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Sample records for 4q3 low-flow frequency

  1. Analysis of the magnitude and frequency of the 4-day annual low flow and regression equations for estimating the 4-day, 3-year low-flow frequency at ungaged sites on unregulated streams in New Mexico

    USGS Publications Warehouse

    Waltemeyer, Scott D.

    2002-01-01

    Two regression equations were developed for estimating the 4- day, 3-year (4Q3) low-flow frequency at ungaged sites on unregulated streams in New Mexico. The first, a statewide equation for estimating the 4Q3 low-flow frequency from drainage area and average basin mean winter precipitation, was developed from the data for 50 streamflow-gaging stations that had non-zero 4Q3 low-flow frequency. The 4Q3 low-flow frequency for the 50 gaging stations ranged from 0.08 to 18.7 cubic feet per second. For this statewide equation, the average standard error of estimate was 126 percent and the coefficient of determination was 0.48. The second, an equation for estimating the 4Q3 low-flow frequency in mountainous regions from drainage area, average basin mean winter precipitation, and average basin slope, was developed from the data for 40 gaging stations located above 7,500 feet in elevation. For this regression equation, the average standard error of estimate was 94 percent and the coefficient of determination was 0.66. A U.S. Geological Survey computer-program interface for a geographical information system (GIS), called the GIS Weasel, was used to determine basin and climatic characteristics for 84 gaging stations that were not affected by regulation. Mean monthly precipitation estimates from 1961 to 1990 were used in the GIS Weasel to compute the climatic characteristics of average basin winter precipitation and annual mean precipitation. The U.S. Geological Survey National Elevation Dataset, which currently consists of the 7.5-minute, 30-meter digital elevation model for each State, was used in the GIS Weasel to compute the basin characteristics of drainage area, average basin slope, average basin elevation, and average basin aspect. Basin and climatic characteristics that were statistically significant in the regression equation with the 4Q3 low-flow frequency were drainage area, which ranged from 1.62 to 5,900 square miles; average basin mean winter precipitation, which

  2. Climate Informed Low Flow Frequency Analysis Using Nonstationary Modeling

    NASA Astrophysics Data System (ADS)

    Liu, D.; Guo, S.; Lian, Y.

    2014-12-01

    Stationarity is often assumed for frequency analysis of low flows in water resources management and planning. However, many studies have shown that flow characteristics, particularly the frequency spectrum of extreme hydrologic events,were modified by climate change and human activities and the conventional frequency analysis without considering the non-stationary characteristics may lead to costly design. The analysis presented in this paper was based on the more than 100 years of daily flow data from the Yichang gaging station 44 kilometers downstream of the Three Gorges Dam. The Mann-Kendall trend test under the scaling hypothesis showed that the annual low flows had significant monotonic trend, whereas an abrupt change point was identified in 1936 by the Pettitt test. The climate informed low flow frequency analysis and the divided and combined method are employed to account for the impacts from related climate variables and the nonstationarities in annual low flows. Without prior knowledge of the probability density function for the gaging station, six distribution functions including the Generalized Extreme Values (GEV), Pearson Type III, Gumbel, Gamma, Lognormal, and Weibull distributions have been tested to find the best fit, in which the local likelihood method is used to estimate the parameters. Analyses show that GEV had the best fit for the observed low flows. This study has also shown that the climate informed low flow frequency analysis is able to exploit the link between climate indices and low flows, which would account for the dynamic feature for reservoir management and provide more accurate and reliable designs for infrastructure and water supply.

  3. Low-flow frequency analyses for streams in west-central Florida

    USGS Publications Warehouse

    Hammett, K.M.

    1985-01-01

    The log-Pearson type III distribution was used for defining low-flow frequency at 116 continuous-record streamflow stations in west-central Florida. Frequency distributions were calculated for 1, 3, 7, 14, 30, 60, 90, 120, and 183 consecutive-day periods for recurrence intervals of 2, 5, 10, and 20 years. Discharge measurements at more than 100 low-flow partial-record stations and miscellaneous discharge-measurement stations were correlated with concurrent daily mean discharge at continuous-record stations. Estimates of the 7-day, 2-year; 7-day, 10-year; 30-day, 2-year; and 30-day, 10-year discharges were made for most of the low-flow partial-record and miscellaneous discharge-measurement stations based on those correlations. Multiple linear-regression analysis was used in an attempt to mathematically relate low-flow frequency data to basin characteristics. The resulting equations showed an apparent bias and were considered unsatisfactory for use in estimating low-flow characteristics. Maps of the 7-day, 10-year and 30-day, 10-year low flows are presented. Techniques that can be used to estimate low-flow characteristics at an ungaged site are also provided. (USGS)

  4. ESTIMATING LOW-FLOW FREQUENCIES OF UNGAGED STREAMS IN NEW ENGLAND.

    USGS Publications Warehouse

    Wandle, S. William, Jr.

    1987-01-01

    Equations to estimate low flows were developed using multiple-regression analysis with a sample of 48 river basins, which were selected from the U. S. Geological Survey's network of gaged river basins in Massachusetts, New Hampshire, Rhode Island, Vermont, and southwestern Maine. Low-flow characteristics are represented by the 7Q2 and 7Q10 (the annual minimum 7-day mean low flow at the 2- and 10-year recurrence intervals). These statistics for each of the 48 basins were determined from a low-flow frequency analysis of streamflow records for 1942-71, or from a graphical or mathematical relationship if the record did not cover this 30-year period. Estimators for the mean and variance of the 7-day low flows at the index and short-term sites were used for two stations where discharge measurements of base flow were available and for two sites where the graphical technique was unsatisfactory.

  5. Methods used to compute low-flow frequency characteristics for continuous-record streamflow stations in Minnesota, 2006

    USGS Publications Warehouse

    Winterstein, Thomas A.; Arntson, Allan D.; Mitton, Gregory B.

    2007-01-01

    The 1-, 7-, and 30-day low-flow series were determined for 120 continuous-record streamflow stations in Minnesota having at least 20 years of continuous record. The 2-, 5-, 10-, 50-, and 100-year statistics were determined for each series by fitting a log Pearson type III distribution to the data. The methods used to determine the low-flow statistics and to construct the plots of the low-flow frequency curves are described. The low-flow series and the low-flow statistics are presented in tables and graphs.

  6. Low-flow frequency curves for selected long-term stream gaging stations in eastern United States

    USGS Publications Warehouse

    Hardison, Clayton H.; Martin, Robert O.R.

    1963-01-01

    Curves showing the magnitude and frequency of annual low flow at 85 streamgaging stations located in 17 States east and 5 States west of the Mississippi River have been smoothed and adjusted to one of four long-term periods. They are presented to show the similarity and dissimilarity of curves even in the same State and to provide background information for studies of the statistical properties of low-flow frequency curves and for studies of the relation between hydrologic environment and low flow. The results are presented as greatly reduced graphs to facilitate comparison and are summarized in tables from which expanded graphs can be plotted.

  7. Estimating Flow-Duration and Low-Flow Frequency Statistics for Unregulated Streams in Oregon

    USGS Publications Warehouse

    Risley, John; Stonewall, Adam J.; Haluska, Tana

    2008-01-01

    Flow statistical datasets, basin-characteristic datasets, and regression equations were developed to provide decision makers with surface-water information needed for activities such as water-quality regulation, water-rights adjudication, biological habitat assessment, infrastructure design, and water-supply planning and management. The flow statistics, which included annual and monthly period of record flow durations (5th, 10th, 25th, 50th, and 95th percent exceedances) and annual and monthly 7-day, 10-year (7Q10) and 7-day, 2-year (7Q2) low flows, were computed at 466 streamflow-gaging stations at sites with unregulated flow conditions throughout Oregon and adjacent areas of neighboring States. Regression equations, created from the flow statistics and basin characteristics of the stations, can be used to estimate flow statistics at ungaged stream sites in Oregon. The study area was divided into 10 regression modeling regions based on ecological, topographic, geologic, hydrologic, and climatic criteria. In total, 910 annual and monthly regression equations were created to predict the 7 flow statistics in the 10 regions. Equations to predict the five flow-duration exceedance percentages and the two low-flow frequency statistics were created with Ordinary Least Squares and Generalized Least Squares regression, respectively. The standard errors of estimate of the equations created to predict the 5th and 95th percent exceedances had medians of 42.4 and 64.4 percent, respectively. The standard errors of prediction of the equations created to predict the 7Q2 and 7Q10 low-flow statistics had medians of 51.7 and 61.2 percent, respectively. Standard errors for regression equations for sites in western Oregon were smaller than those in eastern Oregon partly because of a greater density of available streamflow-gaging stations in western Oregon than eastern Oregon. High-flow regression equations (such as the 5th and 10th percent exceedances) also generally were more accurate

  8. Changes in low-flow frequency from 1976-2006 at selected streamgages in New York, excluding Long Island

    USGS Publications Warehouse

    Suro, Thomas P.; Gazoorian, Christopher L.

    2011-01-01

    At-site low-flow statistics were updated for eight streamgages in New York by using continuous daily streamflow data through 2006 for the future development of a statewide research study. Selection of the eight streamgages used in this study identified a major deficiency in the number of available unregulated long-term U.S. Geological Survey streamgages needed for the development of regional low-flow equations in New York. A limited analysis of the changes in land use for the contributing drainage areas for each streamgage, changes in precipitation, and trends in the annual 7-day minimum flow also are presented. The 7-day, 2-year low flow showed increases of 14 to 35 percent and the 7-day 10-year low flow showed zero to 19 percent increases at rural streamgages with unregulated streamflows when statistics were computed by using data from 1976 through 2006 and compared with published data in Bulletin 74. When the entire period of record was used to compute low flow frequencies, the 7-day, 2-year low flows increased from about 6 to 15 percent whereas the 7-day 10-year low flows showed zero to 5 percent increases. Streamgages affected by urbanization and regulation for water supply showed the most significant changes in the 7-day, 2-year and 10-year low-flow frequencies. These streamgages are included to help identify the effects of urbanization and regulation on streamflow at these locations. The 7-day 10-year low flow increased by 65 percent at the U.S. Geological Survey streamgage Hackensack River at West Nyack, N.Y., and increased 120 percent at the U.S. Geological Survey streamgage Neversink River at Godeffroy, N.Y., when statistics were computed by using data from 1976 through 2006 and compared with the statistics for the regulated period computed in Bulletin 74.

  9. Flow Durations, Low-Flow Frequencies, and Monthly Median Flows for Selected Streams in Connecticut through 2005

    USGS Publications Warehouse

    Ahearn, Elizabeth A.

    2008-01-01

    Flow durations, low-flow frequencies, and monthly median streamflows were computed for 91 continuous-record, streamflow-gaging stations in Connecticut with 10 or more years of record. Flow durations include the 99-, 98-, 97-, 95-, 90-, 85-, 80-, 75-, 70-, 60-, 50-, 40-, 30-, 25-, 20-, 10-, 5-, and 1-percent exceedances. Low-flow frequencies include the 7-day, 10-year (7Q10) low flow; 7-day, 2-year (7Q2) low flow; and 30-day, 2-year (30Q2) low flow. Streamflow estimates were computed for each station using data for the period of record through water year 2005. Estimates of low-flow statistics for 7 short-term (operated between 3 and 10 years) streamflow-gaging stations and 31 partial-record sites were computed. Low-flow estimates were made on the basis of the relation between base flows at a short-term station or partial-record site and concurrent daily mean streamflows at a nearby index station. The relation is defined by the Maintenance of Variance Extension, type 3 (MOVE.3) method. Several short-term stations and partial-record sites had poorly defined relations with nearby index stations; therefore, no low-flow statistics were derived for these sites. The estimated low-flow statistics for the short-term stations and partial-record sites include the 99-, 98-, 97-, 95-, 90-, and 85-percent flow durations; the 7-day, 10-year (7Q10) low flow; 7-day, 2-year (7Q2) low flow; and 30-day, 2-year (30Q2) low-flow frequencies; and the August median flow. Descriptive information on location and record length, measured basin characteristics, index stations correlated to the short-term station and partial-record sites, and estimated flow statistics are provided in this report for each station. Streamflow estimates from this study are stored on USGS's World Wide Web application 'StreamStats' (http://water.usgs.gov/osw/streamstats/connecticut.html).

  10. Estimating selected low-flow frequency statistics and harmonic-mean flows for ungaged, unregulated streams in Indiana

    USGS Publications Warehouse

    Martin, Gary R.; Fowler, Kathleen K.; Arihood, Leslie D.

    2016-01-01

    Information on low-flow characteristics of streams is essential for the management of water resources. This report provides equations for estimating the 1-, 7-, and 30-day mean low flows for a recurrence interval of 10 years and the harmonic-mean flow at ungaged, unregulated stream sites in Indiana. These equations were developed using the low-flow statistics and basin characteristics for 108 continuous-record streamgages in Indiana with at least 10 years of daily mean streamflow data through the 2011 climate year (April 1 through March 31). The equations were developed in cooperation with the Indiana Department of Environmental Management.Regression techniques were used to develop the equations for estimating low-flow frequency statistics and the harmonic-mean flows on the basis of drainage-basin characteristics. A geographic information system was used to measure basin characteristics for selected streamgages. A final set of 25 basin characteristics measured at all the streamgages were evaluated to choose the best predictors of the low-flow statistics.Logistic-regression equations applicable statewide are presented for estimating the probability that selected low-flow frequency statistics equal zero. These equations use the explanatory variables total drainage area, average transmissivity of the full thickness of the unconsolidated deposits within 1,000 feet of the stream network, and latitude of the basin outlet. The percentage of the streamgage low-flow statistics correctly classified as zero or nonzero using the logistic-regression equations ranged from 86.1 to 88.9 percent.Generalized-least-squares regression equations applicable statewide for estimating nonzero low-flow frequency statistics use total drainage area, the average hydraulic conductivity of the top 70 feet of unconsolidated deposits, the slope of the basin, and the index of permeability and thickness of the Quaternary surficial sediments as explanatory variables. The average standard error of

  11. Assessing the Vulnerability of Streams to Increased Frequency and Severity of Low Flows in the Southeastern United States

    NASA Astrophysics Data System (ADS)

    Konrad, C. P.

    2014-12-01

    A changing climate poses risks to the availability and quality of water resources. Among the risks, increased frequency and severity of low flow periods in streams would be significant for many in-stream and out-of-stream uses of water. While down-scaled climate projections serve as the basis for understanding impacts of climate change on hydrologic systems, a robust framework for risk assessment incorporates multiple dimensions of risks including the vulnerability of hydrologic systems to climate change impacts. Streamflow records from the southeastern US were examined to assess the vulnerability of streams to increased frequency and severity of low flows. Long-term (>50 years) records provide evidence of more frequent and severe low flows in more streams than would be expected from random chance. Trends in low flows appear to be a result of changes in the temporal distribution rather than the annual amount of preciptation and/or in evaporation. Base flow recession provides an indicator of a stream's vulnerability to such changes. Linkages between streamflow patterns across temporal scales can be used for understanding and asessing stream responses to the various possible expressions of a changing climate.

