351 |
Dark and luminous matter in bright spiral galaxiesKassin, Susan Alice Joan 12 October 2004 (has links)
No description available.
|
352 |
The Tully-Fisher Relation, its residuals, and a comparison to theoretical predictions for a broadly selected sample of galaxiesPizagno, James Lawrence, II 13 September 2006 (has links)
No description available.
|
353 |
Palaeomagnetic Evidence for Anti-Clockwise Rotation of Rouyn-Noranda Structural Block, Quebec, Canada / Palaeomagnetic Rotations in the Abitibi BeltAmin, Mohammad 06 1900 (has links)
The Rouyn-Noranda area in the center of the Abitibi subprovince is composed of comparatively unmetamorphosed Archean volcanics of Blake River Group (ERG). Rouyn-Nornada is one of the lozenge shaped structural blocks in the area bounded by the Porcupine Destor Fault (PDF) zone and the Larder Lake Caddilac Fault (LCF) zone. 160 samples were collected from 29 different sites selected to lie in the center of the block, at or near the PDF zone and accross the PDF zone in the neighboring lozenge.
Stable magnetizations have been obtained from the central relatively unstrained parts of the lozenges. These magnetizations show some improvement in precision statistics after structural corrections implying that they are pre-folding and probably Archean in age. Sites along the PDF zone show scattered magnetizations, which do not agree at sample or site level. The Zone I (Sites in the center of the Rouyn-Noranda block) structurally corrected mean direction (D=154.0, I=-95.0, k=19.0, a95 =19.0, N=6 sites) differ from the Zone III (Sites from the center of the adjacent block) mean direction (D=214.0, I=-49.0, k=16.0, a95 =92.0) by 60+/-37° implying that the Rouyn-Norand block have rotated anti-clockwise by 60+/-37° about a vertical axis relative to the adjacent structural block. / Thesis / Master of Science (MS)
|
354 |
The effects of fertilization and crop rotations on rainfed barley development, growth and yields, in a semi-arid mediterranean-type climate /Rached, E. M. January 1986 (has links)
No description available.
|
355 |
Moment resistance and rotation capacity of semi-rigid composite connections with precast hollowcore slabs.Fu, F., Lam, Dennis, Ye, J. January 2010 (has links)
Semi-rigid composite connections with precast hollowcore slabs are a newly developed technique with few applications in current construction practice. The research on the structural behaviour of this new type of connection is limited, with no existing method available to predict its important characteristics such as moment and rotation capacities. In this paper, based on the parametric studies of the three-dimensional finite element model and full-scale tests, analytical methods to calculate the moment and rotation capacity of this type of composite joint are proposed. A comparison between the proposed calculation method and the full-scale test results was made, and good agreement was obtained.
|
356 |
Analysis of Worker Assignment Policies on Production Line Performance Utilizing a Multi-skilled WorkforceMcDonald, Thomas N. 18 March 2004 (has links)
Lean production prescribes training workers on all tasks within the cell to adapt to changes in customer demand. Multi-skilling of workers can be achieved by cross-training. Cross-training can be improved and reinforced by implementing job rotation. Lean production also prescribes using job rotation to improve worker flexibility, worker satisfaction, and to increase worker knowledge in how their work affects the rest of the cell. Currently, there is minimal research on how to assign multi-skilled workers to tasks within a lean production cell while considering multi-skilling and job rotation.
In this research, a new mathematical model was developed that assigns workers to tasks, while ensuring job rotation, and determines the levels of skill, and thus training, necessary to meet customer demand, quality requirements, and training objectives. The model is solved using sequential goal programming to incorporate three objectives: overproduction, cost of poor quality, and cost of training. The results of the model include an assignment of workers to tasks, a determination of the training necessary for the workers, and a job rotation schedule. To evaluate the results on a cost basis, the costs associated with overproduction, defects, and training were used to calculate the net present cost for one year. The solutions from the model were further analyzed using a simulation model of the cell to determine the impact of job rotation and multi-skilling levels on production line performance. The measures of performance include average flowtime, work-in-process (WIP) level, and monthly shipments (number produced).
