301 research outputs found
Asymptotics of the occupancy scheme in a random environment and its applications to tries
Get PDFConsider m copies of an irreducible, aperiodic Markov chain Y taking values in a finite state space. The asymptotics as m tends to infinity, of the first time from which on the trajectories of the m copies differ, have been studied by Szpankowski (1991) in the setting of tries. We use a different approach and model the m trajectories by a variant of the occupancy scheme, where we consider a nested sequence of boxes. This approach will enable us to extend the result to the case when the transition probabilities are random. We moreover use the same techniques to study the asymptotics as m tends to infinity of the time up to which we have observed all the possible trajectories of Y in random and nonrandom scener
Resume of Joost A. Businger, 1980
Get PDFNaval Postgraduate School Faculty ResumeIn 1980 he joined the faculty of the Department of Meteorology at the Naval Postgraduate School as the occupant of the George J. Haltiner Research Chair of Meteorology for a period of nine months. His research interests are in turbulence, planetary boundary layers and air-sea interaction
A Businger Mechanism for Intermittent Bursting in the Stable Boundary Layer
No full textHigh-resolution large-eddy simulations of the Antarctic very stable boundary layer reveal a mechanism for systematic and periodic intermittent bursting. A nonbursting state with a boundary layer height of just 3 m is alternated by a bursting state with a height of ≈5 m. The bursts result from unstable wave growth triggered by a shear-generated Kelvin–Helmholtz instability, as confirmed by linear stability analysis. The shear at the top of the boundary layer is built up by two processes. The upper, quasi-laminar layer accelerates due to the combined effect of the pressure force and rotation by the Coriolis force, while the lower layer decelerates by turbulent friction. During the burst, this shear is eroded and the initial cause of the instability is removed. Subsequently, the interfacial shear builds up again, causing the entire sequence to repeat itself with a time scale of ≈10 min. Despite the clear intermittent bursting, the overall change of the mean wind profile is remarkably small during the cycle. This enables such a fast erosion and recovery of the shear. This mechanism for cyclic bursting is remarkably similar to the mechanism hypothesized by Businger in 1973, with one key difference. Whereas Businger proposes that the flow acceleration in the upper layer results from downward turbulent transfer of high-momentum flow, the current results indicate no turbulent activity in the upper layer, hence requiring another source of momentum. Finally, it would be interesting to construct a climatology of shear-generated intermittency in relation to large-scale conditions to assess the generality of this Businger mechanism.Atmospheric Remote Sensin
Interpolation between Businger-Dyer formulae and free convection forms: A revised approach
No full textIn this study, profile functions for flux calculations during unstable conditions are proposed and examined. These functions are based on a direct interpolation for the dimensionless wind speed and temperature gradients between the standard Businger-Dyer formulae, φKu (ζ) = (1 - γuζ)-1/4, φKt(ζ) = (1 - γt ζ)-1/2, and free conviction forms, φCu,,t (ζ) = (1 - αCu,,tζ-1/3, ζ being the Monin-Obukhov stability parameter. A previously presented interpolation between the corresponding profile relationships, in attempting to provide a general relationship for the whole unstable regime, leads to serious restrictions for the values of αCu,,t in the free convection forms. These restrictions rendered available experimental data almost inapplicable, since the behaviour of the formulae in the near-neutral range controls the values of those parameters. The proposed interpolation provides functions that, firstly, fit the standard Businger-Dyer forms for near-neutral conditions and, secondly, satisfy the asymptotic behaviour as ζ → -∞, permitting wider ranges of possible αCu,,t values. This step is very important, taking into account the large spread of the experimental data. Thus, as further and more accurate observations at strong instability become available, this approach could prove very efficient in fitting these data while retaining correct near-neutral behaviour. © Springer 2005
Interpolation between Businger-Dyer formulae and free convection forms: A revised approach
No full textIn this study, profile functions for flux calculations during unstable conditions are proposed and examined. These functions are based on a direct interpolation for the dimensionless wind speed and temperature gradients between the standard Businger-Dyer formulae, φKu (ζ) = (1 - γuζ)-1/4, φKt(ζ) = (1 - γt ζ)-1/2, and free conviction forms, φCu,,t (ζ) = (1 - αCu,,tζ-1/3, ζ being the Monin-Obukhov stability parameter. A previously presented interpolation between the corresponding profile relationships, in attempting to provide a general relationship for the whole unstable regime, leads to serious restrictions for the values of αCu,,t in the free convection forms. These restrictions rendered available experimental data almost inapplicable, since the behaviour of the formulae in the near-neutral range controls the values of those parameters. The proposed interpolation provides functions that, firstly, fit the standard Businger-Dyer forms for near-neutral conditions and, secondly, satisfy the asymptotic behaviour as ζ → -∞, permitting wider ranges of possible αCu,,t values. This step is very important, taking into account the large spread of the experimental data. Thus, as further and more accurate observations at strong instability become available, this approach could prove very efficient in fitting these data while retaining correct near-neutral behaviour. © Springer 2005
Risikoeinschätzungsinstrument ISAR für geriatrische Personen ab 65 Jahren auf dem Notfall. Eine vergleichende Pilotstudie
No full textPapers 1, 2, 3, and 4 in Meteorological Studies at Plateau Station, Antarctica, Antarctic Research Series Volume 25.
No full text"Micrometeorological System: Installation, Performance, and Problems" by Paul C. Dalrymple and Leander A. Stroschein."A Year of Snow Accumulation at Plateau Station" by Uwe Radok and Robert C. Lile."Thermal Properties and Heat Transfer Processes of Low-Temperature Snow" and "Radiative Heat Transfer Processes in Snow and Ice" by Peter Schwerdtfeger and Gunter Weller
Arguments for and against a career in surgery: a qualitative analysis
No full textTo evaluate arguments given by board-certified surgeons in Switzerland for and against a career in surgery
Interest in a national research network in surgery in Switzerland
No full textNetworks are known to improve performance and create synergies. A research network can provide a significant advantage for all parties involved in research in surgery by systematically tracking the outcome of a huge number of patients over a long period of time. The aim of the present study was to investigate the experiences of surgeons with respect to research activities, to evaluate the opinions of surgeons with regard to the development of a national network for research in the field of surgery in Switzerland and to obtain data on how such a network should be designed
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