Compressive forces causing rod buckling in sucker rod pumps and using sinker bars to prevent buckling

Sucker rod pumps has been the most commonly used pumps in the petroleum industry. Therefore, many studies associated with sucker rods focuses on maximizing the rod life. Rod buckling is a leading problem which causes concentrated wear on tubing wall, immediate failure in rod strings, and shortens fatigue life of the string. This study fundamentally consists of a review of the literature on compressive forces causing rod buckling in sucker rod pumps and using sinker bars to prevent buckling. The study initially addresses defining rod buckling, and then continues with the studies on analyzing the static forces acting near pump in the literature. Subsequently, the critical loads causing rod buckling, and the various approximations to estimate these critical loads are discussed. Then, the comparisons of the measured and calculated critical loads in the literature are presented. Next, the two of the most commonly experienced buckling types in the sucker pumps, sinusoidal buckling and helical buckling, are discussed. An example study on developing a model to estimate compressive forces acting on the pump plunger is reviewed to illustrate the importance of the parameters, such as surface roughness of pump, valve diameter, and pump geometry. Lastly, using sinker bar which is the most practiced method in the industry to prevent rod buckling is extensively discussed and demonstrated.Petroleum and Geosystems Engineerin

X-ray Flux and Pulse Frequency Changes of Three High Mass X-ray Binary Pulsars: Vela X-1, GX 301-2 and OAO 1657-415

Using archival BATSE (Burst and Transient Source Experiment) 20-60 keV band X-ray flux and pulse frequency time series, we look for correlations between torque, luminosity and specific angular momentum for three high mass X-ray binary pulsars Vela X-1, GX 301-2 and OAO 1657-415. Our results show that there is no correlation between pulse frequency derivative and flux which may be an indication of the absence of stable prograde accretion disk. From the strong correlation of specific angular momentum and torque, we conclude that the accretion geometry changes continuously as suggested by the hydrodynamic simulations(Blondin et al. 1990).Comment: 14 pages, 9 figures, accepted for publication in Astronomy and Astrophysic

Convex Optimization Approaches for Blind Sensor Calibration using Sparsity

We investigate a compressive sensing framework in which the sensors introduce a distortion to the measurements in the form of unknown gains. We focus on blind calibration, using measures performed on multiple unknown (but sparse) signals and formulate the joint recovery of the gains and the sparse signals as a convex optimization problem. We divide this problem in 3 subproblems with different conditions on the gains, specifially (i) gains with different amplitude and the same phase, (ii) gains with the same amplitude and different phase and (iii) gains with different amplitude and phase. In order to solve the first case, we propose an extension to the basis pursuit optimization which can estimate the unknown gains along with the unknown sparse signals. For the second case, we formulate a quadratic approach that eliminates the unknown phase shifts and retrieves the unknown sparse signals. An alternative form of this approach is also formulated to reduce complexity and memory requirements and provide scalability with respect to the number of input signals. Finally for the third case, we propose a formulation that combines the earlier two approaches to solve the problem. The performance of the proposed algorithms is investigated extensively through numerical simulations, which demonstrates that simultaneous signal recovery and calibration is possible with convex methods when sufficiently many (unknown, but sparse) calibrating signals are provided

Balancing Sparsity and Rank Constraints in Quadratic Basis Pursuit

We investigate the methods that simultaneously enforce sparsity and low-rank structure in a matrix as often employed for sparse phase retrieval problems or phase calibration problems in compressive sensing. We propose a new approach for analyzing the trade off between the sparsity and low rank constraints in these approaches which not only helps to provide guidelines to adjust the weights between the aforementioned constraints, but also enables new simulation strategies for evaluating performance. We then provide simulation results for phase retrieval and phase calibration cases both to demonstrate the consistency of the proposed method with other approaches and to evaluate the change of performance with different weights for the sparsity and low rank structure constraints

Overconfidence and financial decision making - the impact of financial risk tolerance on confidence judgments

A wide range of research has shown that people are overconfident in their judgments displaying a contradiction to modern economic theories supposing individuals as rational agents with the goal of maximizing expected utility and minimizing risk exposure. However, overconfident agents overestimate their judgments and expertise or presume themselves to be better than their peers leading those individuals to exhibit a higher willingness to engage in risky behaviors. So, it can be expected that overconfidence and financial risk tolerance are positively associated with each other. A sample consisting of 137 people was analyzed with the result that there is no evidence supporting this hypothesis, neither in a group level nor on an individual basis. The degrees of overconfidence and risk tolerance are not correlated. Nevertheless, financial risk tolerance has a significant positive correlation on observed level of confidence, whereas accuracy of judgments is not significantly affected by the degree of risk tolerance