Using the model, the impact of alternative levels of multi-skilling and job rotation on the performance of cellular manufacturing systems is investigated. Understanding the effect of multi-skilling and job rotation can aid both production managers and human resources managers in determining which workers need training and how often workers should be rotated to improve the performance of the cell. The lean production literature prescribes training workers on all tasks within a cell and developing a rotation schedule to reinforce the cross-training. Four levels of multi-skilling and three levels of job rotation frequency are evaluated for both a hypothetical cell and a case application in a relatively mature actual production cell. The results of this investigation provide insight on how multi-skilling and job rotation frequency influence production line performance and provide guidance on training policies.
The results show that there is an interaction effect between multi-skilling and job rotation for flowtime, work-in-process, in both the hypothetical cell and the case application and monthly shipments in the case application. Therefore, the effect of job rotation on performance measures is not the same at all levels of multi-skilling thus indicating that inferences about the effect of changing multi-skilling, for example, should not be made without considering the job rotation level. The results also indicate that the net present cost is heavily influenced by the cost of poor quality. The results for the case application indicated that the maturity level of the cell influences the benefits derived from increased multi-skilling and affects several key characteristics of the cell. As a cell becomes more mature, it is expected that the quality levels increase and that the skill levels on tasks normally performed increase. Because workers in the case application already have a high skill level on some tasks, the return on training is not as significant. Additionally, the mature cell has relatively high quality levels from the beginning and any improvements in quality would be in small increments rather than in large breakthroughs.
The primary contribution of this research is the development of a sequential goal programming worker assignment model that addresses overproduction, poor quality, cross-training, and job rotation in order to meet the prescription in the lean production literature of only producing to customer demand while utilizing multi-skilled workers. Further contributions are analysis of how multi-skilling level and job rotation frequency impact the performance of the cell. Lastly, a contribution is the application of optimization and simulation methods for comprehensively analyzing the impact of worker assignment on performance measures. / Ph. D.
|
357 |
Local Correlation: Implementation and Application to Molecular Response PropertiesRuss, Nicholas Joel 26 April 2006 (has links)
One of the most promising methods for surmounting the high-degree polynomial scaling wall associated with electron correlating wave function methods is the local correlation technique of Pulay and Saebø. They have proposed using a set of localized occupied and virtual orbitals free of the canonical constraint commonly employed in quantum chemistry, resulting in a method that scales linearly (in the asymptotic limit) with molecular size. Pulay and Saeb$oslash; first applied their methods to configuration interaction and later to M$oslash;ller-Plesset perturbation theory. Werner et al. have have extended the local correlation scheme of Pulay and Saeb$oslash; to coupled-cluster theory.
One of the pitfalls of the local correlation methods developed by Pulay and Saeb$oslash; is the dependence of domain selection on the molecular geometry. In other words, as the geometry changes the domain structure of the local correlation calculation can change also, leading to discontinuities in the potential energy surface. We have examined the size of these discontinuities for the homolytic bond cleavage of fluoromethane and the heterolytic bond dissociation of singlet ketene and propadienone.
Properties such as polarizabilities and optical rotation are realized through linear response theory, where the Hamiltonian is subject to an external perturbation and the wave function is allowed to respond to the applied perturbation. Within the context of local correlation it is necessary to understand how the domain structure alters in response to an applied perturbation. We have proposed using solutions to the CPHF equations (coupled-perturbed Hartree-Fock) in order to predict the correlation response to an applied perturbation. We have applied this technique to the calculation of polarizabilities, with very favorable results, and also to optical rotation, with mixed results. / Ph. D.
|
358 |
Ab initio Calculations of Optical RotationTam, Mary Christina 02 May 2006 (has links)
Coupled cluster (CC) and density functional theory (DFT) are highly regarded as robust quantum chemical methods for accurately predicting a wide variety of properties, such as molecular structures, thermochemical data, vibrational spectra, etc., but there has been little focus on the theoretical prediction of optical rotation. This property, also referred to as circular birefringence, is inherent to all chiral molecules and occurs because such samples exhibit different refractive indices for left- and right- circularly polarized light. This thesis focuses on the theoretical prediction of this chiroptic property using CC and DFT quantum chemical models. Several small chiral systems have been studied, including (S)-methyloxirane, (R)-epichlorohydrin, (R)-methylthiirane, and the conformationally flexible molecules, (R)-3-chloro-1-butene and (R)-2-chlorobutane. All predicted results have been compared to recently published gas-phase cavity ringdown polarimetry data. When applicable, well-converged Gibbs free energy differences among confomers were determined using complete-basis-set extrapolations of CC energies in order to obtain Boltzmann-averaged specific rotations. The overall results indicate that the theoretical rotation is highly dependent on the choice of optimized geometry and basis set (diffuse functions are shown to be extremely important), and that there is a large difference between the CC and DFT predicted values, with DFT usually predicting magnitudes that are larger than those of coupled cluster theory. / Ph. D.