  12. Evaluation of a method of estimating low-flow frequencies from base-flow measurements at Indiana streams

    USGS Publications Warehouse

    Wilson, John Thomas

    2000-01-01

    A mathematical technique of estimating low-flow frequencies from base-flow measurements was evaluated by using data for streams in Indiana. Low-flow frequencies at low- flow partial-record stations were estimated by relating base-flow measurements to concurrent daily flows at nearby streamflow-gaging stations (index stations) for which low-flowfrequency curves had been developed. A network of long-term streamflow-gaging stations in Indiana provided a sample of sites with observed low-flow frequencies. Observed values of 7-day, 10-year low flow and 7-day, 2-year low flow were compared to predicted values to evaluate the accuracy of the method. Five test cases were used to evaluate the method under a variety of conditions in which the location of the index station and its drainage area varied relative to the partial-record station. A total of 141 pairs of streamflow-gaging stations were used in the five test cases. Four of the test cases used one index station, the fifth test case used two index stations. The number of base-flow measurements was varied for each test case to see if the accuracy of the method was affected by the number of measurements used. The most accurate and least variable results were produced when two index stations on the same stream or tributaries of the partial-record station were used. All but one value of the predicted 7-day, 10-year low flow were within 15 percent of the values observed for the long-term continuous record, and all of the predicted values of the 7-day, 2-year lowflow were within 15 percent of the observed values. This apparent accuracy, to some extent, may be a result of the small sample set of 15. Of the four test cases that used one index station, the most accurate and least variable results were produced in the test case where the index station and partial-record station were on the same stream or on streams tributary to each other and where the index station had a larger drainage area than the partial-record station. In

  13. Regional low-flow frequency analysis using single and ensemble artificial neural networks

    NASA Astrophysics Data System (ADS)

    Ouarda, T. B. M. J.; Shu, C.

    2009-11-01

    In this paper, artificial neural networks (ANNs) are introduced to obtain improved regional low-flow estimates at ungauged sites. A multilayer perceptron (MLP) network is used to identify the functional relationship between low-flow quantiles and the physiographic variables. Each ANN is trained using the Levenberg-Marquardt algorithm. To improve the generalization ability of a single ANN, several ANNs trained for the same task are used as an ensemble. The bootstrap aggregation (or bagging) approach is used to generate individual networks in the ensemble. The stacked generalization (or stacking) technique is adopted to combine the member networks of an ANN ensemble. The proposed approaches are applied to selected catchments in the province of Quebec, Canada, to obtain estimates for several representative low-flow quantiles of summer and winter seasons. The jackknife validation procedure is used to evaluate the performance of the proposed models. The ANN-based approaches are compared with the traditional parametric regression models. The results indicate that both the single and ensemble ANN models provide superior estimates than the traditional regression models. The ANN ensemble approaches provide better generalization ability than the single ANN models.

  14. Development of regression equations to estimate flow durations and low-flow-frequency statistics in New Hampshire streams

    USGS Publications Warehouse

    Flynn, Robert H.

    2003-01-01

    Regression equations and basin-characteristic digital datasets were developed to help water-resource managers estimate surface-water resources during periods of low flow in New Hampshire. The regression equations were developed to estimate statistics for the seasonal and annual low-flow-frequency and seasonal period-of-record and period-of-record flow durations. Because streamflow is maintained by ground-water discharge during periods of low flow, these equations also will aid in the assessment of ground-water availability. Ultimately, the equations and datasets developed herein can be combined with data on water withdrawals, discharges, and interbasin transfers in a geographic information system (GIS) to allow assessments of water use and water availability in any drainage basin in the State of New Hampshire. Regression equations developed in this study provide estimates of the seasonal (spring, summer, fall, and winter) and annual 7-day 2-year (7Q2) and 7-day 10-year (7Q10) low-flow-frequency values, as well as seasonal period-of-record and period-of-record flow durations (60-, 70-, 80-, 90-, 95-, and 98-percent exceedences) for ungaged reaches of unregulated New Hampshire streams. Regression equations were developed using seasonal and annual low-flow statistics from 58 to 60 continuous-record stream-gaging stations in New Hampshire and nearby areas in neighboring states, and measurements of various characteristics of the drainage basins that contribute flow to those stations. The estimating equations for the seasonal and annual 7Q2 and 7Q10 values were developed using generalized-least-squares (GLS) regression analyses. The GLS equations developed for these flow statistics gave average prediction errors that ranged from 11 to 61 percent. The estimating equations for flow-duration exceedence frequency values were developed using ordinary-least-squares (OLS) regression analysis. The OLS equations developed for these flow statistics gave average prediction errors

  15. Computed statistics at streamgages, and methods for estimating low-flow frequency statistics and development of regional regression equations for estimating low-flow frequency statistics at ungaged locations in Missouri

    USGS Publications Warehouse

    Southard, Rodney E.

    2013-01-01

    The weather and precipitation patterns in Missouri vary considerably from year to year. In 2008, the statewide average rainfall was 57.34 inches and in 2012, the statewide average rainfall was 30.64 inches. This variability in precipitation and resulting streamflow in Missouri underlies the necessity for water managers and users to have reliable streamflow statistics and a means to compute select statistics at ungaged locations for a better understanding of water availability. Knowledge of surface-water availability is dependent on the streamflow data that have been collected and analyzed by the U.S. Geological Survey for more than 100 years at approximately 350 streamgages throughout Missouri. The U.S. Geological Survey, in cooperation with the Missouri Department of Natural Resources, computed streamflow statistics at streamgages through the 2010 water year, defined periods of drought and defined methods to estimate streamflow statistics at ungaged locations, and developed regional regression equations to compute selected streamflow statistics at ungaged locations. Streamflow statistics and flow durations were computed for 532 streamgages in Missouri and in neighboring States of Missouri. For streamgages with more than 10 years of record, Kendall’s tau was computed to evaluate for trends in streamflow data. If trends were detected, the variable length method was used to define the period of no trend. Water years were removed from the dataset from the beginning of the record for a streamgage until no trend was detected. Low-flow frequency statistics were then computed for the entire period of record and for the period of no trend if 10 or more years of record were available for each analysis. Three methods are presented for computing selected streamflow statistics at ungaged locations. The first method uses power curve equations developed for 28 selected streams in Missouri and neighboring States that have multiple streamgages on the same streams. Statistical

  16. Low-flow frequency and flow duration of selected South Carolina streams in the Pee Dee River basin through March 2007

    USGS Publications Warehouse

    Feaster, Toby D.; Guimaraes, Wladmir B.

    2009-01-01

    Part of the mission of the South Carolina Department of Health and Environmental Control and the South Carolina Department of Natural Resources is to protect and preserve South Carolina's water resources. Doing so requires an ongoing understanding of streamflow characteristics of the rivers and streams in South Carolina. A particular need is information concerning the low-flow characteristics of streams; this information is especially important for effectively managing the State's water resources during critical flow periods such as the severe drought that occurred between 1998 and 2002 and the most recent drought that occurred between 2006 and 2009. In 2008, the U.S. Geological Survey, in cooperation with the South Carolina Department of Health and Environmental Control, initiated a study to update low-flow statistics at continuous-record streamgaging stations operated by the U.S. Geological Survey in South Carolina. Under this agreement, the low-flow characteristics at continuous-record streamgaging stations will be updated in a systematic manner during the monitoring and assessment of the eight major basins in South Carolina as defined and grouped according to the South Carolina Department of Health and Environmental Control's Watershed Water Quality Management Strategy. Depending on the length of record available at the continuous-record streamgaging stations, low-flow frequency characteristics are estimated for annual minimum 1-, 3-, 7-, 14-, 30-, 60-, and 90-day average flows with recurrence intervals of 2, 5, 10, 20, 30, and 50 years. Low-flow statistics are presented for 18 streamgaging stations in the Pee Dee River basin. In addition, daily flow durations for the 5-, 10-, 25-, 50-, 75-, 90-, and 95-percent probability of exceedance also are presented for the stations. The low-flow characteristics were computed from records available through March 31, 2007. The last systematic update of low-flow characteristics in South Carolina occurred more than 20 years

  17. Low-flow characteristics of Alabama streams

    USGS Publications Warehouse

    Bingham, Roy H.

    1982-01-01

    A new procedure for estimating the 7-day, 2-year and the 7-day, 10-year low flow of ungaged Alabama streams is based on geology, drainage area, and mean annual precipitation. One equation for each of the two low-flow frequencies applies statewide to all natural flow streams; the equations do not apply to streams where flow is significantly altered by activities of man. The standard error of estimate of each equation based on map values is 40 percent for 7-day, 2-year low flow and 44 percent for 7-day, 10-year low flow. The rate of streamflow recession is used to account for the effects of geology on low flow. Streamflow recession rate depends primarily on transmissivity and storage characteristics of the aquifers, and average distance from stream channels to divides. Relations of low-flow discharge to geology, drainage area, and mean annual precipitation were analyzed by multiple regression techniques.

  18. Low-flow frequency and flow duration of selected South Carolina streams in the Savannah and Salkehatchie River Basins through March 2014

    USGS Publications Warehouse

    Feaster, Toby D.; Guimaraes, Wladmir B.

    2016-01-01

    An ongoing understanding of streamflow characteristics of the rivers and streams in South Carolina is important for the protection and preservation of the State’s water resources. Information concerning the low-flow characteristics of streams is especially important during critical flow periods, such as during the historic droughts that South Carolina has experienced in the past few decades.In 2008, the U.S. Geological Survey, in cooperation with the South Carolina Department of Health and Environmental Control, initiated a study to update low-flow statistics at continuous-record streamgaging stations operated by the U.S. Geological Survey in South Carolina. This report presents the low-flow statistics for 28 selected streamgaging stations in the Savannah and Salkehatchie River Basins in South Carolina. The low-flow statistics include daily mean flow durations for the 5-, 10-, 25-, 50-, 75-, 90-, and 95-percent probability of exceedance and the annual minimum 1-, 3-, 7-, 14-, 30-, 60-, and 90-day mean flows with recurrence intervals of 2, 5, 10, 20, 30, and 50 years, depending on the length of record available at the streamgaging station. The low-flow statistics were computed from records available through March 31, 2014.Low-flow statistics are influenced by length of record, hydrologic regime under which the data were collected, analytical techniques used, and other factors, such as urbanization, diversions, and droughts that may have occurred in the basin. To assess changes in the low-flow statistics from the previously published values, a comparison of the low-flow statistics for the annual minimum 7-day average streamflow with a 10-year recurrence interval (7Q10) from this study was made with the most recently published values. Of the 28 streamgaging stations for which recurrence interval computations were made, 14 streamgaging stations were suitable for comparing to low-flow statistics that were previously published in U.S. Geological Survey reports. These

  19. Low-flow frequency and flow duration of selected South Carolina streams in the Saluda, Congaree, and Edisto River basins through March 2009

    USGS Publications Warehouse

    Feaster, Toby D.; Guimaraes, Wladmir B.

    2012-01-01

    Part of the mission of the South Carolina Department of Health and Environmental Control and the South Carolina Department of Natural Resources is to protect and preserve South Carolina's water resources. Doing so requires an ongoing understanding of streamflow characteristics of the rivers and streams in South Carolina. A particular need is information concerning the low-flow characteristics of streams, which is especially important for effectively managing the State's water resources during critical flow periods, such as during periods of severe drought like South Carolina has experienced in the last decade or so. The U.S. Geological Survey, in cooperation with the South Carolina Department of Health and Environmental Control, initiated a study in 2008 to update low-flow statistics at continuous-record streamgaging stations operated by the U.S. Geological Survey in South Carolina. This report presents the low-flow statistics for 25 selected streamgaging stations in the Saluda, Congaree, and Edisto River basins in South Carolina, and includes flow durations for the 5-, 10-, 25-, 50-,75-, 90-, and 95-percent exceedances and the annual minimum 1-, 3-, 7-, 14-, 30-, 60-, and 90-day average flows with recurrence intervals of 2, 5, 10, 20, 30, and 50 years, depending on the length of record available at the streamgaging station. The low-flow statistics were computed from records available through March 31, 2009. Of the 25 streamgaging stations for which recurrence interval computations were made, 20 were compared to low-flow statistics that were published in previous U.S. Geological Survey reports. A comparison of the low-flow statistics for the annual minimum 7-day average streamflow with a 10-year recurrence interval (7Q10) from this study with the most recently published values indicates that 18 of the 20 streamgaging stations have values lower than the previous published values. The low-flow statistics are influenced by length of record, hydrologic regime under

  20. LFSTAT - Low-Flow Analysis in R

    NASA Astrophysics Data System (ADS)

    Koffler, Daniel; Laaha, Gregor

    2013-04-01

    The calculation of characteristic stream flow during dry conditions is a basic requirement for many problems in hydrology, ecohydrology and water resources management. As opposed to floods, a number of different indices are used to characterise low flows and streamflow droughts. Although these indices and methods of calculation have been well documented in the WMO Manual on Low-flow Estimation and Prediction [1], a comprehensive software was missing which enables a fast and standardized calculation of low flow statistics. We present the new software package lfstat to fill in this obvious gap. Our software package is based on the statistical open source software R, and expands it to analyse daily stream flow data records focusing on low-flows. As command-line based programs are not everyone's preference, we also offer a plug-in for the R-Commander, an easy to use graphical user interface (GUI) provided for R which is based on tcl/tk. The functionality of lfstat includes estimation methods for low-flow indices, extreme value statistics, deficit characteristics, and additional graphical methods to control the computation of complex indices and to illustrate the data. Beside the basic low flow indices, the baseflow index and recession constants can be computed. For extreme value statistics, state-of-the-art methods for L-moment based local and regional frequency analysis (RFA) are available. The tools for deficit characteristics include various pooling and threshold selection methods to support the calculation of drought duration and deficit indices. The most common graphics for low flow analysis are available, and the plots can be modified according to the user preferences. Graphics include hydrographs for different periods, flexible streamflow deficit plots, baseflow visualisation, recession diagnostic, flow duration curves as well as double mass curves, and many more. From a technical point of view, the package uses a S3-class called lfobj (low-flow objects). This

  1. Regression equations to estimate seasonal flow duration, n-day high-flow frequency, and n-day low-flow frequency at sites in North Dakota using data through water year 2009

    USGS Publications Warehouse

    Williams-Sether, Tara; Gross, Tara A.

    2016-01-01

    Seasonal mean daily flow data from 119 U.S. Geological Survey streamflow-gaging stations in North Dakota; the surrounding states of Montana, Minnesota, and South Dakota; and the Canadian provinces of Manitoba and Saskatchewan with 10 or more years of unregulated flow record were used to develop regression equations for flow duration, n-day high flow and n-day low flow using ordinary least-squares and Tobit regression techniques. Regression equations were developed for seasonal flow durations at the 10th, 25th, 50th, 75th, and 90th percent exceedances; the 1-, 7-, and 30-day seasonal mean high flows for the 10-, 25-, and 50-year recurrence intervals; and the 1-, 7-, and 30-day seasonal mean low flows for the 2-, 5-, and 10-year recurrence intervals. Basin and climatic characteristics determined to be significant explanatory variables in one or more regression equations included drainage area, percentage of basin drainage area that drains to isolated lakes and ponds, ruggedness number, stream length, basin compactness ratio, minimum basin elevation, precipitation, slope ratio, stream slope, and soil permeability. The adjusted coefficient of determination for the n-day high-flow regression equations ranged from 55.87 to 94.53 percent. The Chi2 values for the duration regression equations ranged from 13.49 to 117.94, whereas the Chi2 values for the n-day low-flow regression equations ranged from 4.20 to 49.68.

  2. Low-flow characteristics of streams West Virginia

    USGS Publications Warehouse

    Friel, E.A.; Embree, W.N.; Jack, A.R.; Atkins, J.T., Jr.

    1989-01-01

    Low-flow characteristics of selected streams in West Virginia were determined at continuous-record and partial-record sites. Daily discharges at 100 continuous-record gaging stations on unregulated streams were used to compute selected low-flow frequency values. Estimates of low-flow frequency values at 296 partial-record sites (ones having only discharge measurements) were made using the relation defined by concurrent flows with a continuous-record station. Low-flow characteristics at continuous-record stations were related to drainage area and a variability index to produce equations which can be used to estimate low-flow characteristics at ungaged sites in West Virginia. The State was divided into two hydrologic regions. Drainage area and a streamflow-variability index were determined to be the most significant. The streamflow variability index was computed from duration curves and was used to account for the integrated effects of geology and other hydrologic characteristics. The standard error of estimate for the 7-day low flow with a 2-year recurrence interval is 43% for Region 1 and 57% for Region 2. The standard error of estimate for the 7-day low flow with a 10-year recurrence interval is 82% for Region 1 and 83% for Region 2. (USGS)

  3. Annual and seasonal low-flow characteristics of Iowa streams

    USGS Publications Warehouse

    Lara, Oscar G.

