speed. This provides a unique advantage in distinguishing between users when typing complex text.;With respect to touch dynamics, an immense variety of mobile devices are available for consumers, differing in size, aspect ratio, operating systems, hardware and software specifications to name a few. An effective touch based authentication system must be able to work with one user model across a spectrum of devices and user postures. This work uses a locally collected dataset to provide empirical evidence of the significant effect of posture, device size and manufacturer on user authentication performance. Based on the results of this strand of research, we suggest strategies to improve the performance of continual touch based authentication systems

IMMERSED BOUNDARY CONDITIONS METHOD FOR COMPUTATIONAL FLUID DYNAMICS PROBLEMS

This dissertation presents implicit spectrally-accurate algorithms based on the concept of immersed boundary conditions (IBC) for solving a range of computational fluid dynamics (CFD) problems where the physical domains involve boundary irregularities. Both fixed and moving irregularities are considered with particular emphasis placed on the two-dimensional moving boundary problems. The physical model problems considered are comprised of the Laplace operator, the biharmonic operator and the Navier-Stokes equations, and thus cover the most commonly encountered types of operators in CFD analyses. The IBC algorithm uses a fixed and regular computational domain with flow domain immersed inside the computational domain. Boundary conditions along the edges of the time-dependent flow domain enter the algorithm in the form of internal constraints. Spectral spatial discretization for two-dimensional problems is based on Fourier expansions in the stream-wise direction and Chebyshev expansions in the normal-to-the-wall direction. Up to fourth-order implicit temporal discretization methods have been implemented. The IBC algorithm is shown to deliver the theoretically predicted accuracy in both time and space. Construction of the boundary constraints in the IBC algorithm provides degrees of freedom in excess of that required to formulate a closed system of algebraic equations. The ‘classical BBC formulation’ works by retaining number boundary constraints that are just sufficient to form a closed system of equations. The use of additional boundary constraints leads to the ‘over-determined formulation’ of die IBC algorithm. Over- determined systems are explored in order to improve the accuracy of the IBC method and to expand its applicability to more extreme geometries. Standard direct over-determined solvers based on evaluation of pseudo-inverses of the complete coefficient matrices have been tested on three model problems, namely, the Laplace equation, the biharmonic equation and the Navier-Stokes equations. In all cases tested the over-determined m formulations based on standard solvers were found to improve the accuracy and the range o f applicability o f the IBC method. Efficient linear solvers suitable for the spectral implementation of the IBC method have been developed and tested in the context of two-dimensional steady and unsteady Stokes flow in the presence of fixed boundary irregularities. These solvers can work with the classical as well as the over-determined formulations of the method. Significant acceleration of the computations as well as significant reduction of the memory requirements have been accomplished by taking advantage of the structure of the coefficient matrix resulting from the implementation of the IBC algorithm. Performances o f the new solvers have been compared with the standard direct solvers and are shown to be of up to two orders of magnitude better. It has been determined that the new methods are by at least an order of magnitude faster than the iterative methods while removing restrictions based on the convergence criteria and thus expanding the severity of the geometries that can be dealt with using the IBC algorithm. The performance of the IBC method combined with the new solvers has been compared with the performance of a method based on the generation of the boundary conforming grids, and is found to be better by at least two orders of magnitude. Application of the new solvers to the unsteady problems also results in performance improvement of up to two orders of magnitude. The specialized solvers applied to the over-determined formulation is shown to be at least two orders of magnitude faster than their standard counterparts while capable of extending the range of applicability of the IBC algorithm by 50%-70% for the Stokes flow problem. The concept of the specialized solvers has been extended to solve two-dimensional moving boundary problems described by the Navier-Stokes equations, where the new solver has been shown to result in a significant acceleration of computations as well as substantial reduction in memory requirements. The conceptual aspects of extending the IBC algorithm for solving three-dimensional problems have been presented using the vorticity-velocity formulation of the three- dimensional Navier-Stokes equations. Test results on the implementation of the IBC algorithm for three-dimensional problems are discussed in the context of heat diffusion IV problems in the presence of fixed as well as moving boundaries. The algorithm is shown to be spectrally-accurate in space and capable of delivering theoretically predicted accuracy in time for the different test problems. Given a potentially large size of the resultant linear algebraic system, various methods that take advantage of the special structure of the coefficient matrix have been explored in search for an efficient solver, including two versions of the specialized direct solver as well as serial and parallel iterative solvers. Both versions of the specialized direct solver have been shown to be more computationally efficient than the other solution methods. Possible applications of the IBC algorithm for analyzing physical problems have also been presented. The advantage of using IBC algorithm is illustrated by considering its application to two physical problems, which are - i) analysis of the effects of distributed roughness on friction factor and ii) analysis of traveling wave instability in wavy channels. These examples clearly show the attractiveness of the IBC algorithm for studying effects of a large array of boundary geometries on the flow field

Why The Green Revolution Was Short Run Phenomena In The Development Process Of Pakistan: A Lesson For Future

Agriculture is the most important sector of Pakistan’s economy. It provides food and fibre, source of scarce foreign exchange earning and a market for industrial goods. In 1960s various policy measures were taken for Agriculture development. The research tries to examine various issues related to this sector. Focus of the research, however, is to analyze the role of Green Revolution in the development process of Pakistan and its short and long term impact on the economy. The paper analyzes weaknesses due to which the Green Revolution remained a shortterm phenomena. The contributing factors of Green Revolution and other supporting institutions are also discussed. The findings of this study show that the Green Revolution increased agriculture production and employment level. It also had impact on distribution of income and the social and political environment in the country. However, there were certain policy gaps due to which the impact of Green Revolution remained a short-term phenomena.

IAA production and maize crop growth promoting potential of endophyte Aspergillus niger (AO11) under salt stress

Maize is cultivated under a broad range of soil conditions and environments. Maize is slightly vulnerable to salt stress and therefore it is seriously affected by soil salinity all over the world. Recognizing the responses of maize to salt stress and making a good strategy to overcome this problem could aid to develop solutions in saline areas to improve maize productivity. We investigated in this research the impacts, tolerance and salt stress management in corn. Many endophytic fungi can produce the Indole-3-acetic acid (IAA) is known for their role in plant growth and development both with and without salt stress conditions. The current study was focused on the production of IAA by endophytic fungi (Aspergillus niger) and maize seeds germination and promotion of seedling growth and vigor. In order to evaluate the defense response of maize plant, in relation to A. niger, an experiment was designed with three replications of treatments (control, salt stressed, salt stressed inoculated with A. niger, and only A. niger inoculated plants. It was determined that A. niger has the ability to produce the IAA in NaCl and KCl stress peaking 53 μg/ml and was not significantly by alternating the nitrogen and carbon sources in the nutrient broth but increasing the tryptophan concentration raised its production level. High concentration stress of sodium chloride and potassium chloride decrease maize plant seeds germination percentage, shoot and root length also affected the fresh and dry weight of maize. A. niger improves salt resistance in maize and also increased the germination percentage up to 30%, also improved the chlorophyll level and it was proved an effective approach for improving maize germination and growth under salt stress