3,181 research outputs found
Development of a computer model to predict platform station keeping requirements in the Gulf of Mexico using remote sensing data
Offshore operations such as oil drilling and radar monitoring require semisubmersible platforms to remain stationary at specific locations in the Gulf of Mexico. Ocean currents, wind, and waves in the Gulf of Mexico tend to move platforms away from their desired locations. A computer model was created to predict the station keeping requirements of a platform. The computer simulation uses remote sensing data from satellites and buoys as input. A background of the project, alternate approaches to the project, and the details of the simulation are presented
Statistical Mechanics of 2+1 Gravity From Riemann Zeta Function and Alexander Polynomial:Exact Results
In the recent publication (Journal of Geometry and Physics,33(2000)23-102) we
demonstrated that dynamics of 2+1 gravity can be described in terms of train
tracks. Train tracks were introduced by Thurston in connection with description
of dynamics of surface automorphisms. In this work we provide an example of
utilization of general formalism developed earlier. The complete exact solution
of the model problem describing equilibrium dynamics of train tracks on the
punctured torus is obtained. Being guided by similarities between the dynamics
of 2d liquid crystals and 2+1 gravity the partition function for gravity is
mapped into that for the Farey spin chain. The Farey spin chain partition
function, fortunately, is known exactly and has been thoroughly investigated
recently. Accordingly, the transition between the pseudo-Anosov and the
periodic dynamic regime (in Thurston's terminology) in the case of gravity is
being reinterpreted in terms of phase transitions in the Farey spin chain whose
partition function is just a ratio of two Riemann zeta functions. The mapping
into the spin chain is facilitated by recognition of a special role of the
Alexander polynomial for knots/links in study of dynamics of self
homeomorphisms of surfaces. At the end of paper, using some facts from the
theory of arithmetic hyperbolic 3-manifolds (initiated by Bianchi in 1892), we
develop systematic extension of the obtained results to noncompact Riemannian
surfaces of higher genus. Some of the obtained results are also useful for 3+1
gravity. In particular, using the theorem of Margulis, we provide new reasons
for the black hole existence in the Universe: black holes make our Universe
arithmetic. That is the discrete Lie groups of motion are arithmetic.Comment: 69 pages,11 figures. Journal of Geometry and Physics (in press
Leggett's bound for amorphous solids
We investigate the constraints on the superfluid fraction of an amorphous
solid following from an upper bound derived by Leggett. In order to accomplish
this, we use as input density profiles generated for amorphous solids in a
variety of different manners including by investigating Gaussian fluctuations
around classical results. These rough estimates suggest that, at least at the
level of the upper bound, there is not much difference in terms of
superfluidity between a glass and a crystal characterized by the same Lindemann
ratio. Moreover, we perform Path Integral Monte Carlo simulations of
distinguishable Helium 4 rapidly quenched from the liquid phase to very lower
temperature, at the density of the freezing transition. We find that the system
crystallizes very quickly, without any sign of intermediate glassiness. Overall
our results suggest that the experimental observations of large superfluid
fractions in Helium 4 after a rapid quench correspond to samples evolving far
from equilibrium, instead of being in a stable glass phase. Other scenarios and
comparisons to other results on the super-glass phase are also discussed.Comment: 11 pages, 5 figure
Coping with Change
The only constant in life is change. In this interactive program, Winthrop staff will explore their feelings, thoughts and actions as they relate to change. Strategies for coping with change will be discussed to ensure participants build personal resiliency to help cope with the uncertainties of life. The workshop offers an opportunity to: Identify normal responses to change Utilize skills and strategies to continue to grow and develop during periods of transition Learn the role resiliency plays in coping with change and Build personal resiliency skills for work and our personal live
Identifying bearded and ringed seal diet - a comparison of stomach contents, stable isotopes, fatty acids, and fecal dna
Thesis (M.S.) University of Alaska Fairbanks, 2014Stomach contents, stable isotopes, fatty acids, and more recently fecal DNA are commonly used to infer the diet of marine mammals. However, how complementary or contradictory these methods are, especially when considering individual diet variability, remains poorly understood. This study assessed the differences in the dietary information resulting from stomach contents, stable isotopes, and fatty acids for adult bearded seals (Erignathus barbatus), and fishes identified from stomach contents and fecal DNA for bearded and ringed seals (Pusa hispida), harvested in Alaska for subsistence use. Stomach contents and fecal DNA provided information on recently consumed prey. In contrast, stable carbon and nitrogen isotopes of muscle and fatty acid profiles of blubber provided information on prey consumed and integrated over a longer time frame, but taxonomic resolution of prey was low. Overall, stomach contents provided the most dietary data, while fecal DNA delivered the least. Using denaturing gradient gel electrophoresis (DGGE) of 16S gene fragments, only 40% of the fecal samples (12 bearded and one ringed seal) produced detectable DNA suitable for reference gene amplification. Only three fish species could be positively identified in the diet of seals (Arctic cod, Boreogadus saida; shorthorn sculpin, Myoxocephalus scorpius; and an unknown snailfish species, Liparidae) when using fecal DNA. In a dietary comparison, and despite differences in dietary time frames, the relative occurrence (RO) of prey from stomach contents and the mean proportions of prey source groups from a Bayesian stable isotope mixing model (SIAR) were similar. The proportions of indicator fatty acids from full-thickness blubber, such as 16:4n-1, 20:5n-3, 20:4n-6, 20:1n-9, 22:1n-11, and the presence of non-methylene-interrupted fatty acids were similar to other fatty acid studies of bearded seals in Alaska, and suggest a benthic diet. Overall, the methods yielded different, but not necessarily contradictory results.Chapter 1: General Introduction -- Chapter 2: Identifying bearded seal diet: a comparison of individual seals using stomach contents, stable isotopes, and fatty acids -- Chapter 3: Fish prey in bearded and ringed seal diet: a comparison of stomach contents and fecal DNA -- Chapter 4: General Conclusion
A comparison of personal-business knowledges and understandings of tenth-grade vocational and non-vocational students /
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