    1979-01-01

    The low-flow characteristics of Iowa streams are described by annual and seasonal low-flow frequency and duration data. Tabulated in this report are low-flow data collected at 135 gaging stations on Iowa streams, three on the Mississippi River, four on the Missour River, and 426 partial-record sites. The information contained in this report is based on all of the daily discharge records collected by the U.S. Geological Survey through the 1976 water year. Consideration is given to the regional aspects of low-flow characteristics by including regression equations to estimate the average discharge and generalized maps to estimate the 7-day, 2-year and 7-day, 10-year discharges at ungaged sites. (Kosco-USGS)

  4. 77 FR 17563 - Low Flow Protection Policy

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-26

    ... From the Federal Register Online via the Government Publishing Office SUSQUEHANNA RIVER BASIN COMMISSION Low Flow Protection Policy AGENCY: Susquehanna River Basin Commission. ACTION: Notice. SUMMARY: As... Susquehanna River Basin Commission (Commission) approved the release of a proposed Low Flow Protection...

  5. Low-flow characteristics of Virginia streams

    USGS Publications Warehouse

    Austin, Samuel H.; Krstolic, Jennifer L.; Wiegand, Ute

    2011-01-01

    Low-flow annual non-exceedance probabilities (ANEP), called probability-percent chance (P-percent chance) flow estimates, regional regression equations, and transfer methods are provided describing the low-flow characteristics of Virginia streams. Statistical methods are used to evaluate streamflow data. Analysis of Virginia streamflow data collected from 1895 through 2007 is summarized. Methods are provided for estimating low-flow characteristics of gaged and ungaged streams. The 1-, 4-, 7-, and 30-day average streamgaging station low-flow characteristics for 290 long-term, continuous-record, streamgaging stations are determined, adjusted for instances of zero flow using a conditional probability adjustment method, and presented for non-exceedance probabilities of 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, 0.05, 0.02, 0.01, and 0.005. Stream basin characteristics computed using spatial data and a geographic information system are used as explanatory variables in regional regression equations to estimate annual non-exceedance probabilities at gaged and ungaged sites and are summarized for 290 long-term, continuous-record streamgaging stations, 136 short-term, continuous-record streamgaging stations, and 613 partial-record streamgaging stations. Regional regression equations for six physiographic regions use basin characteristics to estimate 1-, 4-, 7-, and 30-day average low-flow annual non-exceedance probabilities at gaged and ungaged sites. Weighted low-flow values that combine computed streamgaging station low-flow characteristics and annual non-exceedance probabilities from regional regression equations provide improved low-flow estimates. Regression equations developed using the Maintenance of Variance with Extension (MOVE.1) method describe the line of organic correlation (LOC) with an appropriate index site for low-flow characteristics at 136 short-term, continuous-record streamgaging stations and 613 partial-record streamgaging stations. Monthly

  6. Low-flow characteristics of streams on the Olympic Peninsula, Washington

    USGS Publications Warehouse

    Haushild, W.L.; LaFrance, D.E.

    1977-01-01

    Streams in lowland basins of the Olympic Peninsula, Washington, generally have their low flows in summer and peak flows in winter, whereas streams originating at higher elevations in the mountains have their low flows in late summer-early fall and they have both winter and spring peak flows. Data from long-term stations indicate no important trend in low flows during 1940-73 but they do indicate that low flows generally were lower during the relatively dry 1940 's than during the relatively wet 1950-73 period. The magnitude and frequency of 7-day low flows were estimated for 116 sites either from frequency analyses of a data at long-term stations or from correlation of data at a short-term station with data at an appropriate long-term station. (Woodard-USGS)

  7. Simulation of streamflow of Flambeau River at Park Falls, Wisconsin to define low-flow characteristics

    USGS Publications Warehouse

    Krug, William R.

    1976-01-01

    Daily streamflows of the Flambeau River at Park Falls, Wisconsin , were simulated for a 31-year period. Streamflow was simulated using a streamflow-routing model. These simulated daily flows were analyzed for summer (June 1-October 31) low-flow frequency. The resultant 7-day, 10-year summer low flow is 260 cubic feet per second. The standard error of estimate for this 10-year-frequency low flow is equivalent to the standard error of estimate for 16 years of gaging-station records.

  8. Bootstrap position analysis for forecasting low flow frequency

    USGS Publications Warehouse

    Tasker, Gary D.; Dunne, P.

    1997-01-01

    A method of random resampling of residuals from stochastic models is used to generate a large number of 12-month-long traces of natural monthly runoff to be used in a position analysis model for a water-supply storage and delivery system. Position analysis uses the traces to forecast the likelihood of specified outcomes such as reservoir levels falling below a specified level or streamflows falling below statutory passing flows conditioned on the current reservoir levels and streamflows. The advantages of this resampling scheme, called bootstrap position analysis, are that it does not rely on the unverifiable assumption of normality, fewer parameters need to be estimated directly from the data, and accounting for parameter uncertainty is easily done. For a given set of operating rules and water-use requirements for a system, water managers can use such a model as a decision-making tool to evaluate different operating rules. ?? ASCE,.

  9. Protect centrifugal pumps from low flows

    SciTech Connect

    Woodside, O.

    1995-06-01

    Operation of centrifugal pumps below their minimum flow requirements is the primary cause of premature pump failure. Hydraulic instability occurs at low flows, causing cavitation, surging, and excessive vibration in the pump. This instability is more restrictive in setting the minimum allowable flow than using the temperature rise, which was used in the past. If you are the system design engineer, you should consider providing a protective system during the preparation of the piping and instrumentation diagrams (P and IDs). Not all pumps require a protective system. Your problem is to determine which pumps do and which do not, and decide the type of system to employ. This decision must be made as early as possible in the development of the P and IDs to avoid costly rework. This article gives guidelines on when to provide a protective system and offers examples of appropriate designs.

  10. Nonstationarity of low flows and their timing in the eastern United States

    NASA Astrophysics Data System (ADS)

    Sadri, S.; Kam, J.; Sheffield, J.

    2016-02-01

    The analysis of the spatial and temporal patterns of low flows as well as their generation mechanisms over large geographic regions can provide valuable insights and understanding for climate change impacts, regional frequency analysis, risk assessment of extreme events, and decision-making regarding allowable withdrawals. The goal of this paper is to examine nonstationarity in low flow generation across the eastern US and explore the potential anthropogenic influences or climate drivers. We use nonparametric tests to identify abrupt and gradual changes in time series of low flows and their timing for 508 USGS streamflow gauging sites in the eastern US with more than 50 years of daily data, to systematically distinguish the effects of human intervention from those of climate variability. A time series decomposition algorithm was applied to 1-day, 7-day, 30-day, and 90-day annual low flow time series that combines the Box-Ljung test for detection of autocorrelation, the Pettitt test for abrupt step changes and the Mann-Kendall test for monotonic trends. Examination of the USGS notes for each site showed that many of the sites with step changes and around half of the sites with an increasing trend have been documented as having some kind of regulation. Sites with decreasing or no trend are less likely to have documented influences on flows. Overall, a general pattern of increasing low flows in the northeast and decreasing low flows in the southeast is evident over a common time period (1951-2005), even when discarding sites with significant autocorrelation, documented regulation or other human impacts. The north-south pattern of trends is consistent with changes in antecedent precipitation. The main exception is along the mid-Atlantic coastal aquifer system from eastern Virginia northwards, where low flows have decreased despite increasing precipitation, and suggests that declining groundwater levels due to pumping may have contributed to decreased low flows. For

  11. The effects of groundwater abstraction on low flows

    NASA Astrophysics Data System (ADS)

    de Graaf, I. E. M.; van Beek, L. P. H.; Wada, Y.; Bierkens, M. F. P.

    2012-04-01

    In regions with frequent water stress and large aquifer systems, groundwater often constitutes an essential source of water. If groundwater abstraction exceeds groundwater recharge over a long time and over large areas persistent groundwater depletion can occur. The resulting lowering of groundwater levels can have negative effects on agricultural productivity but also on natural streamflow and associated wetlands and ecosystems, in particular during low-flow events when the groundwater contribution through baseflow is relatively large. In this study we focus on the effects of global groundwater abstraction on low-flow magnitude, frequency and duration for the major rivers of the world for the period 1960-2000. As a basis, we use the large-scale hydrological model PCR-GLOBWB that calculates all major water balance terms on a daily time step at a 0.5ox0.5o resolution. Currently, PCR-GLOBWB represents groundwater and the associated baseflow by means of a linear reservoir that is parameterized using global lithological data and drainage density. It simulates renewable groundwater storage within each 0.5o cell. Lateral flow between cells is not considered. The specific runoff from the model is subsequently transformed into discharge by means of a kinematic wave routing scheme. In this study we perform a sensitivity analysis in which we evaluate the effects of total water demand for the period 1960-2000 (Wada et al., 2011: doi:10.5194/hess-15-3785-2011). This demand is preferentially met by renewable groundwater storage, secondly by surface water. Any remainder is assumed to stem from non- renewable (i.e. fossil) groundwater resources. Thus, groundwater abstractions act as a direct sink of (renewable) groundwater storage, whereas surface water abstractions act as a direct sink of streamflow. The resulting response is non-trivial as abstractions are variably taken from both groundwater and surface water, where return-flows contribute to a single source: return flow from

  12. [Nitrous oxide free low-flow anesthesia].

    PubMed

    Baum, J; Sievert, B; Stanke, H G; Brauer, K; Sachs, G

    2000-01-01

    The routine use of nitrous oxide as a component of the carrier gas has been unanimously called into question in recent surveys, in fact, its use is now recommended in indicated cases only. Whereas a lot of contraindications are listed in the surveys, precise definitions of justified indications are not given. In clinical routine practice, there are absolutely no problems in carrying out inhalational anaesthesia without nitrous oxide. The missing analgetic effect can be compensated for by moderately increasing the additively used amount of opioids, while the missing hypnotic effect can be achieved by raising the expired concentration of the inhalational anaesthetic by not more than 0.2-0.25 x MAC. Thus, when isoflurane is used, an expired concentration of 1.2 vol% is desired, in the case of sevoflurane of 2.2 vol% and with desflurane of 5.0 vol%. In addition, doing without nitrous oxide facilitates the performance of low flow anaesthetic techniques considerably. Since the patient only inhales oxygen and the volatile anaesthetic, the total gas uptake is reduced significantly. Washing out nitrogen is no longer necessary. This means that the initial phase of low flow anaesthesia, during which high fresh gas flows have to be used, can be kept short. Its duration is now determined by the wash-in of the volatile anaesthetic. Since there is no uptake of nitrous oxide, a considerably greater volume of gas is circulating within the breathing system, minimizing the possibility of accidental gas volume deficiency. Thus, if anaesthesia machines with highly gas-tight breathing systems are used, even the performance of non-quantitative closed system anaesthesia becomes possible in routine clinical practice. The carrier gas flow can be reduced to just that amount of oxygen which is really taken up by the patient. This oxygen volume can be roughly calculated by applying the Brody's formula. Using fresh gas flows as low as 0.25 l/min, however, will result in a significant decrease

  13. Calculation and optimization of parameters in low-flow pumps

    NASA Astrophysics Data System (ADS)

    Kraeva, E. M.; Masich, I. S.

    2016-04-01

    The materials on balance tests of high-speed centrifugal pumps with low flow rate are presented. On the bases of analysis and research synthesis, we demonstrate the rational use of impellers of semi-open and open types providing high values for energy parameters of feed system of low-flow pumps.

  14. Uncertainty contributions to low-flow projections in Austria

    NASA Astrophysics Data System (ADS)

    Parajka, Juraj; Blaschke, Alfred Paul; Blöschl, Günter; Haslinger, Klaus; Hepp, Gerold; Laaha, Gregor; Schöner, Wolfgang; Trautvetter, Helene; Viglione, Alberto; Zessner, Matthias

    2016-05-01

    The main objective of the paper is to understand the contributions to the uncertainty in low-flow projections resulting from hydrological model uncertainty and climate projection uncertainty. Model uncertainty is quantified by different parameterisations of a conceptual semi-distributed hydrologic model (TUWmodel) using 11 objective functions in three different decades (1976-1986, 1987-1997, 1998-2008), which allows for disentangling the effect of the objective function-related uncertainty and temporal stability of model parameters. Climate projection uncertainty is quantified by four future climate scenarios (ECHAM5-A1B, A2, B1 and HADCM3-A1B) using a delta change approach. The approach is tested for 262 basins in Austria. The results indicate that the seasonality of the low-flow regime is an important factor affecting the performance of model calibration in the reference period and the uncertainty of Q95 low-flow projections in the future period. In Austria, the range of simulated Q95 in the reference period is larger in basins with a summer low-flow regime than in basins with a winter low-flow regime. The accuracy of simulated Q95 may result in a range of up to 60 % depending on the decade used for calibration. The low-flow projections of Q95 show an increase of low flows in the Alps, typically in the range of 10-30 % and a decrease in the south-eastern part of Austria mostly in the range -5 to -20 % for the climate change projected for the future period 2021-2050, relative the reference period 1978-2007. The change in seasonality varies between scenarios, but there is a tendency for earlier low flows in the northern Alps and later low flows in eastern Austria. The total uncertainty of Q95 projections is the largest in basins with a winter low-flow regime and, in some basins the range of Q95 projections exceeds 60 %. In basins with summer low flows, the total uncertainty is mostly less than 20 %. The ANOVA assessment of the relative contribution of the three

  15. Low-flow characteristics of streams in the Deschutes River basin, Washington

    USGS Publications Warehouse

    Cummans, J.E.

    1981-01-01

    The streams in the basin usually have their low flows in August and September. Seven-day low flows were smallest in 1952 when annual rainfall at the Olympia airport was also the least during the 1945-75 period of continuous gaging-station records in the basin. The magnitude and frequency of seven-day low flows were estimated for 23 streamflow sites, either from frequency analysis of data at long-term stations or from correlation of measured or computed discharges at a streamflow site with data at a long-term station. Seven-day low flows ranged from no-flow at one tributary of Deschutes River having a drainage area of 1.85 square miles to 98 cubic feet per second for Deschutes River near its mouth, where the drainage was 162 square miles. Mean monthly flows were determined for two long-term stations and estimated for months of July to September for the other streamflow sites. (USGS)

  16. Regionalization of winter low-flow characteristics of Tennessee streams

    USGS Publications Warehouse

    Bingham, R.H.

    1986-01-01

    Procedures were developed for estimating winter (December-April) low flows at ungaged stream sites in Tennessee based on surface geology and drainage area size. One set of equations applies to West Tennessee streams, and another set applies to Middle and East Tennessee streams. The equations do not apply to streams where flow is significantly altered by the activities of man. Standard errors of estimate of equations for West Tennessee are 22% - 35% and for middle and East Tennessee 31% - 36%. Statistical analyses indicate that summer low-flow characteristics are the same as annual low-flow characteristics, and that winter low flows are larger than annual low flows. Streamflow-recession indexes, in days per log cycle of decrease in discharge, were used to account for effects of geology on low flow of streams. The indexes in Tennessee range from 32 days/log cycle for clay and shale to 350 days/log cycle for gravel and sand, indicating different aquifer characteristics of the geologic units that contribute to streamflows during periods of no surface runoff. Streamflow-recession rate depends primarily on transmissivity and storage characteristics of the aquifers, and the average distance from stream channels to basin divides. Geology and drainage basin size are the most significant variables affecting low flow in Tennessee streams according to regression analyses. (Author 's abstract)

  17. Low flows and flow duration of Tennessee streams through 1981

    USGS Publications Warehouse

    Bingham, R.H.

