Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

There are many problems associated with night shift work, involving both the disruption of social activities and the desynchrony between internal biological clock timing and the forced regimen. Both short term problems (e.g. sleep deficiency, reduced alertness and reduced performance) and potential long term problems (e.g. coronary heart disease and diabetes) may be critically dependent on whether or not the worker is able to adapt to the shift regimen. In the first of two baseline studies, the 6-sulphatoxymelatonin rhythms of offshore oil workers on a two-week 12-hour night shift (1800h to 0600h) were shown to adapt to the regimen within the first seven days of the shift. The rates of phase shift (mean +/- sem) were 1.51 +/- 0.16 h/day (n=5), 1.32 +/- 0.41 h/day (n=5) and 1.77 +/- 0.31 h/day (n=17) for a winter drill crew, winter maintenance crew and summer maintenance crew respectively. The rate of adaptation was not significantly affected by the type of work conducted or the season. The second baseline study assessed the 6-sulphatox-5-onelatonin rhythms of offshore drill crews on a one-week day shift (1200h - 0000h), one-week night shift (0000h - 1200h) 'swing' shift. A crew studied in winter showed no change in their 6-sulphatoxymelatonin rhythm during night shift, while a crew studied in spring showed a significant phase advance to an acrophase position of 0051h +/-1.7 hours (mean +/- sem). This data, together with that of the first baseline study, indicate that both the type of shift and the season influence the direction and degree of adaptation. A simulation study was conducted to assess the hormonal and metabolic response to a test meal during the first night of night shift (1800h to 0600h). Both plasma glucose and insulin levels were elevated on night shift compared to day shift, suggesting a degree of glucose intolerance during this period. Treatment with bright light (1500 lux) throughout the night shift reduced the glucose intolerance observed and also lowered plasma triacylglycerol levels. The use of exogenous melatonin to help shift workers acclimatise to day shift following night shift was examined. Exogenous melatonin significantly increased sleep duration compared to placebo. There was also evidence of increased daytime napping and stabilization of sleep onset time under this treatment. While no specific adaptation rates could be observed, exogenous melatonin did not appear to have an adverse effect on the adaptation of the melatonin and alertness rhythms when taken at the desired bedtime. The data clearly show that adaptation of the melatonin rhythm to night shift is possible in certain environments. Further evidence of the deleterious effects of night shift on metabolic and hormonal responses to a nighttime meal has been observed, but the use of bright light treatment may be a potential solution to this problem. While the benefits of exogenous melatonin treatment on sleep may be of use offshore, an increased incidence of daytime napping, observed during melatonin treatment, may be of concern for its use in an offshore environment.

The massive rise in Computer Science enrollments in both traditional classroom courses and in Massively Open Online Courses (MOOCs) shows the enormous opportunities in engaging students to learn programming. While the number of students in CS courses continues to increase, there has been no concomitant increase in the number of instructors for such courses. This leads to a completely lopsided learning environment where the already-stretched instructor is pressed to spend more time on ancillary tasks like grading and course bookkeeping. CodeWorkout is an online drill-and-practice system with course management features that aims to address these issues. CodeWorkout hosts an online repository of programming questions that instructors can incorporate into their courses. It also provides instructors with a facility to create their own programming questions so that exercises can be tailored according to the needs of the class. CodeWorkout has an open gradual engagement model that allows students who are not enrolled in a course to use it. CodeWorkout also creates an open environment for instructors to collaborate by sharing exercises that they create. CodeWorkout has been used in four courses at Virginia Tech. It has been shown to significantly improve the student's skills in introductory programming through providing a number of online practice questions. / Master of Science

This report presents the work on improving the lateral stability of the seed coulters of Väderstad seed drill model Spirit. The work lasted ten weeks and was carried out at Väderstad AB spring 2019. The basic problem was analyzed with a number of different methods, and tests were carried out both in the field and in the test rig. With the results from these, it was found that the suspension of the seed coulters allowed both torsional and lateral movements at low loads.   The work started with a root cause analysis which was then used to produce a requirement specification. This was then used to develop concepts. After evaluation, the best concepts were selected, analyzed, modeled and calculated. When the concepts were deemed to be sufficiently functional, several manufacturing analyses were made to assess the suitability for serial production.   Three concepts were developed. One is a final concept that can be mounted directly on existing machines in the form of injection-molded plastic blocks on the seed coulters. One is a concept for future year models were flanges are mounted on the fall of the seed coulters. This concept is available in two parts, either in the form of a welded steel profile or as part of a sand cast reconstruction of the seed coulters. The third and final concept is a reconstruction of the machine's seed coulters with a spring to control the bill pressure. In addition, a method for evaluating the side stability of the seed coulters has been developed.   The reason for the Nordic model's problems is that the seed coulters tend to track the grooves of the fertilizer carriers. This can be solved by having the seed coulters support each other in the lateral direction.   As a continued work, a more thorough examination of the sand cast flange concept is recommended. This is in line with Väderstad's philosophy of making built to last products.

