7,182 research outputs found
An analytical model for bore-driven run-up
No full textWe use a hodograph transformation and a boundary integral method to derive a new analytical solution to the shallow-water equations describing bore-generated run-up on a plane beach. This analytical solution differs from the classical Shen-Meyer runup solution in giving significantly deeper and less asymmetric swash flows, and also by predicting the inception of a secondary bore in both the backwash and the uprush in long surf. We suggest that this solution provides a significantly improved model for flows including swash events and the run-up following breaking tsunamis
Vibro-Acoustic Characteristic of A Self Aligning Spherical Journal Bearing due to Eccentric Bore Fault
No full textSelf aligning spherical journal bearing is a type of plain bearings which has spherical surface contact. This type of bearing can accommodate a misalignment problem. The journal bearing faults degrade machine performance, decrease life time service and unexpected failure which are dangerous for safety issues. Surface vibration (SV), airborne sound (AS) and acoustic emission (AE) measurements are appropriate monitoring methods for early stage journal bearing fault in low, medium and high frequency.
This paper focuses on the performance comparison between SV, AS and AE measurements in the self aligning spherical journal bearing with normal and eccentric bore faults. The dynamics of the bearing is studied to gain the generation and characteristics of SV, AS and AE, which allow the extraction of useful information for diagnosis. The results of SV, AS and AE experiments especially for self-aligning spherical journal bearing due to eccentric bore fault indicate that the spectrum can detect significantly distinct between normal and faulty bearing. The statistic parameters show that RMS value and Peak value for fault bearing is higher than normal bearing. Spectrum of SV, AS and SE showed significant differences between normal bearing and eccentric bore bearing
Vibro-Acoustic Characteristic of A Self Aligning Spherical Journal Bearing due to Eccentric Bore Fault
No full textSelf aligning spherical journal bearing is a type of plain bearings which has spherical surface contact. This type of bearing can accommodate a misalignment problem. The journal bearing faults degrade machine performance, decrease life time service and unexpected failure which are dangerous for safety issues. Surface vibration (SV), airborne sound (AS) and acoustic emission (AE) measurements are appropriate monitoring methods for early stage journal bearing fault in low, medium and high frequency.
This paper focuses on the performance comparison between SV, AS and AE measurements in the self aligning spherical journal bearing with normal and eccentric bore faults. The dynamics of the bearing is studied to gain the generation and characteristics of SV, AS and AE, which allow the extraction of useful information for diagnosis. The results of SV, AS and AE experiments especially for self-aligning spherical journal bearing due to eccentric bore fault indicate that the spectrum can detect significantly distinct between normal and faulty bearing. The statistic parameters show that RMS value and Peak value for fault bearing is higher than normal bearing. Spectrum of SV, AS and SE showed significant differences between normal bearing and eccentric bore bearing
Bore
No full textC. MacPherson standing next to the pipe (right) for the artesian bore water supply to Marree. Taken from the top of the filtering tank.Blockley, John.Date:194
Infragravity waves and bore merging
No full textThe phenomenon of bore merging is investigated using two high-resolution laboratory experiments including bichromatic and irregular wave conditions. The locations at which waves start merging are identified and the hydrodynamic conditions in the vicinity of the merging points are examined. Bore merging takes place in the inner surf zone for all conditions considered. The infragravity- to short-wave height ratio is close to or larger than one at the merging point, indicating that bore merging occurs in a part of the surf zone that is already dominated by the infragravity waves. Our data analysis is supplemented by numerical simulations that confirms the importance of infragravity waves in the occurrence bore merging. Moreover, our simulations suggest that bore merging has a very limited effect on the infragravity wave field. This casts doubts on the importance of bore merging as an infragravity wave generation mechanism.Environmental Fluid Mechanic
Development of a large bore superconducting magnet with narrow liquid helium channels
No full textA large bore NbTi superconducting magnet is designed, manufactured and tested. The superconducting magnet has an inner diameter of 460 mm, outer diameter of 600 mm and height of 540 mm. The magnet is dry wound using rectangular and round superconducting wires with their dimensions of 1.3 times 2.0 mm and Oslash1.3 mm respectively. In order to improve helium cooling effect, narrow liquid helium channels are set between adjacent layers. The magnet can generate 4 T central magnetic field at the designed operating current of 305 A. The magnet has been tested in a compact cryostat. Experimental results show that the superconducting magnet reached the designed magnetic performance. Details of the magnet design, fabrication and test are described in this paper
