Data-driven optimal filtering for phase and frequency of noisy oscillations: Application to vortex flow metering

A method for measuring the phase of oscillations from noisy time series is proposed. To obtain the phase, the signal is filtered in such a way that the filter output has minimal relative variation in the amplitude over all filters with complex-valued impulse response. The argument of the filter output yields the phase. Implementation of the algorithm and interpretation of the result are discussed. We argue that the phase obtained by the proposed method has a low susceptibility to measurement noise and a low rate of artificial phase slips. The method is applied for the detection and classification of mode locking in vortex flow meters. A measure for the strength of mode locking is proposed.

Change in the use of and attitude to peak flow measurement among general practitioners in Northern Ireland between 1989 and 1994

In 1994 we repeated a study first performed in 1989 to assess the change in general practitioners' use of and attitudes to peak flow measurement. Of 232 general practitioners surveyed, 199 (86%) and 192 (83%) responded in 1989 and 1994 respectively. The percentage who reported having patients using domiciliary peak flow monitoring rose form 58.3 (95% confidence limits 51.4 to 65.2)% to 97.9 (95.9 to 99.9)%. The percentage who reported 'usually' using peak flow measurements for the diagnosis and management of asthma rose from 81.9 (76.5 to 87.3)% to 93.2 (89.6 to 96.8)% and from 83.3 (78.1 to 88.5)% to 95.8 (92.9 to 98.7)% respectively. An unchanged proportion took peak flow meters on house calls. General practitioners have become more aware of the potential of peak flow measurements but are still unlikely to have a meter available to assess patients seen at home. They are therefore likely to be ill-equipped to manage acute exacerbations of asthma in this setting.

Phase synchronization from noisy univariate signals

We present methods for detecting phase synchronization of two unidirectionally coupled, self-sustained noisy oscillators from a signal of the driven oscillator alone. One method detects soft phase locking; another hard phase locking. Both are applied to the problem of detecting phase synchronization in von Karman vortex flow meters.

Design of hydraulic structures considering different sheetpile configurations and flow through canal banks

This research investigated seepage under hydraulic structures considering flow through the banks of the canal. A computer model, utilizing the finite element method, was used. Different configurations of sheetpile driven under the floor of the structure were studied. Results showed that the transverse extension of sheetpile, driven at the middle of the floor, into the banks of the canal had very little effect on seepage losses, uplift force, and on the exit gradient at the downstream end of the floor. Likewise, confining the downstream floor with sheetpile from three sides was not found effective. When the downstream floor was confined with sheetpile from all sides, this has significantly reduced the exit gradient. Furthermore, all the different configurations of the sheetpile had insignificant effect on seepage losses. The most effective configuration of the sheetpile was the case when two rows of sheetpiles were driven at the middle and at the downstream end of the floor, with the latter sheetpile extended few meters into the banks of the canal. This case has significantly reduced the exit gradient and caused only slight increase in the uplift force when compared to other sheetpile configurations. The present study suggests that two-dimensional analysis of seepage problems underestimates the exit gradient and uplift force on hydraulic structures.

Hydrobiogeochemical Interactions along “Flow Tubes” Controls: Watershed Scale Contaminant Flow and Transformation at the Oak Ridge IFRC

Geochemical,spectrographic, microbiological and hydrogeologic studies at the ORIFRC site indicate that groundwater transport in structured media may behave as a system of parallel flow tubes. These tubes are preferred flowpaths that enable contaminant transport parallel to bedding planes (strike) over distances of 1000s of meters. A significant flux of groundwater is focused within an interval defined by the interface between the competent bedrock and overlying highly-weathered saprolite, commonly referred to as the"transition zone." Characteristics of this transition zone are dense fractures and the relative absence of weathering products (e.g. clays)results in a significantly higher permeability compared to both the overlying clay-saprolite and underlying bedrock. Several stratabound low seismic velocity zones located below the transition zone were identified during geophysics studies and were also determined to be fractured high permeability preferred contaminant transport pathways during subsequent drilling activities. XANES analysis of precipitates collected from these deeper flow zones indicate 95% or more of the U deposited is U(VI). Linear combination fitting of the EXAFS data shows that precipitates are ~51±5% U(VI)-carbonate-like phase (e.g., liebigite) and ~49±5% U(VI) associated with an iron oxide phase; inclusion of a third component in the fit suggests that up to 15% of the U(VI) may be associated with a phosphate phase or OH- phase (e.g.,schoepite). Although precipitates with similar U(VI)-carbonate and/or phosphate associations were identified in the transition zone pathways,there were also U(VI) complexes adsorbed to mineral surfaces that would tend to be more readily mobilized. Groundwater in the different flow tubes has been determined to consist of different water quality types that vary with the solid phase encountered (e.g., clays, carbonates, clastics) as contaminants migrate along the flow paths. This lateral and vertical variability in geochemistry, particularly pH, has a significant impact on microbiological community composition and activity. Ribosomal RNA gene analyses coupled with physiological and genomic analyses suggest that bacteria from the genus Rhodanobacter(a diverse population of denitrifiers that are moderately acid tolerant) have a high relative abundance in the acidic source zone at the ORIFRC site.Watershed-scale analysis across different flow paths/tubes revealed strong negative correlation between pH and the absolute and relative abundance of Rhodanobacter. Recent studies also confirmed that the ORIFRC site hosts a diverse fungal community, with significant differences observed between acidic (pH <5) and circumneutral (>5) wells. The lack of nitrous oxide reduction capability in fungi, and the detection of denitrification potential in slurry microcosms suggest that fungi may have aheretofore under appreciated role in biogeochemical transformations, with implications forsite remediation and greenhouse gas emissions. Further research is needed to determine if these organisms can influence U(VI) mobility either directly through immobilization or indirectly through the depletion of nitrate.In conclusion, additional studies are required to quantify the processes (e.g., solid phase reactions, recharge, diffusion, microbial interactions) that are occurring along the groundwater flow tubes identified at the ORIFRC so predictive models can be parameterized and used to assess long-term contaminant fate and transport and remedial options.