    1985-01-01

    Estimates of low-flow characteristics and flow duration for the period of record at continuous-record streamflow gages are essential in hydrologic studies and water-resources management. This report provides estimates of low flow for 1, 3, 7, 14, 30, 60, and 90 consecutive days for recurrence intervals of 2, 5, 10 , and 20 years for continuous-record streamflow gages in Tennessee. These estimates were used in correlation methods to estimate low flow at partial-record streamflow sites for 1, 3, and 7 consecutive days for a recurrence interval of 10 years; and 3 consecutive days for a recurrence interval of 20 years. (USGS)

  18. Regionalized rainfall-runoff model to estimate low flow indices

    NASA Astrophysics Data System (ADS)

    Garcia, Florine; Folton, Nathalie; Oudin, Ludovic

    2016-04-01

    Estimating low flow indices is of paramount importance to manage water resources and risk assessments. These indices are derived from river discharges which are measured at gauged stations. However, the lack of observations at ungauged sites bring the necessity of developing methods to estimate these low flow indices from observed discharges in neighboring catchments and from catchment characteristics. Different estimation methods exist. Regression or geostatistical methods performed on the low flow indices are the most common types of methods. Another less common method consists in regionalizing rainfall-runoff model parameters, from catchment characteristics or by spatial proximity, to estimate low flow indices from simulated hydrographs. Irstea developed GR2M-LoiEau, a conceptual monthly rainfall-runoff model, combined with a regionalized model of snow storage and melt. GR2M-LoiEau relies on only two parameters, which are regionalized and mapped throughout France. This model allows to cartography monthly reference low flow indices. The inputs data come from SAFRAN, the distributed mesoscale atmospheric analysis system, which provides daily solid and liquid precipitation and temperature data from everywhere in the French territory. To exploit fully these data and to estimate daily low flow indices, a new version of GR-LoiEau has been developed at a daily time step. The aim of this work is to develop and regionalize a GR-LoiEau model that can provide any daily, monthly or annual estimations of low flow indices, yet keeping only a few parameters, which is a major advantage to regionalize them. This work includes two parts. On the one hand, a daily conceptual rainfall-runoff model is developed with only three parameters in order to simulate daily and monthly low flow indices, mean annual runoff and seasonality. On the other hand, different regionalization methods, based on spatial proximity and similarity, are tested to estimate the model parameters and to simulate

  19. Low flow veno-venous ECMO: an experimental study.

    PubMed

    Calderón, M; Verdín, R; Galván, J; Gonzalez, M; Cárdenas, H; Campos, R; Vidrio, H; Amezcua, J

    1994-01-01

    Clinical use of extracorporeal membrane oxygenation (ECMO) and carbon dioxide removal (ECCO 2R) have become well established techniques for the treatment of severe respiratory failure; however they require full cardiopulmonary bypass, representing major procedures with high morbidity. We theorized the possibility of an efficient low flow veno-venous extracorporeal membrane gas exchange method. Four mongrel 12 kg dogs were submitted to veno-venous extracorporeal membrane gas exchange via a jugular dialysis catheter using a low flow (10 ml/min) roller pump and a membrane oxygenator for a period of four hours. Respiratory rate was set at 4 breaths/min with a FiO 2 of 21% and ventilatory dead space was increased. Adequate gas exchange was obtained (pO 2139, pCO 224, Sat 99.4%), without major hemodynamic changes or hematuria. Our results demonstrate the feasibility of a low flow, less aggressive system. Further research should be considered. PMID:10147372

  20. Detection and effects of pump low-flow operation

    SciTech Connect

    Casada, D.A.; Greene, R.H.

    1993-12-01

    Operating experience and previous studies have shown that a significant cause of pump problems and failures can result from low- flow operation. Operation at low-flow rates can create unstable flows within the pump impeller and casing. This condition can result in an increased radial and axial thrust on the rotor, which in turn causes higher shaft stresses, increased shaft deflection, and potential bearing and mechanical seal problems. Two of the more serious results of low-flow pump operation are cavitation and recirculation. Cavitation is the formation and subsequent collapse of vapor bubbles in any flow that is at an ambient pressure less than the vapor pressure of the liquid medium. It is the collapse of these vapor bubbles against the metal surfaces of the impeller or casing that causes surface pitting, erosion, and deterioration. Pump recirculation more damaging than cavitation. If located at the impeller eye, recirculation damages the inlet areas of the casing. At the impeller tips, recirculation alters the outside diameter of the impeller. If recirculation occurs around impeller shrouds, it damages thrust bearings. Recirculation also erodes impellers, diffusers, and volutes and causes failure of mechanical seals and bearings. This paper reports on a utility pump failure caused by low-flow induced phenomena. ORNL is investigating the results of low-flow pump operations by evaluating the types of measurements and diagnostic techniques that are currently used by licensees to detect pump degradation. A new, enhanced application of motor current and power data analysis has been developed that uses a signal comparison methodology to produce an instability ratio indicative of normal or unstable flow conditions. Examples of this type of low-flow detection technique are presented in this paper along with a brief discussion of the various types of technologies currently being used by licensees to evaluate pump operation and determine possible degradation.

  1. Statistical Modeling of Low Flow Conditions based on Climatic Indicators

    NASA Astrophysics Data System (ADS)

    Fangmann, Anne; Haberlandt, Uwe

    2015-04-01

    Regression-based approaches in climate change impact assessment may pose a practical alternative to the application of process-based hydrological models, especially with respect to low flow extremes. Extended durations and spatial dimensions allow for a quantitative assessment and exploitation of the interrelations between atmospheric driving forces and streamflow response during dry periods, and eventually for the prognosis of future low flow conditions based on climate model input. This study aims at using combinations of climatic indicators, quantifying a variety of meteorological drought characteristics, to model specific low flow indices, based solely on multiple linear regressions. The area under investigation is the federal state of Lower Saxony, Germany. Daily time series of climate and streamflow data pose the basis for calculation of a set of meteorological and hydrological indices, serving as regressors and regressands, respectively. Two approaches are being analyzed: a) a station-based approach, fitting a specific regression equation at each discharge gauge with sufficient record length, and b) a regional approach, enabling the estimation of low flow indices at ungauged sites and stations with minor record length. The station-based procedure is used for estimation of annual low flow index values from annual meteorological conditions. Subsequent fitting of distribution functions to the estimated values allows for the assessment of return periods of the low flow indices. The regionalization, on the other hand, is designed to directly estimate the shapes of the distribution functions by applying L-moment regressions, enabling a direct assessment of specific index values for the return periods in demand.

  2. PARTICULATE ORGANIC CARBON MEASUREMENTS COLLECTED WITH LOW FLOW PERSONAL SAMPLERS

    EPA Science Inventory

    EPA's National Exposure Research Laboratory and the Research Triangle Institute (RTI) have conducted a particulate matter (PM) personal exposure study in Research Triangle Park, NC. Particulate carbon was sampled with pre-fired quartz filters using low flow PM2.5 samplers (2 L...

  3. Observed low flow trends in major US river basins

    NASA Astrophysics Data System (ADS)

    Pournasiri Poshtiri, M.; Pal, I.

    2014-12-01

    Changes in global climate would likely be associated with impacts on regional hydrological cycle, such as changes in variability of precipitation and stream flow. Hence, to formulate and implement climate risk management strategies, it is essential to detect where and when hydrological extremes have been changing and to what extent. This scientific research presents where and how low flow characteristics, particularly the occurrence, intensity and severity of hydrological extremes, have been changing in fourteen major river basins within the continental U.S. Of particular interest is to detect if monotonic trends in low flow characteristics shifted with decades, reflecting the known climatic shifts, particularly before and after 1980. Persistent low flow conditions in a river can directly influence water supply for domestic, agricultural, industrial, ecological, and other needs; and a monotonic trend in such persistent low flow condition can lead to chronic water scarcity—a main driver of societal and cross-boundary conflicts around the world. Thus, outcomes from this research are instrumental for the water managers to develop suitable adaptive management measures at the locations and times of need.

  4. Low flow trends in the eastern United States

    NASA Astrophysics Data System (ADS)

    Sadri, S.; Sheffield, J.

    2012-12-01

    Low flows are an important part of the flow regime that have direct impacts on water supply, water quality and ecosystem health. In this study we evaluate changes in low flows in the eastern US over the past 30-70 years based on a filtered set of USGS gauging stations. Our goals are: (1) to help systematically distinguish the effects of human intervention from those of climate variability and change, (2) to use and compare nonparametric tests for identifying abrupt change points in the time series, (3) to identify significant overall trends in the low flow time series, and (4) to attribute the spatial pattern of natural changes in low flows to changes in precipitation and other climatic drivers. We started with 4878 surface stream gages in the eastern US with daily data but we used only 523 sites that had 50 years worth of daily data and did not have any annual gaps in their data. For each year of the data, we calculated the minimum n-day (n is equal to 1, 7, 30, and 90) low flow values to represent low-flows at various time scales, each of which is important to various sectors, such as for minimum environmental flows or water supply. In many hydrological methods sites are typically required to be "unregulated," (not affected by man-made artifacts such as dams). An alternative to survey notes is to apply statistical tests to identify step changes in the data series that are likely due to human intervention. This is generally more efficient and can complement survey notes or compensate for errors. We evaluated the regime shifts in the minimum n-day low flow time series for the 523 gauges using two different step change tests: Pettitt and Rodionov tests. Examination of survey notes for a subset of these confirmed that many of the largest step changes are associated with dam construction. However, several sites showed significant changes but had no record of human intervention. Additionally, whether a human change has a significant effect on a gauge time series should

  5. Low-flow and flow-duration characteristics of Alabama streams

    USGS Publications Warehouse

    Atkins, J.B.; Pearman, J.L.

    1994-01-01

    Estimates of minimum 7-day average discharges with recurrence intervals of 2 and 10 years for 228 continuous-record gaging stations are presented in this report. Low-flow frequency discharge estimates for 447 partial-record stations are also presented. These discharge estimates were computed by relating base-flow discharge measurements at the partial- record stations to daily-mean discharge values at selected continuous-record gaging stations. Flow- duration characteristics for 207 continuous-record gaging stations are also provided.

  6. Regionalization of low-flow characteristics of Tennessee streams

    USGS Publications Warehouse

    Bingham, R.H.

    1986-01-01

    Procedures for estimating 3-day 2-year, 3-day 10-year, 3-day 20-year, and 7-day 10-year low flows at ungaged stream sites in Tennessee are based on surface geology and drainage area size. One set of equations applies to west Tennessee streams, and another set applies to central and east Tennessee streams. The equations do not apply to streams where flow is significantly altered by activities of man. Standard errors of estimate of equations for west Tennessee are 24 to 32% and for central and east Tennessee 31 to 35%. Streamflow recession indexes, in days/log cycle, are used to account for effects of geology of the drainage basin on low flow of streams. The indexes in Tennessee range from 32 days/log cycle for clay and shale to 350 days/log cycle for gravel and sand, indicating different aquifer characteristics of the geologic units that sustain streamflows during periods of no surface runoff. Streamflow recession rate depends primarily on transmissivity and storage characteristics of the aquifers, and the average distance from stream channels to basin divides. Geology and drainage basin size are the most significant variables affecting low flow in Tennessee streams according to regression analyses. (Author 's abstract)

  7. Monthly to seasonal low flow prediction: statistical versus dynamical models

    NASA Astrophysics Data System (ADS)

    Ionita-Scholz, Monica; Klein, Bastian; Meissner, Dennis; Rademacher, Silke

    2016-04-01

    While the societal and economical impacts of floods are well documented and assessable, the impacts of lows flows are less studied and sometimes overlooked. For example, over the western part of Europe, due to intense inland waterway transportation, the economical loses due to low flows are often similar compared to the ones due to floods. In general, the low flow aspect has the tendency to be underestimated by the scientific community. One of the best examples in this respect is the facts that at European level most of the countries have an (early) flood alert system, but in many cases no real information regarding the development, evolution and impacts of droughts. Low flows, occurring during dry periods, may result in several types of problems to society and economy: e.g. lack of water for drinking, irrigation, industrial use and power production, deterioration of water quality, inland waterway transport, agriculture, tourism, issuing and renewing waste disposal permits, and for assessing the impact of prolonged drought on aquatic ecosystems. As such, the ever-increasing demand on water resources calls for better a management, understanding and prediction of the water deficit situation and for more reliable and extended studies regarding the evolution of the low flow situations. In order to find an optimized monthly to seasonal forecast procedure for the German waterways, the Federal Institute of Hydrology (BfG) is exploring multiple approaches at the moment. On the one hand, based on the operational short- to medium-range forecasting chain, existing hydrological models are forced with two different hydro-meteorological inputs: (i) resampled historical meteorology generated by the Ensemble Streamflow Prediction approach and (ii) ensemble (re-) forecasts of ECMWF's global coupled ocean-atmosphere general circulation model, which have to be downscaled and bias corrected before feeding the hydrological models. As a second approach BfG evaluates in cooperation with

  8. Low-flow characteristics and profiles for the Deep River in the Cape Fear River basin, North Carolina

    USGS Publications Warehouse

    Weaver, J.C.

    1997-01-01

    An understanding of the magnitude and frequency of low-flow discharges is an important part of protecting surface-water resources and planning for municipal and industrial economic expansion. Low-flow characteristics are summarized for 7 continuous-record gaging stations and 23 partial-record measuring sites in the Deep River Basin in North Carolina. Records of discharge collected through the 1995 water year are used. Flow characteristics included in the summary are (1) average annual unit flow; (2) 7Q10 low-flow discharge, the minimum average discharge for a 7-consecutive-day period occurring, on average, once in 10 years; (3) 30Q2 low-flow discharge; (4) W7Q10 low-flow discharge, similar to 7Q10 discharge except only flow during the months of November through March is considered; and (5) 7Q2 low-flow discharge. The potential for sustained base flows in the upper half of the basin is higher than that for streams in the lower half of the basin. Much of the decrease in base-flow potential in the lower part of the basin is attributed to the underlying rock types of the Triassic basin. Soils in the lower part of the basin consist of clays which limit the infiltration of water into surficial aquifers for later release to streams during drought conditions. Correspondingly, many streams in the lower part of the basin have minimal (defined as less than 0.1 cubic foot per second) or zero 7Q10 discharges. Drainage area and low-flow discharge profiles are presented for the Deep River. The drainage-area profile shows downstream increases in basin size. At the mouth, the drainage area for the Deep River is 1,441 square miles. Low-flow discharge profiles for the Deep River include 7Q10, 30Q2, W7Q10, and 7Q2 discharges in a continuous profile with contributions from major tributaries included.

  9. Uncertainty in low-flow data from three streamflow-gaging stations on the upper Verde River, Arizona

    USGS Publications Warehouse

    Anning, D.W.

    2004-01-01

    The evaluation of uncertainty in low-flow data collected from three streamflow-gaging stations on the upper Verde River, Arizona, was presented. In downstream order, the stations are Verde River near Paulden, Verde River near Clarkdale, and Verde River near Camp Verde. A monitoring objective of the evaluation was to characterize discharge of the lower flow regime through a variety of procedures such as frequency analysis and base-flow analysis. For Verde River near Paulden and near Camp Verde, the uncertainty of daily low flows can be reduced by decreasing the uncertainty of discharge-measurement frequency, or building an artificial control that would have a stable stage-discharge relation over time.

  10. [Low-flow xenon anesthesia in surgical patients with hypertension].

