Heuristic explanation of journal bearing instability

A fluid-filled journal bearing is viewed as a powerful pump circulating fluid around the annular space between the journal and the bearing. A small whirling motion of the journal generates a wave of thickness variation progressing around the channel. The hypothesis that the fluid flow drives the whirl whenever the mean of the pumped fluid velocity is greater than the peripheral speed of the thickness variation wave is discussed and compared with other simple explanations of journal bearing instability. It is shown that for non-cavitation long bearings the hypothesis predicts instability onset correctly for unloaded bearings but gradually overpredicts the onset speed as the load is increased

Physical explanations of the destabilizing effect of damping in rotating parts

The destabilizing effect of rotating damping was investigated. When the rotation was faster than the whirl, rotating damping drags the orbiting particle forward. When stationary damping was also present, the stability borderline was readily determined by balancing the backward and forward drags. A key notion was that a forward whirl at rate omega a sub n with respect to stationary axes appears to be a backward whirl at rate Omega - omega sub n with respect to a system rotating supercritically at rate Omega. The growth rate of unstable whirls (or the decay rate of stable whirls was readily estimated by a simple energy balance

ON SCALING LAWS FOR MATERIAL DAMPING

Scaling laws for dampin

Frontal Injuries of the Skull

Results of injuries to the frontal parts of the skull are often serious but treatable by prompt surgery. Various types of fractures are common. Most dangerous is the possibility of infection in the interior cavities of the skull. X-ray study of such injuries is practically mandatory. Failure to give prompt and proper treatment often results in serious complications later. Any injury to the frontal parts of the skull should be viewed by attorneys as serious, with strong probability of future complications except perhaps when prompt medical attention of highly modern character has forestalled some of the possible complications

IDENTIFYING ENVIRONMENTAL FACTORS INFLUENCING GOLDEN EAGLE PRESENCE AND REPRODUCTIVE SUCCESS

Declining populations of plant and animal species is a major concern threatening global biodiversity. If we want to conserve threatened species, we must understand the requirements of the species. Recent data suggests Golden Eagle populations in the Western United States are declining. Future threats from expanded energy development, habitat loss and climate change are also a concern. Apparent declines and perceived threats have caused management agencies to classify the Golden Eagle as a species of concern requiring the creation of conservation plans. Yet, an effective conservation plan is dependent on information that is currently lacking. To address this lack of available information, I studied a population of breeding Golden Eagles in south-central Montana which has increased in the last 50 years. I was interested in determining which factors were responsible for the increase in the population and changes in measures of breeding performance. I used information from the current phase to identify which environmental factors are important for the eagles now and assessed whether the identified factors were responsible for the documented changes since the 1960’s. I found that Golden Eagles in the current phase were selecting areas for nesting territories based on prey habitat and terrain ruggedness. Within their territories, Golden Eagles selected areas conducive to uplift dependent on proximity to prey habitat, on a western aspect and closer to their nest. My results related to measures of breeding performance were unclear. I found prey habitat was likely not limiting the probability of territories being occupied between phases but instead, anthropogenic disturbance was likely limiting the historic population. My results suggest management plans should focus current protection on areas with prey habitat in close proximity to topography eagles can use to exploit uplift. To better understand the current population trends, I suggest expanding monitoring efforts to areas without a large degree of habitat loss in the last 50 years and to unprotected areas. Golden Eagle populations in these locations may be more indicative of the current status of the population range-wide

Star Jasmine : March

https://digitalcommons.library.umaine.edu/mmb-ps/2366/thumbnail.jp

Differential scattering with charge transfer to the 2s state of hydrogen from H/+/-He and H/+/-Ar collisions

Differential scattering with charge transfer to hydrogen 2s state from proton collisions with helium and argo

Sixty years of stochastic linearization technique

Stochastic linearization technique is a versatile method of solving nonlinear stochastic boundary value problems. It allows obtaining estimates of the response of the system when exact solution is unavailable; in contrast to the perturbation technique, its realization does not demand smallness of the parameter; on the other hand, unlike the Monte Carlo simulation it does not involve extensive computational cost. Although its accuracy may be not very high, this is remedied by the fact that the stochastic excitation itself need not be known quite precisely. Although it was advanced about six decades ago, during which several hundreds of papers were written, its foundations, as exposed in many monographs, appear to be still attracting investigators in stochastic dynamics. This study considers the methodological and pedagogical aspects of its exposition

Repeatability of brown adipose tissue measurements on FDG PET/CT following a simple cooling procedure for BAT activation

Brown Adipose Tissue (BAT) is present in a significant number of adult humans and can be activated by exposure to cold. Measurement of active BAT presence, activity, and volume are desirable for determining the efficacy of potential treatments intended to activate BAT. The repeatability of 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) measurements of BAT presence, activity, and volume under controlled conditions has not been extensively studied. Eleven female volunteers underwent double baseline FDG PET imaging performed following a simple, regional cold intervention intended to activate brown fat. The cold intervention involved the lightly-clothed participants intermittently placing their feet on a block of ice while sitting in a cooled room. A repeat study was performed under the same conditions within a target of two weeks. FDG scans were obtained and maximum standardized uptake value adjusted for lean body mass (SULmax), CT Hounsfield units (HU), BAT metabolic volume (BMV), and total BAT glycolysis (TBG) were determined according to the Brown Adipose Reporting Criteria in Imaging STudies (BARCIST) 1.0. A Lin's concordance correlation (CCC) of 0.80 was found for BMV between test and retest imaging. Intersession BAT SULmax was significantly correlated (r = 0.54; p < 0.05). The session #1 mean SULmax of 4.92 ± 4.49 g/mL was not significantly different from that of session #2 with a mean SULmax of 7.19 ± 7.34 g/mL (p = 0.16). BAT SULmax was highly correlated with BMV in test and retest studies (r ≥ 0.96, p < 0.001). Using a simplified ice-block cooling method, BAT was activated in the majority (9/11) of a group of young, lean female participants. Quantitative assessments of BAT SUL and BMV were not substantially different between test and retest imaging, but individual BMV could vary considerably. Intrasession BMV and SULmax were strongly correlated. The variability in estimates of BAT activity and volume on test-retest with FDG should inform sample size choice in studies quantifying BAT physiology and support the dynamic metabolic characteristics of this tissue. A more sophisticated cooling method potentially may reduce variations in test-retest BAT studies