|
359 |
Assessing Negative Side Effects in Virtual EnvironmentsMcGee, Michael K. 11 February 1998 (has links)
Virtual environment (VE) systems have been touted as exciting new technologies with many varied applications. Today VEs are used in telerobotics, training, simulation, medicine, architecture, and entertainment. The future use of VEs seems limited only by the creativity of its designers. However, as with any developing technology, some difficulties need to be overcome. Certain users of VEs experience negative side effects from being immersed into the graphically rendered virtual worlds. Some side effects that have been observed include: disorientation, headaches, and difficulties with vision. These negative side effects threaten the safety and effectiveness of VE systems.
Negative side effects have been found to develop in a variety of environments. The research focus on VE side effects thus far has been on the symptoms and not the causes. The main goals of this research is fourfold: 1) to compare a new measure for side effects with established ones; 2) begin analyzing the causes of side effects with an analysis of head-tracking; 3) to examine any adaptation that may occur within a session and between days of a session; and, 4) to examine possible predictors for users who may experience side effects.
An experiment was conducted using two different VEs with either head-tracking on or head-tracking off over four days. A questionnaire, a balance test, a vision test, and magnitude estimations of side effects were used to assess the incidence and severity of sickness experienced in the VEs. Other assessments, including a mental rotation test, perceptual style, and a questionnaire on pre-existing susceptibility to motion sickness were administered. All factors were analyzed to determine what their relationships were with the incidence and severity of negative side effects that result from immersion into the VEs.
Results showed that head-tracking induces more negative side effects than no head-tracking. The maze task environment induces more negative side effects than the office task environment. Adaptation did not occur from day to day throughout the four testing sessions. The incidence and severity of negative side effects increased at a constant rate throughout the 30 minute immersive VE sessions, but did not show any significant changes from day to day. No evidence was found for a predictor that would foretell who might be susceptible to motion sickness in VEs. / Master of Science
|
360 |
Analysis of Lumbar Spine Kinematics during Trunk Flexion and Extension MotionsLee, Minhyung 30 January 2006 (has links)
The effectiveness of exercise has been increasingly studied as exercise has been popular for the improvement of physical performance and rehabilitation of lumbar spine. A variety of exercises have been used to reduce back pain or spinal degeneration. However, there are no studies to determine effects of exercise on lumbar spine kinematics, including lumbar-pelvic coordination and instantaneous axis of rotation. The current study aimed to examine these lumbar spine kinematical changes due to exercise and therapy. We hypothesized that exercise and therapy will affect the changes of lumbar spine kinematics.
Lumbar-Pelvic motions were recorded from 86 healthy subjects while performing lifting and lowering tasks of 10% and 25% of body weight. The influence of exercise was quantified from coefficients of curve-fitting for pelvic and lumbar angles. There was a significant difference (p<0.05) for the range of lumbar motion (distribution, D) between the control group and the cardiovascular exercise group after 12-week program. However, there was no significance for lumbar-pelvic coordination, C.
A second study was performed to investigate the changes of instantaneous axis of rotation (IAR) at which trunk angle reached 25º. Results indicated that a superior-inferior location of IAR was significantly (p<0.05) modified by the cardiovascular exercise after 12 weeks, but there was no significant effectiveness of the physical therapy exercise.
Finding of lumbar spine kinematics during lifting and lowering a weight which are the most popular manual handling activities may provide great understanding of the exercise effectiveness. Future studies are recommended to assess whether the changes of lumbar spine kinematics lead to the decrease instances of lumbar spine injuries or low back pain. / Master of Science
|
Page generated in 0.033 seconds