    PubMed

    Rashchupkin, A B; Burov, N E

    2011-01-01

    A comparative study of central hemodynamics in 60 patients with essential hypertension during low flow anesthesia with xenon and nitrous oxide is carried out. The main group consisted of 30 patients, 22 male and 8 female, in the median age of 45.9 +/- 23 years. 22 patients out of those had 2nd stage essential hypertension, while the other 8 had 3rd stage. The control group consisted of 30 patients, 20 male and 10 female, in the median age of 45.1 + 1.3 years. 4 patients had 3rd stage essential hypertension, 26 patients had 2nd stage. The both groups were clinically comparable by the character and severity of the main disease, the carried out surgery (open cholecystectomy) and the qualification of surgeons. Results of the research showed, that low flow monoanesthesia with xenon abruptly eradicated the unfavourable consequences of induction of anesthesia (3-5 mg/kg of sodium thiopental or 2-2.5 mg/kg of propofol) and had a positive effect on the parameters of central hemodynamics of patients with essential hypertension. Xenon anesthesia, compared to nitrous oxide, rapidly stabilized the parameters of blood pressure and heart rate and can be recommended as a method of choice in patients with essential hypertension and compromised myocarium. Nitrous oxide with bolus of regular fentanyl doses doesn't reliable anesthesiological protection during open cholecystectomy and shows signs of toxicity. PMID:21692217

  11. Influence of fracture intersections under unsaturated, low flow conditions

    SciTech Connect

    Thomas R. Wood; Michael J. Nicholl; Robert J. Glass

    2005-04-01

    Recent experimental evidence suggests that the capillary heterogeneity associated with fracture intersections can act to impose temporal and spatial structure on network-scale flows. A simple intersection between orthogonal fractures, one horizontal and the other vertical, has been shown to integrate unsaturated flows. At low flows the intersection forms a capillary barrier that accumulates water in a growing pool. Eventually, the retaining meniscus snaps, discharging a pulse of water. Here we develop a mechanistic explanation for this observed behavior and experimentally consider three perturbations to the geometry of the simple orthogonal intersection. Two of the perturbations also act as capillary barriers, while the third formed a capillary bridge across the intersection. At low flow, all of our experimental intersections imposed a temporal signal, with the nature of that signal dependent on intersection geometry and participation by the horizontal fractures in dynamic storage. At high flow a continuous fluid tendril spanned the system from inlet to outlet with water pooled above the intersection caused by a narrow fluid connection that restricted flow across the intersection. Results from all experiments suggest that pulsation is critically sensitive to small variations in the geometry of fracture intersections and storage in the horizontal fractures. When combined with dependency on supply rate, this sensitivity can generate pulsation of flow across a wide range of time periods and discharge volumes.

  12. Evaluation of an ultra low-flow water delivery system for small experimental tanks

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An ultra low-flow water delivery system was developed and tested for use in research studies requiring low-flow in small water volumes. Small test systems save on the amount of fish, chemicals, and biologics needed in disease challenge and treatment experiments. The ultra low-flow system, comprise...

  13. A method for characterizing late-season low-flow regime in the upper Grand Ronde River Basin, Oregon

    USGS Publications Warehouse

    Kelly, Valerie J.; White, Seth

    2016-01-01

    This report describes a method for estimating ecologically relevant low-flow metrics that quantify late‑season streamflow regime for ungaged sites in the upper Grande Ronde River Basin, Oregon. The analysis presented here focuses on sites sampled by the Columbia River Inter‑Tribal Fish Commission as part of their efforts to monitor habitat restoration to benefit spring Chinook salmon recovery in the basin. Streamflow data were provided by the U.S. Geological Survey and the Oregon Water Resources Department. Specific guidance was provided for selection of streamgages, development of probabilistic frequency distributions for annual 7-day low-flow events, and regionalization of the frequency curves based on multivariate analysis of watershed characteristics. Evaluation of the uncertainty associated with the various components of this protocol indicates that the results are reliable for the intended purpose of hydrologic classification to support ecological analysis of factors contributing to juvenile salmon success. They should not be considered suitable for more standard water-resource evaluations that require greater precision, especially those focused on management and forecasting of extreme low-flow conditions.

  14. A Tree-Ring Derived Reconstruction of Regionalized Low-Flow Season Streamflow for Susceptible Watersheds in South Coastal British Columbia, Canada.

    NASA Astrophysics Data System (ADS)

    Coulthard, B. L.; Smith, D. J.

    2014-12-01

    Rising winter air temperatures, snowpack declines, and warmer and drier summers have resulted in an increase in the frequency and severity of late-summer low-flow events across south coastal British Columbia. Negative impacts, particularly those associated with deteriorating water quality, decreased water supply for hydroelectric power generation, and the survivorship of migrating Pacific salmon, have been observed and are expected to intensify. It is not known whether these earlier, longer, and/or lower low-flows are anomalous relative to historical streamflow patterns since available gauged flow data is restricted to the last five decades. We used networks of high-elevation tree-ring data to model historical low-flow (late-summer) season streamflow regionalized across a group of hydrologically similar watersheds that were identified as susceptible to low-flow events. Our approach contrasts with typical dendrohydrological approaches in that the study watersheds are relatively small in size, and we have not employed moisture-limited tree-ring records as model predictors. In these rainfall-dominated streamflow regimes, late-summer discharge is driven by a combination of persisting snowmelt-derived inputs and variations in summer temperature. We used correlation analysis to prescreen a large pool of tree-ring chronologies as candidate model predictors, retaining those whose annual radial growth is limited by variability in those climate variables driving low-flow season discharge. We conducted principal components analysis on the retained chronologies to derive a set of tree-ring based predictors, which were entered into a stepwise multiple linear regression model to estimate historical regionalized low-flow season flows. Our model explains approximately 60% of streamflow variance, elucidates the frequencies and magnitudes of past low-flow episodes not represented within the instrumental record, and provides a historical context for contemporary shifts in the

  15. Regionalization of low flow indices in Lower Saxony

    NASA Astrophysics Data System (ADS)

    Fangmann, Anne; Haberlandt, Uwe

    2016-04-01

    For the purpose of finding an effective model to estimate low flow indices at ungauged sites within the Federal State of Lower Saxony in the north of Germany, several approaches for the regionalization of streamflow related variables are tested and evaluated. These include multiple linear regression (MLR), Ordinary Kriging (OK), External Drift Kriging (EDK) and Topological Kriging (TK). In a first preliminary step mean low flow index values are calculated for the period from 1988 to 2009 at gauges with sufficient record length. Records of smaller lengths or temporal deviation from the main period are adjusted using a simple linear regression approach with neighboring long-record stations and are weighted according to model performance. In this way, a total of 238 observed mean index values are obtained throughout the study area that serve as the target variable for all regionalization approaches tested. The first method applied to the data set is the MLR, were the target variable is modeled as a function of various physiographic catchment descriptors. Prediction performance is expected to improve through division of the study area into a set of homogeneous regions, using a k-means clustering approach and fitting an individual regression model for each region. The second set of methods tested is of geostatistical nature. The OK approach is tested by treating catchment centers as points to which the theoretical variogram is fit. The OK is extended by including the catchment descriptors selected as regressors in the MLR model as external drift variables in the EDK. The final method to be applied is the TK, a block-Kriging method accounting for both areal extent and nesting of catchments. Performances of all approaches are evaluated using a cross-validation procedure. The EDK proves as the most successful method when modeling the entire study area, but is outperformed by the MLR approach for homogeneous regions. The single MLR model for the entire study area still

  16. Low-flow sediment transport in the Colorado River

    USGS Publications Warehouse

    Gray, John R.; Webb, Robert H.; Hyndman, David W.

    1991-01-01

    In support of beach-stability research, bedload and suspended sediment were measured during a steady flow of 5,880 ft3/s and receding flows from 12,100 to 5,660 ft3/s in the Colorado River above National Canyon, near Supai, Arizona, October 7-12, 1989. During steady flows, 75 percent of the mean total-sediment discharge of 128 t/d was in suspension and about half the total-sediement load was finer than 0.062 mm. Median grain sizes of bedload and bed material were 0.43 and 0.40 mm, respecively. Although steady-flow bedload transport varied from the mean by about 45 percent, suspended-sediment discharge remained constant within sampling error. Helley-Smith and BL-86-3 bedload samplers were not significantly different. At larger transport rates, however, the rates measured by the Helley-Smith exceeded those measure by the BL-86-3. Transport rates from bedload samples collected with Helley-Smith and BL-86-3 bedload samplers in sections 8 ft apart demonstrate no consistent autocorrelation or cross correlation. Cross-sectional bedload-transport rates measured concurrently or consecutively with the bedload samplers showed good agreement indicating that bedload varied by at least a factor of 2.4 during the steady-flow period. Ninety-five percent of the bedload transport during low flow occured in the center one-third of the channel.

  17. Low-flow profiles of the Tallapoosa River and tributaries in Georgia

    USGS Publications Warehouse

    Carter, R.F.; Hopkins, E.H.; Perlman, H.A.

    1988-01-01

    Low flow information is provided for use in an evaluation of the capacity of streams to permit withdrawals or to accept waste loads without exceeding the limits of State water quality standards. The report is the fourth in a series of reports presenting the results of a low flow study of all stream basins north of the Fall Line in Georgia. This report covers the part of the Tallapoosa River basin in the Piedmont province of Georgia. The low flow characteristic presented is the minimum average flow for 7 consecutive days with a 10-year recurrence interval (7Q10). The data are presented in tables and shown graphically as ' low flow profiles ' (low flow plotted against distance along a stream channel), and as ' drainage area profiles ' (drainage area plotted against distance along a stream channel). Low flow profiles were constructed by interpolation or extrapolation from points of known low flow data. Low flow profiles are included for all stream reaches where low flow data of sufficient accuracy are available to justify computation of the profiles. Drainage area profiles are included for all stream basins > 5 sq mi, except for those in a few remote areas. Flow records were not adjusted for diversions or other factors that cause measured flows to represent conditions other than natural flow. (Author 's abstract)

  18. Which factors, processes and storages influence low flow (Q347)?

    NASA Astrophysics Data System (ADS)

    Margreth, Michael; Scherrer, Simon; Smoorenburg, Maarten; Naef, Felix

    2013-04-01

    In Switzerland, estimation of residual water is based on Q347 (flow exceeded during 347 days per year). In ungauged catchments Q347 has to be determined with some simplified approaches. However, these statistical models often provide inaccurate results. The runoff reaction of a river depends on the spatial distribution of the Dominant Runoff Processes (DRP) like Hortonian Overland Flow (HOF), Saturated Overland Flow (SOF), Sub-Surface Flow (SSF) or Deep Percolation (DP) within its catchment area. Low flow is fed by slowly reacting groundwater or deep hillslope storages. These storages are supposed to be located mainly beneath permeable soils in highly permeable bedrock like talus, deposits of debris flows or rock fall, gravel of river deposits, lateral moraines or karst systems, represented in DRP-maps by slowly reacting SOF3-, SSF3- or DP- areas. To better understand these mechanisms, the relation between areas of slowly reacting SOF3, SSF3, DP and the form of the recession curves was analysed in 27 catchments of Swiss Plateau and Jura. Results show, that drainage characteristics and percentage of SOF3-, SSF3- and DP- areas in catchments relate well. The more extended the recharge areas, the smoother and longer the recession curves. For example the recession to Q347 in the Eulach River (Area of SOF3, SSF3, DP = 54%) takes 95 days, in the Töss River only 10 days (Area of SOF3, SSF3, DP = 9%). However, the differences in Q347 cannot be explained with these percentages. The runoff volume from Q347 to Q365 in 14 investigated catchments is only between 0.2 and 14 mm, about 1.5% of the annual precipitation volume. It seems that the storages mentioned above do not contribute significantly any more, when the discharge falls below Q347. It was found that catchments with high Q347 consist mainly of sandstone, conglomerate or large scaled wetlands. It seems that mainly porous and fissured solid rocks contribute to Q347. Very small Q347 are usually caused by seepage loss of

  19. Low-flow profiles of the upper Ocmulgee and Flint rivers in Georgia

    USGS Publications Warehouse

    Carter, R.F.; Hopkins, E.H.; Perlman, H.

    1986-01-01

    This report provides low-flow information for use in evaluating the capacity of streams to supply withdrawals or to accept waste loads from potential new industries without exceeding the limits of State water-quality standards. The report is the first phase of a study of all stream basins north of the Fall Line in Georgia. It covers the Piedmont part if the Ocmulgee and Flint River basins. The low-flow characteristic presented is the minimum average flow for 7 consecutive days with a 10-year recurrence interval. The data are presented graphically as low-flow profiles (low flow as a function of distance along a stream channel) and as drainage-area profiles (drainage area as a function of distance along a stream channel). Low-flow profiles were constructed by interpolation or extrapolation from points of known low-flow data. Low-flow profiles are included for all stream reaches where low-flow data of sufficient accuracy are available to justify computation of the profiles. Drainage-area profiles are included for all stream basins larger than 5 sq mi. Flow records were not adjusted for diversions or other factors that cause measured flows to represent other than natural flow conditions. Profiles for 7-day minimum flows are omitted for stream reaches where natural flow is known to be significantly altered. (Author 's abstract)

  20. 77 FR 35464 - Extension of Comment Period-Proposed Low Flow Protection Policy

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-13

    ... From the Federal Register Online via the Government Publishing Office SUSQUEHANNA RIVER BASIN COMMISSION Extension of Comment Period--Proposed Low Flow Protection Policy AGENCY: Susquehanna River Basin... Susquehanna River Basin Commission (SRBC) extended the comment deadline for its proposed Low Flow...

  1. Low flow vortex shedding flowmeter for hypergolics/all media

    NASA Astrophysics Data System (ADS)

    Thinh, Ngo

    1990-09-01

    A family of vortex shedding flowmeters for flow measurement of hypergols that requires a long term operation without removal from system lines was further developed. A family of vortex shedding flowmeters without moving parts was designed. The test loop to evaluate the meters for the Freon flow, which simulates the hypergolic fluids, was modified and reconstructed. Preliminary results were obtained on the output frequency characteristics of an 1/2 inch flowmeter as a function of the flow rate.

  2. Low flow vortex shedding flowmeter for hypergolics/all media

    NASA Technical Reports Server (NTRS)

    Thinh, Ngo

    1990-01-01

    A family of vortex shedding flowmeters for flow measurement of hypergols that requires a long term operation without removal from system lines was further developed. A family of vortex shedding flowmeters without moving parts was designed. The test loop to evaluate the meters for the Freon flow, which simulates the hypergolic fluids, was modified and reconstructed. Preliminary results were obtained on the output frequency characteristics of an 1/2 inch flowmeter as a function of the flow rate.

  3. Low-flow characteristics of streams in the Kishwaukee River basin, Illinois

    USGS Publications Warehouse

    Allen, Howard E., Jr.; Cowan, Ellen A.

    1985-01-01

    Seven-day, 2-year, and 7-day, 10-year natural low flows are estimated at five continuous-record gaging stations based on streamflow records and records of wastewater effluent furnished by treatment plants. Low flows are also estimated at 22 partial-record stations by relating natural low-flow estimates for long-term stations to discharge measurements at partial-record stations. Standard error of estimates for the 27 gaged sites averaged 33 percent for 2-year estimates and 51 percent for 10-year estimates. A technique for estimating flows at ungaged stream sites is based on drainage area and indexes of streamflow recession. Streamflow-recession indexes were used to account for effects of geology on low flows. Multiple-regression analyses relates the low flows to drainage area and streamflow recession rates. Average standard errors of estimates of 61 and 97 percent were indicated for the 2-year and 10-year estimating equations, respectively. Wastewater treatment plant location and effluent discharged during 7-day low-flow periods in 1981 are presented for use in adjusting natural low-flow estimates at gaged and ungaged sites to represent 1981 streamflow conditions. (USGS)

  4. Estimating annual high-flow statistics and monthly and seasonal low-flow statistics for ungaged sites on streams in Alaska and conterminous basins in Canada

    USGS Publications Warehouse

    Wiley, Jeffrey B.; Curran, Janet H.