Food for microorganisms: Position-specific 13 C labeling and 13 C-PLFA analysis reveals preferences for sorbed or necromass C
No full textAnalysis of Bore Characteristics Using KdV-Based Nonlinear Fourier Transform
No full textBores propagating in shallow water transform into undular bores and, finally, into trains of solitons. The observed number and height of these undulations, and later discrete solitons, is strongly dependent on the propagation length of the bore. Empirical results show that the final height of the leading soliton in the far-field is twice the initial mean bore height. The complete disintegration of the initial bore into a train of solitons requires very long propagation lengths, but unfortunately these required distances are usually not available in experimental tests or nature. Therefore, the analysis of the bore decomposition for experimental data into solitons is difficult and requires further approaches. Previous studies have shown that by application of the nonlinear Fourier transform based on the Korteweg–de Vries equation (KdV-NFT) to bores and long-period waves propagating in constant depth, the number and height of all solitons can be reliably predicted already based on the initial bore-shaped free surface.Against this background, this study presents the systematic analysis of the leading-soliton amplitudes for non-breaking and breaking bores with different strengths in different water depths in order to validate the KdV-NFT results for non-breaking bores, and to show the limitations of wave breaking on the spectral results. The analytical results are compared with data from experimental tests, numerical simulations and other approaches from literature.Accepted Author ManuscriptTeam Sander Wahl
Microbial Metabolism in Soil at Subzero Temperatures: Adaptation Mechanisms Revealed by Position-Specific 13C Labeling
No full text© 2017 Bore, Apostel, Halicki, Kuzyakov and Dippold.Although biogeochemical models designed to simulate carbon (C) and nitrogen (N) dynamics in high-latitude ecosystems incorporate extracellular parameters, molecular and biochemical adaptations of microorganisms to freezing remain unclear. This knowledge gap hampers estimations of the C balance and ecosystem feedback in high-latitude regions. To analyze microbial metabolism at subzero temperatures, soils were incubated with isotopomers of position-specifically 13C-labeled glucose at three temperatures: +5 (control), -5, and -20°C. 13C was quantified in CO2, bulk soil, microbial biomass, and dissolved organic carbon (DOC) after 1, 3, and 10 days and also after 30 days for samples at -20°C. Compared to +5°C, CO2 decreased 3- and 10-fold at -5 and -20°C, respectively. High 13C recovery in CO2 from the C-1 position indicates dominance of the pentose phosphate pathway at +5°C. In contrast, increased oxidation of the C-4 position at subzero temperatures implies a switch to glycolysis. A threefold higher 13C recovery in microbial biomass at -5 than +5°C points to synthesis of intracellular compounds such as glycerol and ethanol in response to freezing. Less than 0.4% of 13C was recovered in DOC after 1 day, demonstrating complete glucose uptake by microorganisms even at -20°C. Consequently, we attribute the fivefold higher extracellular 13C in soil than in microbial biomass to secreted antifreeze compounds. This suggests that with decreasing temperature, intracellular antifreeze protection is complemented by extracellular mechanisms to avoid cellular damage by crystallizing water. The knowledge of sustained metabolism at subzero temperatures will not only be useful for modeling global C dynamics in ecosystems with periodically or permanently frozen soils, but will also be important in understanding and controlling the adaptive mechanisms of food spoilage organisms
Overtopping a truncated planar beach
No full textRun-up on a truncated impermeable beach is analysed theoretically and experimentally to find the volume of fluid, associated with a single wave event, that flows over the end of the beach. The theoretical calculations investigate the motion using the shallow-water equations and the fluid is allowed to flow freely over the end of the beach. Two models of wave events are considered: dam-break initial conditions, in which fluid collapses from rest to run-up and overtop the beach, and a waveform that models swash associated with the collapse of a long solitary bore. The calculations are made using quasi-analytical techniques, following the hodograph transformation of the governing equations. They yield predictions for the volume of fluid per unit width that overtops the beach, primarily as a function of the dimensionless length of the beach. These predictions are often far in excess of previous theoretical calculations. New experimental results are also reported in which the overtopping volumes due to flows initiated from dam-break conditions are studied for a range of reservoir lengths and heights and for a range of lengths and inclinations of the beach. Without the need for any empirically fitted parameters, good agreement is found between the experimental measurements and the theoretical predictions in regimes for which the effects of drag are negligible
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