Wireline formation testers are widely used to measure in-situ fluid pressure, to retrieve reservoir fluid samples, and to estimate formation mobility. However, formation-tester measurements are invariably influenced by mud-filtrate invasion due to drilling overbalance pressure, thereby affecting the acquisition of uncontaminated fluid samples and the estimation of in-situ petrophysical properties. Moreover, in cases of stress-sensitive formations, rock mechanical deformation may take place due to the combined effects of in-situ stress, wellbore stress imposed by mud overbalance, and wellbore pressure exerted by the formation tester itself. The latter deformation causes near-borehole perturbations of porosity and permeability that are evidenced by pressure transients measured during build-up and shut-in stages of formation testing, especially when using dual-packer pressure probes. If unaccounted for, such perturbations can also bias the estimation of in-situ fluid and petrophysical properties. Conversely, the detection and quantification of elastic mechanical deformation effects on measured pressure transients can be used to infer the underlying rock elastic and petrophysical properties of the stressed formation. The purpose of this dissertation is twofold: (a) to quantify the relative effects of mud-filtrate invasion and geomechanical deformation on pressure-transient measurements acquired with dual-packer formation testers, with special emphasis on the appraisal of near-borehole porosity and permeability enhancement due to elastic mechanical deformation, and (b) to develop a new method to estimate elastic and petrophysical properties of rock formations from dual-packer pressure transients acquired in mechanically deformable rocks. Numerical simulations of mud-filtrate invasion are performed with an axialsymmetric two-phase (water-oil) method that enforces the specific boundary and source conditions of a wellbore that penetrates horizontal layers. Simulations are performed in a cylindrical system of coordinates using finite differences together with an implicit-pressure, explicit-saturation time-marching approach that also incorporates the dynamic conditions of immiscible mudcake growth due to filtration of solids at the wellbore. Laboratory experiments are conducted to further study pressure transients due to formation testing in the presence of invasion with water-base mud. Experiments include the effects of both mud circulation and mudcake on pressure-transient measurements and are performed on a variety of rock-core samples. Measurements are successfully validated with both the developed simulator and a commercial simulator, thereby lending credence to the assumed model of dynamic solid filtration. The developed mud-filtrate fluid-flow simulator is coupled with a finite-element code that assumes 2D axial-symmetric linear elasticity to quantify geomechanical deformation. Coupling of mechanical deformation with variations of porosity and permeability assumes a staggered-in-time, iteratively coupled volumetric model. We assume a dual-packer formation tester to quantify elastic deformation effects in stress-sensitive formations as a preamble to estimating in-situ elastic and petrophysical properties. It is shown that near-wellbore spatial variations of porosity and permeability due to mechanical deformation can bias the corresponding pressure-transient measurements acquired with the dual-packer formation-tester. The degree of biasing depends on the rigidity of the stressed formation. Finally, we develop a method to estimate in-situ petrophysical and elastic rock properties from pressure-transient measurements acquired with formation-testers in mechanically deformable rocks. Petrophysical and elastic properties will change in both time and space depending on the time evolution of the conditions that influence mechanical deformation. We use a commercial reservoir simulator to calculate pressure transients due to fluid pumpout in the presence of both invasion and mechanical deformation. A pre-stressed initial condition due to mud overbalance is assumed with incremental deformation due to surface force applied by the packers or probes, and active flow imposed by the formation-tester. In so doing, we consider pressure data sets acquired with both flow and observation probes during draw-down and build-up periods. For cases where a-priori information can be sufficiently constrained, our estimation method provides reliable and accurate estimates of petrophysical and elastic properties in the presence of moderate levels of random noise. / text

In an effort to increase machining efficiency and minimize costs, research into tool condition monitoring (TCM) systems has focused on developing methods to allow for unmanned machining. For drilling processes, such systems typically use indirect approaches to monitoring the tool condition by measuring spindle torque and feed force as well as vibrations including acoustic emission (AE – mechanical vibrations faster than 100 kHz). This project aimed to advance the state-of-the-art in the area of TCM by developing a method to detect sudden tool failures in large diameter (> 25 mm) indexable insert drills. This project was a continuation of the research conducted by Mr. R. Griffin (a former MSc student), who developed a model capable of predicting long term wear trends in indexable insert drills [1]. Notably, his model was unable to react to sudden tool breakage due to tool chipping, which was addressed by this project as presented in this thesis. In order to develop and train models able to detect sudden tool failure, an experiment was developed and installed in the field of the industry partner of this project. The experiment’s main feature was a pair of AE sensors added to the existing torque and force sensors. On this setup, experiments were conducted by drilling 2251 holes in workpieces using indexable insert drills with or without the insert breaking. When drilling holes without the insert breaking, the holes were named as good ones; and when drilling holes with the insert breaking they were named as bad holes. During the drilling process, data was collected from current sensors attached to the spindle motor and feed motor as well as from an AE sensor on the spindle and on the workpiece. From the signals from the spindle motor current and feed motor current sensors, algorithms were developed to identify and divide the signals of drilling a hole into different sections of the drilling cycle (i.e. entrance, steady-state, exit, etc.). Steady-state time-domain features were extracted from the sensor signals measured for all holes drilled in the experiments and the extracted features were used to train and test the classifier models. These models were cross validated to determine which type of model was the best fit for the drilling data collected. The results from the classifier models show that most of the classifiers tested have the ability to identify sudden tool breakage based on the data recorded in the present study, with varying degrees of success. The naïve Bayes classifier was able to detect the most failures but suffered from a large number of falsely detected failures. Both the classification tree and linear discriminant analysis classifiers had lower failure detection rates than the naïve Bayes classifier, but did not suffer from the same amount of false positives; as such, these two classifiers had higher overall classification rates than the naïve Bayes. These results suggest that classification tree and linear discriminant analysis methods are better suited for the drilling application and that the time-domain features should be complemented by others, such as the features extracted from the frequency domain, to accurately diagnose the tool condition. Future research should focus on extracting frequency and time-frequency domain features as these features might contain more information on tool condition. In addition, methods of examining features at the entrance and exit of the holes should be investigated as these two points in the drilling cycle are the most prone to sudden tool failure.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

2 pp. / Self seeding, planting equipment, planting into stubble, row spacing, bed vs flat planting, planting into moisture vs. irrigation up, and planting direction are discussed.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.