    2003-01-01

    Methods for estimating daily mean flow-duration statistics for seven regions in Alaska and low-flow frequencies for one region, southeastern Alaska, were developed from daily mean discharges for streamflow-gaging stations in Alaska and conterminous basins in Canada. The 15-, 10-, 9-, 8-, 7-, 6-, 5-, 4-, 3-, 2-, and 1-percent duration flows were computed for the October-through-September water year for 222 stations in Alaska and conterminous basins in Canada. The 98-, 95-, 90-, 85-, 80-, 70-, 60-, and 50-percent duration flows were computed for the individual months of July, August, and September for 226 stations in Alaska and conterminous basins in Canada. The 98-, 95-, 90-, 85-, 80-, 70-, 60-, and 50-percent duration flows were computed for the season July-through-September for 65 stations in southeastern Alaska. The 7-day, 10-year and 7-day, 2-year low-flow frequencies for the season July-through-September were computed for 65 stations for most of southeastern Alaska. Low-flow analyses were limited to particular months or seasons in order to omit winter low flows, when ice effects reduce the quality of the records and validity of statistical assumptions. Regression equations for estimating the selected high-flow and low-flow statistics for the selected months and seasons for ungaged sites were developed from an ordinary-least-squares regression model using basin characteristics as independent variables. Drainage area and precipitation were significant explanatory variables for high flows, and drainage area, precipitation, mean basin elevation, and area of glaciers were significant explanatory variables for low flows. The estimating equations can be used at ungaged sites in Alaska and conterminous basins in Canada where streamflow regulation, streamflow diversion, urbanization, and natural damming and releasing of water do not affect the streamflow data for the given month or season. Standard errors of estimate ranged from 15 to 56 percent for high-duration flow

  5. Comparison of low flows from the VIC hydrological model with observations for the eastern United States

    NASA Astrophysics Data System (ADS)

    Sadri, S.; Sheffield, J.

    2013-12-01

    The Variable Infiltration Capacity (VIC) model is a land surface hydrological model that simulates daily discharge flows and is used to for understanding and predicting the development and recovery of drought and its impacts, among other things. The ability of the model to accurately represent low flows is central to the development of prediction and early warning systems, as well as for decision-making for water management. In this study we compared VIC simulated streamflow over the eastern US with observed 1-day, 7-day, 30-day, and 90-day low flows, each of which has importance for a different aspect of water use, including water quality standards and reservoir operations. An initial set of 508 USGS observational sites were selected with data ranging from 1959 to 2005. We used a decomposition algorithm to identify those sites with significant step changes (detected by the Pettitt test), and significant autocorrelation (detected by the Ljung-Box test). We removed such sites from further analysis and used the remaining sites for validation of the VIC model. The number of the remaining sites for 1-day, 7-day, 30-day, and 90-day low flows were 395, 433, 453, and 467, respectively. To account for potentially different low flow dates between observations and model, a 4-month window was used for detecting the onset of the low flow periods. A hypothesis test was performed to evaluate how well the model explains the variability of observed low flows (regression analysis). Our results showed that the VIC model in its current state of calibration has the highest regression coefficient with sites that show no trends based on the Mann-Kendall test. The observed data in the northeast and the southeast of the eastern US show an increasing and decreasing trend, respectively, in the size of n-day low flows. The regression model is also consistent with the USGS land use change map over 1973-2000, which indicates deforestation in the northeast and southeast from timber harvesting

  6. Management of Low-Flow Vascular Malformations: Clinical Presentation, Classification, Patient Selection, Imaging and Treatment

    SciTech Connect

    McCafferty, Ian

    2015-10-15

    This review article aims to give an overview of the current state of imaging, patient selection, agents and techniques used in the management of low-flow vascular malformations. The review includes the current classifications for low-flow vascular malformations including the 2014 updates. Clinical presentation and assessment is covered with a detailed section on the common sclerosant agents used to treat low-flow vascular malformations, including dosing and common complications. Imaging is described with a guide to a simple stratification of the use of imaging for diagnosis and interventional techniques.

  7. Reactivity to low-flow as a potential determinant for brachial artery flow-mediated vasodilatation.

    PubMed

    Aizawa, Kunihiko; Elyas, Salim; Adingupu, Damilola D; Casanova, Francesco; Gooding, Kim M; Strain, W David; Shore, Angela C; Gates, Phillip E

    2016-06-01

    Previous studies have reported a vasoconstrictor response in the radial artery during a cuff-induced low-flow condition, but a similar low-flow condition in the brachial artery results in nonuniform reactivity. This variable reactivity to low-flow influences the subsequent flow-mediated dilatation (FMD) response following cuff-release. However, it is uncertain whether reactivity to low-flow is important in data interpretation in clinical populations and older adults. This study aimed to determine the influence of reactivity to low-flow on the magnitude of brachial artery FMD response in middle-aged and older individuals with diverse cardiovascular risk profiles. Data were analyzed from 165 individuals, divided into increased cardiovascular risk (CVR: n = 115, 85M, 67.0 ± 8.8 years) and healthy control (CTRL: n = 50, 30M, 63.2 ± 7.2 years) groups. Brachial artery diameter and blood velocity data obtained from Doppler ultrasound were used to calculate FMD, reactivity to low-flow and estimated shear rate (SR) using semiautomated edge-detection software. There was a significant association between reactivity to low-flow and FMD in overall (r = 0.261), CTRL (r = 0.410) and CVR (r = 0.189, all P < 0.05) groups. Multivariate regression analysis found that reactivity to low-flow, peak SR, and baseline diameter independently contributed to FMD along with sex, the presence of diabetes, and smoking (total R(2) = 0.450). There was a significant association between reactivity to low-flow and the subsequent FMD response in the overall dataset, and reactivity to low-flow independently contributed to FMD These findings suggest that reactivity to low-flow plays a key role in the subsequent brachial artery FMD response and is important in the interpretation of FMD data. PMID:27335431

  8. Regionalization of Low Flows in Hawaii Streams for Past and Future Rainfall Conditions

    NASA Astrophysics Data System (ADS)

    Bassiouni, M.

    2014-12-01

    The Hawaiian Islands experience large inter-annual rainfall variations and statistically significant long-term downward trends in streamflow, especially low flows, have been detected. Low flows in Hawaii streams provide a variety of beneficial uses that include maintaining fish habitat, supplying freshwater for irrigation and domestic uses, and protecting traditional and customary Hawaiian rights. However, the variability of low flows in ungaged streams in Hawaii has not been quantified and potential effects of climate change on low flows need to be better understood to properly manage surface-water resources. Regionalization of streamflow for ungaged areas in Hawaii provides a useful case study because streamflow, climate, and basin characteristics are extremely spatially and temporally variable. Here we present the development of statistical models to estimate low flows of ungaged streams in Hawaii for past and future rainfall conditions. We discuss the benefits and limitations of applying simple statistical approaches to improve understanding of changes in low flows in heterogeneous and data poor regions and to explicitly evaluate uncertainty and data needs in the context of climate change predictions for regional water-resources management.

  9. Evaluating Key Watershed Components of Low Flow Regimes in New England Streams.

    PubMed

    Morrison, Alisa C; Gold, Arthur J; Pelletier, Marguerite C

    2016-05-01

    Water resource managers seeking to optimize stream ecosystem services and abstractions of water from watersheds need an understanding of the importance of land use, physical and climatic characteristics, and hydrography on different low flow components of stream hydrographs. Within 33 USGS gaged watersheds of southern New England, we assessed relationships between watershed variables and a set of low flow parameters by using an information-theoretical approach. The key variables identified by the Akaike Information Criteria (AIC) weighting factors as generating positive relationships with low flow events included percent stratified drift, mean elevation, drainage area, and mean August precipitation. The extent of wetlands in the watershed was negatively related to low flow magnitudes. Of the various land use variables, the percentage of developed land was found to have the highest importance and a negative relationship on low flow magnitudes, but was less important than wetlands and physical and climatic features. Our results suggest that management practices aimed to sustain low flows in fluvial systems can benefit from attention to specific watershed features. We draw attention to the finding that streams located in watersheds with high proportions of wetlands may require more stringent approaches to withdrawals to sustain fluvial ecosystems during drought periods, particularly in watersheds with extensive development and limited deposits of stratified drift. PMID:27136170

  10. The impact of stormwater source-control strategies on the (low) flow regime of urban catchments.

    PubMed

    Hamel, Perrine; Fletcher, Tim D

    2014-01-01

    Stormwater management strategies increasingly recognise the need to emulate the pre-development flow regime, in addition to reducing pollutant concentrations and loads. However, it is unclear whether current design approaches for stormwater source-control techniques are effective in restoring the whole flow regime, and in particular low flows, towards their pre-development levels. We therefore modelled and compared a range of source-control stormwater management strategies, including some specifically tailored towards enhancing baseflow processes. The strategies were assessed based on the total streamflow volume and three low flow metrics. Strategies based on harvesting tanks showed much greater volume reduction than those based on raingardens. Strategies based on a low flow rate release, aimed at mimicking natural baseflow, failed to completely restore the baseflow regime. We also found that the sensitivity of the low flow metrics to the proportion of catchment treated varied amongst metrics, illustrating the importance of metrics selection in the assessment of stormwater strategies. In practice, our results suggest that realistic scenarios using low flow release from source-control techniques may not be able to fully restore the low flow regime, at least for perennial streams. However, a combination of feasibly-sized tanks and raingardens is likely to restore the baseflow regime to a great extent, while also benefitting water quality through the retention and filtration processes. PMID:24569271

  11. Low-Flow Characteristics and Discharge Profiles for Selected Streams in the Cape Fear River Basin, North Carolina, Through 1998

    USGS Publications Warehouse

    Weaver, J.C.; Pope, B.F.

    2001-01-01

    An understanding of the magnitude and frequency of low-flow discharges is an important part of evaluating surface-water resources and planning for municipal and industrial economic expansion. Low-flow characteristics are summarized in this report for 67 continuous-record gaging stations and 121 partial-record measuring sites in the Cape Fear River Basin of North Carolina. Records of discharge collected through the 1998 water year were used in the analyses. Flow characteristics included in the summary are (1) average annual unit flow; (2) 7Q10 low-flow discharge, the minimum average discharge for a 7-consecutive-day period occurring, on average, once in 10 years; (3) 30Q2 low-flow discharge; (4) W7Q10 low-flow discharge, similar to 7Q10 discharge except that only flow during November through March is considered; and (5) 7Q2 low-flow discharge. Low-flow characteristics in the Cape Fear River Basin vary widely in response to changes in geology and soil types. The area of the basin with the lowest potentials for sustained base flows is underlain by the Triassic basin in parts of Durham, Wake, and Chatham Counties. Typically, these soils are derived from basalt and fine-grained sedimentary rocks that allow very little infiltration of water into the shallow aquifers for storage and later release to streams during periods of base flow. The area of the basin with the highest base flows is the Sand Hills region in parts of Moore, Harnett, Hoke, and Cumberland Counties. Streams in the Sand Hills have the highest unit low flows in the study area as well as in much of North Carolina. Well-drained sandy soils in combination with higher topographic relief relative to other areas in the Coastal Plain contribute to the occurrence of high potentials for sustained base flows. A number of sites in the upper part of the Cape Fear River Basin underlain by the Carolina Slate Belt and Triassic basin, as well many sites in lower areas of the Coastal Plain (particularly the Northeast Cape

  12. The skill of seasonal ensemble low flow forecasts for four different hydrological models

    NASA Astrophysics Data System (ADS)

    Demirel, M. C.; Booij, M. J.; Hoekstra, A. Y.

    2014-05-01

    This paper investigates the skill of 90 day low flow forecasts using two conceptual hydrological models and two data-driven models based on Artificial Neural Networks (ANNs) for the Moselle River. One data-driven model, ANN-Indicator (ANN-I), requires historical inputs on precipitation (P), potential evapotranspiration (PET), groundwater (G) and observed discharge (Q), whereas the other data-driven model, ANN-Ensemble (ANN-E), and the two conceptual models, HBV and GR4J, use forecasted meteorological inputs (P and PET), whereby we employ ensemble seasonal meteorological forecasts. We compared low flow forecasts without any meteorological forecasts as input (ANN-I) and five different cases of seasonal meteorological forcing: (1) ensemble P and PET forecasts; (2) ensemble P forecasts and observed climate mean PET; (3) observed climate mean P and ensemble PET forecasts; (4) observed climate mean P and PET and (5) zero P and ensemble PET forecasts as input for the other three models (GR4J, HBV and ANN-E). The ensemble P and PET forecasts, each consisting of 40 members, reveal the forecast ranges due to the model inputs. The five cases are compared for a lead time of 90 days based on model output ranges, whereas the four models are compared based on their skill of low flow forecasts for varying lead times up to 90 days. Before forecasting, the hydrological models are calibrated and validated for a period of 30 and 20 years respectively. The smallest difference between calibration and validation performance is found for HBV, whereas the largest difference is found for ANN-E. From the results, it appears that all models are prone to over-predict low flows using ensemble seasonal meteorological forcing. The largest range for 90 day low flow forecasts is found for the GR4J model when using ensemble seasonal meteorological forecasts as input. GR4J, HBV and ANN-E under-predicted 90 day ahead low flows in the very dry year 2003 without precipitation data, whereas ANN

  13. Long term shift of low flows predictors in small lowland catchments of Northeast Germany

    NASA Astrophysics Data System (ADS)

    Thomas, Björn; Lischeid, Gunnar; Steidl, Jörg; Dietrich, Ottfried

    2015-02-01

    Runoff, especially during summer months, and low flows have decreased in Central and Eastern Europe during the last decades. A detailed knowledge on predictors and dependencies between meteorological forcing, catchment properties and low flow is necessary to optimize regional adaption strategies to sustain minimum runoff. The objective of this study is to identify low flow predictors for 16 small catchments in Northeast Germany and their long-term shifts between 1965 and 2006. Non-linear regression models (support vector machine regression) were calibrated to iteratively select the most powerful low flow predictors regarding annual 30-day minimum flow (AM30). The data set consists of standardized precipitation (SPI) and potential evapotranspiration (SpETI) indices on different time scales and lag times. The potential evapotranspiration of the previous 48 and 3 months, as well as the precipitation of the previous 3 months and last year were the most relevant predictors for AM30. Pearson correlation (r2) of the final model is 0.49 and if for every year the results for all catchments are averaged r2 increases to 0.80 because extremes are smoothing out. Evapotranspiration was the most important low flow predictor for the study period. However, distinct long-term shifts in the predictive power of variables became apparent. The potential evapotranspiration of the previous 48 months explained most of the variance, but its relevance decreased during the last decades. The importance of precipitation variables increased with time. Model performance was higher at catchments with a more damped discharge behavior. The results indicate changes in the relevant processes or flow paths generating low flows. The identified predictors, temporal patterns and patterns between catchments will support the development of low flow monitoring systems and determine those catchments where adaption measures should aim more at increasing groundwater recharge.

  14. Intralesional bleomycin injection in management of low flow vascular malformations in children.

    PubMed

    Mohan, Anita T; Adams, Saleigh; Adams, Kevin; Hudson, Donald A

    2015-04-01

    Low flow vascular malformations are challenging to manage, particularly with their propensity to grow, and can lead to severe disfigurement and dysfunction. Traditional surgical excision is fraught with tedious dissection and complications, particularly in the head and neck region. Trends toward less invasive techniques, such as intralesional sclerotherapy, are proving to be successful independent treatments or adjuncts in management in low flow vascular malformations. This study was a retrospective case note review, over an 8-year period, reporting the outcomes of 32 children (mean = 5.8 years, range = 5 months-11.5 years) with radiologically confirmed low flow vascular malformations, treated with serial intralesional bleomycin injection (IBI) therapy. Patient demographics, lesion characteristics, imaging findings, treatment course, radiological and clinical response to treatment were recorded. An overall 91% (n = 29) response rate was achieved, with 28% obtaining complete resolution for low flow vascular malformations. Lesions were sub-categorized into venous malformation, including mixed venous-capillary (n = 27) or lymphatic malformation (LM) (n = 5). Twenty-seven of 32 children experienced no complications. Local complications included superficial skin infection (n = 2), skin necrosis (n = 1), hyperpigmentation, and minor contour deformity. There was no recurrence and no systemic side-effects to bleomycin. Mean follow-up was 38 months (range = 6-95 months). In conclusion, serial intralesional bleomycin injections can be effective and also safe in a paediatric population for the successful management of symptomatic or disfiguring low flow vascular malformations. PMID:25204206

  15. A stream-gaging network analysis for the 7-Day, 10-year annual low flow in New Hampshire streams

    USGS Publications Warehouse

    Flynn, Robert H.