Three essays in political economy

This is a comprehensive study of the U.S. political process from the perspective of media, voters and candidates. In the first chapter, I analyze the sources of media bias. In the second chapter, I focus on economically self-interested voting. The third chapter studies the effectiveness of negative campaigning. In the next three paragraphs, I summarize these three chapters With the advent of internet, many U.S. metropolitan areas have seen newspaper closures due to declining revenues. This provides the researcher with an opportunity to analyze the microeconomic sources of media bias. This paper uses a large panel data set of newspaper archives for 102 newspapers over 238 months (1990-2009). I find that, after controlling for the unemployment rate and the change in unemployment rate, conservative newspapers report 19% more unemployment news when the President is a Democrat rather than a Republican, before the closure of a rival newspaper in the same media market. This effect is 12% for liberal newspapers. After the closure, these numbers are 3.5% and 1%, respectively. This moderation of media bias after closure of a rival newspaper stands as newspaper size, newspaper fixed-effects or metropolitan area fixed-effects are included. I also find that newspapers in smaller metropolitan areas have a larger moderation in their bias. My findings provide support for theories in which media-bias is demand-driven, as surviving newspapers aim to increase their sales by gaining the former readers of a closed newspaper in the same media market. A long literature investigates the influence of income on voting behavior, but it focuses primarily on presidential elections. We ask whether economically self-interested voting is unique to the presidential elections, or if it also extends to House, Senate and gubernatorial elections. In addition, for each office, we look for the presence of absolute income effects and relative income effects. Voters do indeed appear to vote in an economically self-interested manner for each office, but we show that in all elections but presidential elections, this effect is largely generated by the correlation of income with political issue stances. Controlling for voter stances on a number of social and economic issues, there is little evidence of partisan differences in voting according to income outside of presidential elections. Our findings at once support previous studies, but illustrate that presidential elections are very much a special case in US socio-political behavior. Political candidates commonly use negative TV ads to attack their opponents. In very limited research on effectiveness of negative campaigning, endogeneity problem has not been addressed and trait ads were not separated from issue ads. In this project, I use instrumental variables estimates of the effectiveness of negative campaigning and distinguish between issue ads and trait ads. Using 162 U.S. Senate Elections between 1998 and 2008, I find that negative issue campaigning is effective for challengers in significantly reducing the incumbent???s vote, although this effect is not large enough to change the election outcome in lopsided elections. In competitive elections, I find that challenger???s negative issue ads can change the election outcome. I do not find any significant effects of negative issue ads by an incumbent, except for competitive elections. Both incumbents and challengers hurt themselves if they resort to negative trait ads (personal attacks)

Modeling emergency management data by UML as an extension of geographic data sharing model: AST approach

Applying GIS functionality provides a powerful decision support in various application areas and the basis to integrate policies directed to citizens, business, and governments. The focus is changing toward integrating these functions to find optimal solutions to complex problems. As an integral part of this approach, geographic data sharing model for Turkey were developed as a new approach that enables using the data corporately and effectively. General features of this model are object-oriented model, based on ISO/TC211 standards and INSPIRE Data Specifications, describing nationwide unique object identifiers, and defining a mechanism to manage object changes through time. The model is fully described with Unified Modeling Language (UML) class diagram. This can be a starting point for geographic data providers in Turkey to create sector models like Emergency Management that has importance because of the increasing number of natural and man-made disasters. In emergency management, this sector model can provide the most appropriate data to many "Actors" that behave as emergency response organizations such as fire and medical departments. Actors work in "Sectors" such as fire department and urban security. Each sector is responsible for "Activities" such as traffic control, fighting dire, emission, and so on. "Tasks" such as registering incident, fire response, and evacuating area are performed by actors and part of activity. These tasks produce information for emergency response and require information based on the base data model. By this way, geographic data models of emergency response are designed and discussed with "Actor-Sector-Activity-Task" classes as an extension of the base model with some cases from Turkey

Performance Analysis of NAND Flash Memory Solid-State Disks

As their prices decline, their storage capacities increase, and their endurance improves, NAND Flash Solid-State Disks (SSD) provide an increasingly attractive alternative to Hard Disk Drives (HDD) for portable computing systems and PCs. HDDs have been an integral component of computing systems for several decades as long-term, non-volatile storage in memory hierarchy. Today's typical hard disk drive is a highly complex electro-mechanical system which is a result of decades of research, development, and fine-tuned engineering. Compared to HDD, flash memory provides a simpler interface, one without the complexities of mechanical parts. On the other hand, today's typical solid-state disk drive is still a complex storage system with its own peculiarities and system problems. Due to lack of publicly available SSD models, we have developed our NAND flash SSD models and integrated them into DiskSim, which is extensively used in academe in studying storage system architectures. With our flash memory simulator, we model various solid-state disk architectures for a typical portable computing environment, quantify their performance under real user PC workloads and explore potential for further improvements. We find the following: * The real limitation to NAND flash memory performance is not its low per-device bandwidth but its internal core interface. * NAND flash memory media transfer rates do not need to scale up to those of HDDs for good performance. * SSD organizations that exploit concurrency at both the system and device level improve performance significantly. * These system- and device-level concurrency mechanisms are, to a significant degree, orthogonal: that is, the performance increase due to one does not come at the expense of the other, as each exploits a different facet of concurrency exhibited within the PC workload. * SSD performance can be further improved by implementing flash-oriented queuing algorithms, access reordering, and bus ordering algorithms which exploit the flash memory interface and its timing differences between read and write requests