    2003-01-01

    The 7-day, 10-year (7Q10) low-flow-frequency statistic is a widely used measure of surface-water availability in New Hampshire. Regression equations and basin-characteristic digital data sets were developed to help water-resource managers determine surface-water resources during periods of low flow in New Hampshire streams. These regression equations and data sets were developed to estimate streamflow statistics for the annual and seasonal low-flow-frequency, and period-of-record and seasonal period-of-record flow durations. generalized-least-squares (GLS) regression methods were used to develop the annual 7Q10 low-flow-frequency regression equation from 60 continuous-record stream-gaging stations in New Hampshire and in neighboring States. In the regression equation, the dependent variables were the annual 7Q10 flows at the 60 stream-gaging stations. The independent (or predictor) variables were objectively selected characteristics of the drainage basins that contribute flow to those stations. In contrast to ordinary-least-squares (OLS) regression analysis, GLS-developed estimating equations account for differences in length of record and spatial correlations among the flow-frequency statistics at the various stations. A total of 93 measurable drainage-basin characteristics were candidate independent variables. On the basis of several statistical parameters that were used to evaluate which combination of basin characteristics contribute the most to the predictive power of the equations, three drainage-basin characteristics were determined to be statistically significant predictors of the annual 7Q10: (1) total drainage area, (2) mean summer stream-gaging station precipitation from 1961 to 90, and (3) average mean annual basinwide temperature from 1961 to 1990. To evaluate the effectiveness of the stream-gaging network in providing regional streamflow data for the annual 7Q10, the computer program GLSNET (generalized-least-squares NETwork) was used to analyze the

  16. Installation of a Low Flow Unit at the Abiquiu Hydroelectric Facility

    SciTech Connect

    Jack Q. Richardson

    2012-06-28

    Final Technical Report for the Recovery Act Project for the Installation of a Low Flow Unit at the Abiquiu Hydroelectric Facility. The Abiquiu hydroelectric facility existed with two each 6.9 MW vertical flow Francis turbine-generators. This project installed a new 3.1 MW horizontal flow low flow turbine-generator. The total plant flow range to capture energy and generate power increased from between 250 and 1,300 cfs to between 75 and 1,550 cfs. Fifty full time equivalent (FTE) construction jobs were created for this project - 50% (or 25 FTE) were credited to ARRA funding due to the ARRA 50% project cost match. The Abiquiu facility has increased capacity, increased efficiency and provides for an improved aquatic environment owing to installed dissolved oxygen capabilities during traditional low flow periods in the Rio Chama. A new powerhouse addition was constructed to house the new turbine-generator equipment.

  17. EFFECTS OF LOW FLOW ON INVASION PROCESS OF EXOTIC STREAM INVERTEBRATES

    NASA Astrophysics Data System (ADS)

    Yamane, Naoya; Sakai, Toru; Miyake, Yo

    This study aimed to demonstrate recent invasion status and low-flow resistance of two exotic invertebrates, Pyasa acuta and Crangonyx floridanus, in Shigenobu River, Ehime, Japan. Six years of longitudinal survey revealed that density of these two invasive species were high in the middle and lower segments of the mainstem, in which stream habitats were degraded. Furthermore, the distribution of Crangonyx floridanus appeared to expand toward upstream along the river. A short-term survey during a descending flow showed that Crangonyx floridanus decreased along with other major invertebrate taxa. In contrast, relative abundance of Pyasa acuta increased as flow decreased, indicating that this invasive species has relatively high resistance to low flow. Thus, low flow was suggested to facilitate the invasion of Pyasa acuta.

  18. Low Flows over the Eastern United States: Variability, Trends, and Attributions (1962-2011)

    NASA Astrophysics Data System (ADS)

    Kam, J.; Sheffield, J.

    2014-12-01

    Low flows are a seasonal hydrologic response generally during a drying period. Extreme low flows are a result of prolonged antecedent precipitation deficit and/or high evaporative demand, and can indicate hydrological droughts (water availability deficit) and ecological droughts (water quality degradation). Human impacts (e.g. dams, reservoirs, and power plants) also play a role in exacerbating the severity of low flow droughts. For drought mitigation, it is critical to better understand how low flows vary over time and their generating mechanisms. The goals of this study are to examine trends in low flows over the eastern U.S. and to assess their attributions and teleconnections in the context of climate change and variability. We selected 149 out of 4878 USGS stations over the eastern U.S., taking into account data availability and minimal human impacts. We analyzed annual 7-day low flows (Q7) from the series of daily streamflow records for 1962-2011. We also computed an antecedent precipitation (AP) over the corresponding basin for each station. We found a north-south (increasing-decreasing) dipole pattern in Q7 trends and a monopole (increasing) pattern in AP trends, which indicates a gap between the trends of Q7 and AP over the southern part of the study region (Virginia, North and South Carolina). We found that these regions show significant increasing trends in potential evapotranspiration (PET) as driven by increasing temperatures and vapor pressure deficit. We also examined teleconnections between detrended Q7 and nine atmospheric and oceanic climate indices. We found that the North Atlantic Oscillation (NAO) and Pacific North America (PNA) pattern show prediction skill for Q7 at one and two month lead time, respectively. Our findings suggest that the worst scenario for future droughts over the eastern U.S. is a combination of a response to an increasing trend in temperature driving PET with strong negative NAO and positve PNA during summer.

  19. Case Report: Conversion of a Low-Flow to High-Flow Priapism

    PubMed Central

    Cahn, David; Courter, Elliot; Diorio, Gregory; Metro, Michael; Ginsberg, Phillip

    2015-01-01

    Priapism is defined as an erection lasting for more than 4 hours and can be grouped into 3 distinct subtypes: ischemic (low-flow), stuttering and non-ischemic (high-flow). Herein, we present an interesting case of conversion from a low-flow to high-flow priapism after a distal shunting procedure. This is a rare phenomenon that has a paucity of documented cases. Diagnosis requires prompt clinical suspicion and confirmatory testing including penile cavernosal blood gases and Doppler ultrasound. PMID:26889126

  20. Influence of objective function selection on modeling high and low flows in a changing climate

    NASA Astrophysics Data System (ADS)

    Vaze, J.; Petheram, C.; Chiew, F. H.; Teng, J.; Wang, B.; Post, D. A.

    2012-12-01

    This study evaluates the ability of commonly used hydrological models at simulating streamflow under variable climate conditions for different streamflow characteristics. The models are calibrated using three objective functions that weight high and low flow characteristics differently. The models are calibrated using data from ten unregulated catchments in southeast Australia. The results show that when the GR4J model is calibrated against low flows, it performs better in simulating low flows over an independent period compared to the simulation when using a high-flow objective function but this improvement in simulating low flows comes at the cost of poor simulations of high flows. The simulation results for the Sacramento model are different to GR4J and show that the Sacramento model calibrated specifically against low flows does not necessarily perform better in simulating low flows for an independent period not used in model calibration. The results for the two models also show that a model calibrated specifically against low flows does not necessarily perform better in simulating the bias of the lower 30% of fdc for an independent period not used in model calibration. The simulation results for both of the models indicate that model parameters calibrated using an objective function which gives more weight to high and medium flows are suitable for simulating streamflow for an independent period with reasonably high daily NSE values. The results also show that objective functions which puts more weight on low flows or similar weight to all flows is not suitable for simulating streamflow for an independent period if the metric of interest is daily NSE. The simulation-bias results indicate that there is no clear under or overestimation of flows when model parameters calibrated against wet or dry periods are used to simulate streamflow for an independent dry or wet period. The overall results from this study indicate that there is no single objective function that

  1. Effects of Surficial Geology, Lakes and Swamps, and Annual Water Availability on Low Flows of Streams in Central New England, and Their Use of Low-Flow Estimation

    USGS Publications Warehouse

    Wandle, S. William, Jr.; Randall, Allan D.

    1994-01-01

    Equations developed by multiple-regression analysis of data from 49 drainage basins in Massachusetts, New Hampshire, Rhode Island, Vermont, and southwestern Maine indicate that low flow of streams in this region is largely a function of the amount of water available to the basin and the extent of surficial sand and gravel relative to the extent of till and fine-grained stratified drift. Low flow per square mile from areas of surficial sand and gravel is consistently much greater than that from areas of till and bedrock, but flood plains and alluvial fans seem to contribute less low flow per square mile than do other types of surficial sand and gravel. The areal extent of lakes and swamps also correlates negatively with low flow in multiple-regression equations, presumably because intense evapotranspiration from these localities consumes water that would otherwise become streamflow. The annual minimum 7-day mean low flows that occur during summer and fall at 2-year and 10-year recurrence intervals (7Q2 and 7QIO) were selected as indices of low flow and were adjusted to a common base period, 1942-71. Central New England was divided into a region of high relief that com- prises much of New Hampshire, Vermont, and western Massachusetts, and a region of low relief that generally lies to the east and south but also includes the Lake Champlain lowland of Vermont. In the high-relief region, mean basin elevation proved to be the most significant index of the amount of water available. In the low-relief region, mean annual runoff per square mile was more significant than elevation, particularly when multiplied by the areal extent of sand and gravel and that of till. Dividing the areal extent of sand and gravel by stream length improved the fit of regression equations for the low-relief region. Regression equations were developed that explained at least 95 percent of the variation in 7QIO within both the high-relief and the low-relief data sets. Equations proposed for

  2. Influences of North Atlantic climate variability on low-flows in the Connecticut River Basin

    NASA Astrophysics Data System (ADS)

    Steinschneider, Scott; Brown, Casey

    2011-10-01

    SummaryConnections between summertime, ecologically relevant low-flow indicators and both winter and spring climate phenomena are explored for the Connecticut River Basin, with an emphasis on assessing forecast potential. Low-flow streamflow statistics deemed important for ecological health, including minimum 1-day mean flows, minimum 7-day mean flows, and monthly streamflow averages from June to September, are derived from 61 years of continuous, daily streamflow data at 15 United States Geological Survey streamflow gauging stations across the basin. Relationships between the ecological flow indicators with leading sea-surface temperature and sea-level pressure are investigated using correlation and composite analysis. Results suggest lagged relationships of up to 5 months between summer streamflow and the wintertime North Atlantic Oscillation, springtime east coast pressure trough, and springtime North Atlantic Tripole. These climate states have been linked to shifts between zonal and meridonal airflow as well as sea-surface temperature anomalies off the coast of the eastern US, both of which have implications for the movement of moisture systems over the study region. This study suggests that residual influences on airflow and sea-surface temperature persist into the summer following these earlier climate states, influencing low-flow hydrology in the region. As eco-hydrologic flow targets often conflict with other stakeholder objectives within a watershed, reservoir operators may utilize such lagged teleconnection patterns to predict annual low-flow characteristics in the region and help negotiate tradeoffs between traditional water management objectives and those emphasizing ecological conservation.

  3. SURVEY OF LOW FLOW DRAINAGES AND SEEPS IN COLORADO TO ASSESS IMPLEMENTABILITY OF PASSIVE TREATMENT OPTIONS

    EPA Science Inventory

    Low flow drainages and seeps are typically not evaluated for mitigation due to the perceived low impact on the watershed. However, localized metals concentrations and acidity can be at levels of concern. Future passage of a “Good Samaritan Act” should increase activity at curren...

  4. DIEL DISSOLVED OXYGEN MONITORING OF THE SPOKANE RIVER DURING EXTREME LOW FLOW. KOOTENAI COUNTY, IDAHO, 1992

    EPA Science Inventory

    Diel monitoring of dissolved oxygen and temperature was conducted on an impounded and free-flowing reach of the Spokane River, in north Idaho (17010303) on 2 occasions during an extreme low flow event in water year 1992. The objective was to document excursions from water qualit...

  5. NOVEL CERAMIC MEMBRANE BIOREACTOR FOR LOW-FLOW SYSTEMS - PHASE I

    EPA Science Inventory

    Improved low-flow (50,000 gallons per day) sanitary wastewater treatment systems are needed. CeraMem Corporation's proposed approach includes a membrane bioreactor (MBR) using fully proven biological processes for biological oxygen demand oxidation and (optionally) fo...

  6. Effects of Low-Flow Sevoflurane Anesthesia on Pulmonary Functions in Patients Undergoing Laparoscopic Abdominal Surgery.

    PubMed

    Doger, Cihan; Kahveci, Kadriye; Ornek, Dilsen; But, Abdulkadir; Aksoy, Mustafa; Gokcinar, Derya; Katar, Didem

    2016-01-01

    Objective. The aim of this prospective, randomized study was to investigate the effects of low-flow sevoflurane anesthesia on the pulmonary functions in patients undergoing laparoscopic cholecystectomy. Methods. Sixty American Society of Anesthesiologists (ASA) physical status classes I and II patients scheduled for elective laparoscopic cholecystectomy were included in the study. Patients were randomly allocated to two study groups: high-flow sevoflurane anesthesia group (Group H, n = 30) and low-flow sevoflurane anesthesia group (Group L, n = 30). The fresh gas flow rate was of 4 L/min in high-flow sevoflurane anesthesia group and 1 L/min in low-flow sevoflurane anesthesia group. Heart rate (HR), mean arterial blood pressure (MABP), peripheral oxygen saturation (SpO2), and end-tidal carbon dioxide concentration (ETCO2) were recorded. Pulmonary function tests were performed before and 2, 8, and 24 hours after surgery. Results. There was no significant difference between the two groups in terms of HR, MABP, SpO2, and ETCO2. Pulmonary function test results were similar in both groups at all measurement times. Conclusions. The effects of low-flow sevoflurane anesthesia on pulmonary functions are comparable to high-flow sevoflurane anesthesia in patients undergoing laparoscopic cholecystectomy. PMID:27413741

  7. GROUND WATER ISSUE: LOW-FLOW (MINIMAL DRAWDOWN) GROUND-WATER SAMPLING PROCEDURES

    EPA Science Inventory

    This paper is intended to provide background information on the development of low-flow sampling procedures and its application under a variety of hydrogeologic settings. The sampling methodology described in this paper assumes that the monitoring goal is to sample monitoring wel...

  8. Effects of Low-Flow Sevoflurane Anesthesia on Pulmonary Functions in Patients Undergoing Laparoscopic Abdominal Surgery

    PubMed Central

    Doger, Cihan; Kahveci, Kadriye; Ornek, Dilsen; But, Abdulkadir; Aksoy, Mustafa; Gokcinar, Derya; Katar, Didem

    2016-01-01

    Objective. The aim of this prospective, randomized study was to investigate the effects of low-flow sevoflurane anesthesia on the pulmonary functions in patients undergoing laparoscopic cholecystectomy. Methods. Sixty American Society of Anesthesiologists (ASA) physical status classes I and II patients scheduled for elective laparoscopic cholecystectomy were included in the study. Patients were randomly allocated to two study groups: high-flow sevoflurane anesthesia group (Group H, n = 30) and low-flow sevoflurane anesthesia group (Group L, n = 30). The fresh gas flow rate was of 4 L/min in high-flow sevoflurane anesthesia group and 1 L/min in low-flow sevoflurane anesthesia group. Heart rate (HR), mean arterial blood pressure (MABP), peripheral oxygen saturation (SpO2), and end-tidal carbon dioxide concentration (ETCO2) were recorded. Pulmonary function tests were performed before and 2, 8, and 24 hours after surgery. Results. There was no significant difference between the two groups in terms of HR, MABP, SpO2, and ETCO2. Pulmonary function test results were similar in both groups at all measurement times. Conclusions. The effects of low-flow sevoflurane anesthesia on pulmonary functions are comparable to high-flow sevoflurane anesthesia in patients undergoing laparoscopic cholecystectomy. PMID:27413741

  9. High performance in low-flow solar domestic hot water systems

    SciTech Connect

    Dayan, M.

    1997-12-31

    Low-flow solar hot water heating systems employ flow rates on the order of 1/5 to 1/10 of the conventional flow. Low-flow systems are of interest because the reduced flow rate allows smaller diameter tubing, which is less costly to install. Further, low-flow systems result in increased tank stratification. Lower collector inlet temperatures are achieved through stratification and the useful energy produced by the collector is increased. The disadvantage of low-flow systems is the collector heat removal factor decreases with decreasing flow rate. Many solar domestic hot water systems require an auxiliary electric source to operate a pump in order to circulate fluid through the solar collector. A photovoltaic driven pump can be used to replace the standard electrical pump. PV driven pumps provide an ideal means of controlling the flow rate, as pumps will only circulate fluid when there is sufficient radiation. Peak performance was always found to occur when the heat exchanger tank-side flow rate was approximately equal to the average load flow rate. For low collector-side flow rates, a small deviation from the optimum flow rate will dramatically effect system performance.

  10. Importance of seasonal snowpack for summer low flows in humid catchments

    NASA Astrophysics Data System (ADS)

    Jenicek, Michal; Seibert, Jan; Zappa, Massimiliano; Staudinger, Maria; Jonas, Tobias

    2016-04-01

    The expected increase of air temperature will increase the ratio of liquid to solid precipitation during the cold season and, thus decrease the amount of snow storage, especially in mid-elevation mountain ranges across Europe. The decrease of snow will affect soil and groundwater storages during spring and might cause low streamflow values in the subsequent warm season. To evaluate these potential climate change impacts, we investigated the effects of inter-annual variations in snow accumulation on summer low flow. We worked towards 1) quantifying how long snowmelt affects runoff after melt-out and 2) estimating the sensitivity of catchments with different elevation ranges to changes in snowpack. To find suitable predictors of summer low flow we used long time series from 14 alpine and pre-alpine catchments in Switzerland and computed different variables quantifying winter and spring snow conditions. In general, the results indicated that maximum winter snow water equivalent (SWE) influenced summer low flow, but could expectedly only partly explain the observed inter-annual variations. On average, every decrease of maximum SWE by 10% caused a decrease of minimum discharge in July by 6% to 9% in catchments higher than 2000 m a.s.l. This effect is reduced in middle and lower elevation catchments (a decrease of minimum discharge by 2-5% per 10% decrease of maximum SWE). For higher and middle elevation catchments and years with below-average SWE maximum, the minimum discharge in July decreased to 70-90% of its normal level. Additionally, a reduction in SWE resulted in earlier low flow occurrence. One other important factor was the precipitation between maximum SWE and summer low flow. When only dry preceding conditions in this period were considered, the importance of maximum SWE as a predictor of low flows increased. We assessed the sensitivity of individual catchments to the change of maximum SWE using the non-parametric Theil-Sen approach as well as an elasticity

  11. Defining the sources of low-flow phosphorus transfers in complex catchments.

    PubMed

    Arnscheidt, J; Jordan, P; Li, S; McCormick, S; McFaul, R; McGrogan, H J; Neal, M; Sims, J T

    2007-08-15

    Nutrient transfers from the land to rivers have the potential to cause persistent eutrophic impacts at low flows even though the transfers may constitute a minor percentage of total annual fluxes. In rural catchments, the contribution from agricultural soils during storm events can be particularly large and untangling the relative contributions from multiple sources that vary in time and space is especially problematic. In this study, the potential for domestic septic tank system pollution during low flows was investigated in 3 small catchments (3 to 5 km(2)) using an integrated series of methods. These included septic system surveys, continuous (10 min) total phosphorus (TP) monitoring at the outlet of each catchment, repeated low-flow water quality surveys in sub-catchments upstream of the catchment outlets and single day river-walk water quality surveys. A series of faecal matter and grey-water fingerprinting techniques were also employed. These included determining sterol ratios in stream sediments, monitoring the presence of proteins, E. coli and enterococci bacterial signatures and boron. The total density and density of poorly maintained septic systems mirrored the magnitude of frequent TP concentrations in the catchments although this relationship was less apparent in the nested sub-catchments. The exception was possibly related to the simple hydraulics in one particular catchment and indicated temporary effluent attenuation in the other catchments. Repeated low-flow and river-walk water quality surveys highlighted discrete areas and reaches where stepped changes in nutrient concentration occurred. Bio-chemical fingerprinting showed that between 7% and 27% of sediments were contaminated with human faecal material and correlation matrices indicated that, at least during low flows, P fractions were positively correlated with some markers of faecal and grey-water contamination. PMID:17512972

  12. Post-processing of a low-flow forecasting system in the Thur basin (Switzerland)

    NASA Astrophysics Data System (ADS)

    Bogner, Konrad; Joerg-Hess, Stefanie; Bernhard, Luzi; Zappa, Massimiliano

    2015-04-01

    Low-flows and droughts are natural hazards with potentially severe impacts and economic loss or damage in a number of environmental and socio-economic sectors. As droughts develop slowly there is time to prepare and pre-empt some of these impacts. Real-time information and forecasting of a drought situation can therefore be an effective component of drought management. Although Switzerland has traditionally been more concerned with problems related to floods, in recent years some unprecedented low-flow situations have been experienced. Driven by the climate change debate a drought information platform has been developed to guide water resources management during situations where water resources drop below critical low-flow levels characterised by the indices duration (time between onset and offset), severity (cumulative water deficit) and magnitude (severity/duration). However to gain maximum benefit from such an information system it is essential to remove the bias from the meteorological forecast, to derive optimal estimates of the initial conditions, and to post-process the stream-flow forecasts. Quantile mapping methods for pre-processing the meteorological forecasts and improved data assimilation methods of snow measurements, which accounts for much of the seasonal stream-flow predictability for the majority of the basins in Switzerland, have been tested previously. The objective of this study is the testing of post-processing methods in order to remove bias and dispersion errors and to derive the predictive uncertainty of a calibrated low-flow forecast system. Therefore various stream-flow error correction methods with different degrees of complexity have been applied and combined with the Hydrological Uncertainty Processor (HUP) in order to minimise the differences between the observations and model predictions and to derive posterior probabilities. The complexity of the analysed error correction methods ranges from simple AR(1) models to methods including

  13. Sevoflurane in low-flow anesthesia using “equilibration point”

    PubMed Central

    Chatrath, Veena; Khetarpal, Ranjana; Bansal, Divya; Kaur, Harjinder

    2016-01-01

    Context: While giving low-flow anesthesia, it is a routine practice to give fixed duration of initial high-flow. This study was conducted to show the use of equilibration point as changeover point from initial high-flow to low-flow. Aims: It was to compare the use of equilibration point, hemodynamics, end-tidal agent concentration, recovery time, and recovery score between isoflurane and sevoflurane. Settings and Design: It was a prospective randomized study conducted on 100 patients who were admitted for elective surgery expected to be < 2 h duration. Materials and Methods: Patients were randomly assigned to one of the two groups of 50 each. Group I received isoflurane and Group S sevoflurane as an inhalational agent. Statistical Analysis: The observations obtained in both the groups were recorded and compared. Analysis was done using unpaired t-test and Chi-square test. Results: Hemodynamic parameters were comparable in both the groups. The mean equilibration times obtained for sevoflurane and isoflurane were 8.22 ± 1.060 min and 17.24 ± 10.2 min, respectively. The drift in end-tidal agent concentration over time was less in sevoflurane group. Mean recovery time was 7.92 ± 1.56 min in the sevoflurane group and 12.89 ± 3.45 min in the isoflurane group (P = 0.001). There was no significant difference between intraoperative and postoperative complications. Conclusion: Use of equilibration time of the volatile anesthetic agent as a changeover point, from high-flow to low-flow, can help us to use circle system with low-flow anesthesia in a more efficient way, especially with newer anesthetics such as sevoflurane. PMID:27212762

  14. Postoperative Low-Flow Cerebrospinal Fluid Leak of Endoscopic Endonasal Transsphenoidal Surgery for Pituitary Adenoma

    PubMed Central

    Zhan, Rucai; Chen, Songyu; Xu, Shujun; Liu, James K.; Li, Xingang

    2015-01-01

    Abstract To assess the effectiveness of continuous lumbar drainage (LD) for management of postoperative cerebrospinal fluid leaks after endoscopic endonasal transsphenoidal approach for resection of pituitary adenoma. Three hundred eighty-four medical records of patients who were admitted to our institute during a 2.5-year period were retrospectively reviewed, 33 of them experienced low-flow cerebrospinal fluid leak postoperatively. If LD was used, all patients with low-flow cerebrospinal fluid leak were classified into 2 groups, lumbar drained group and conservatively treated group. The age, sex, management of cerebrospinal fluid leaks, and related complications were reviewed. Statistical comparisons between the 2 groups were made using SPSS 19.0 (IBM Corp, Armonk, NY). The differences were considered statistically significant if the P value was less than 0.05. Thirty-three of 384 (8.6%) experienced low-flow postoperative cerebrospinal fluid leaks. Cured rate of cerebrospinal fluid leak was 94.4% (17/18) in continuous lumbar drained group, and 93.3% (14/15) in control group. There were 2 (11.2%) patients who developed meningitis in the LD group and 1 (5.6%) patient in the control group. One patient required endoscopic repair of skull base because of persistent cerebrospinal fluid leak in both groups, with the rates of 5.6% and 6.7%, respectively. There was no significant difference noted in each rate in both groups. Placement of LD may not be necessary for the management of low-flow postoperative cerebrospinal fluid leak after using endoscopic endonasal transsphenoidal approach to pituitary adenoma. PMID:26080170

  15. Low flow venous malformation lesion presented with medial canthal swelling simulating swelling of the lacrimal sac origin: A case report

    PubMed Central

    ALSwaina, Nayef F.; ALSuhaibani, Adel H.

    2015-01-01

    Low flow venous malformation lesions (e.g. cavernous venous malformations) are commonly seen in the orbit and peri-orbital area. Common conditions may present with unexpected presentation. Here we report a 50 years old male patient with low flow venous malformation lesion presented with medial canthal swelling similar to the swelling typically seen in lacrimal sac related pathologies. PMID:26309438

  16. What can we learn about low flow storage properties from flow duration curves?

    NASA Astrophysics Data System (ADS)

    Floriancic, Marius; Margreth, Michael; Naef, Felix

    2016-04-01

    Flow duration curves are widely used for quantifying recurrence magnitude of streamflow and are of major importance for predicting low flows (Q95) in gauged catchments. But which physical hillslope properties describe the course of duration curves? And how can we derive duration curves for ungauged catchments? We show the influence of dominant runoff processes - the storage and drainage capacity of soils - and short term storage of the upper layer on flow duration curves. Catchments inhabiting large storage have different duration curves than catchments with small storage. But dominant runoff process maps cannot fully capture the influence of those storage features. For low flow prediction, other mechanisms are prevalent. We found two main gradients in duration curves from numerous catchments in the Swiss midlands and Alps: a steeper part from Q1 to approximately Q65 and a flatter part from Q65 to Q100. We propose that duration curves can be reconstructed by comparing the storage settings of gauged reference areas to ungauged catchments. The steeper part until Q65 can be reconstructed by gathered knowledge on dominant runoff processes, gradient of the flatter part by two discharge measurements at a defined time between Q65 to Q100. This simple approach can help improving low flow estimations in ungauged areas, based on physical assumptions on storage properties in reference areas.

  17. Effectiveness of low flow vascular lesions sclerosis with monoethanolamine: report of six cases.

    PubMed

    Bonan, Paulo Rogério Ferreti; Miranda, Leonardo de Paula; Mendes, Danilo Cangussu; de Paula, Alfredo Maurício Batista; Pego, Sabina Pena Borges; Martelli-Júnior, Hercílio

    2007-12-01

    Vascular malformations or even hemangiomas need therapeutic intervention if they start to cause clinical symptoms or personal discomfort. Different therapeutic modalities, including cryotherapy, corticosteroids, laser therapy, sclerotherapy, surgery, and/or embolization, can be performed successfully. Sclerotherapy with monoethanolamine is a relatively simple and effective method to treat low flow vascular lesions. We presented a report of six cases of vascular malformations treated with monoethanolamine. There were 3 male and 3 female patients, with an age range of 20 to 68 years. The patients were submitted to applications according to clinical response and/or tolerability. In all cases, low-flow vascular lesions were recorded and submitted to infiltration with 2.5% monoethanolamine, directly into the lesions. The volume applied was approximately the middle of affected area. Vascular lesions were characterized as low-flow due to absence of arterial pulsation and flat consistence. The sclerosis with 2.5% monoethanolamine resulted in complete or partial involution, without severe complications. PMID:17978777

  18. Geologic Controls on Channel Morphology and Low-Flow Habitat; Rattlesnake Creek, Santa Barbara, California

    NASA Astrophysics Data System (ADS)

    Bean, G.; Keller, E.

    2006-12-01

    Channel morphology and baseflow are limiting factors in sustaining low-flow habitat for the spawning and rearing of endangered southern steelhead trout in southern California. To aid the recovery of steelhead trout, it is imperative to determine how pools are formed and maintained in steep mountain streams, and what hydrogeologic factors control baseflow. Rattlesnake Creek, a steep (6 to 31%) boulder-bedrock channel in Santa Barbara, California, was investigated to determine if geologic and hydrogeologic properties, specifically rock strength and fracture density, control channel morphology and low-flow habitat. Analysis of rock strength, fracture density, and channel morphology using a single-factor analysis of variance, Kolmorgorov-Smirnov test and t-test suggest that rock strength and fracture density of the underlying lithology (bed and banks) does not significantly affect the channel morphology at the 0.05 level of significance. However, this study does show that boulder large roughness elements (LREs) armor the channel, controlling channel gradient and the location, abundance and type of pools. Step pools are the dominant pool type, found in reaches up to 18% where cascades might be expected, and steps are composed of resistant sandstone boulder LREs. Although fracture density does not influence the morphology of the channel, baseflow for low-flow habitat is predominantly supplied through fractures in the coldwater sandstone.

  19. Ensemble reconstruction of severe low flow events in France since 1871

    NASA Astrophysics Data System (ADS)

    Caillouet, Laurie; Vidal, Jean-Philippe; Sauquet, Eric; Devers, Alexandre; Graff, Benjamin

    2016-04-01

    This work presents a study of severe low flow events that occurred from 1871 onwards for a large number of near-natural catchments in France. It aims at assessing and comparing their characteristics to improve our knowledge on historical events and to provide a selection of benchmark events for climate change adaptation purposes. The historical depth of streamflow observations is generally limited to the last 50 years and therefore offers too small a sample of severe low flow events to properly explore the long-term evolution of their characteristics and associated impacts. In order to overcome this limit, this work takes advantage of a 140-year ensemble hydrometeorological dataset over France based on: (1) a probabilistic precipitation and temperature downscaling of the Twentieth Century Reanalysis over France (Caillouet et al., 2015), and (2) a continuous hydrological modelling that uses the high-resolution meteorological reconstructions as forcings over the whole period. This dataset provides an ensemble of 25 equally plausible daily streamflow time series for a reference network of stations in France over the whole 1871-2012 period. Severe low flow events are identified based on a combination of a fixed threshold and a daily variable threshold. Each event is characterized by its deficit, duration and timing by applying the Sequent Peak Algorithm. The procedure is applied to the 25 simulated time series as well as to the observed time series in order to compare observed and simulated events over the recent period, and to characterize in a probabilistic way unrecorded historical events. The ensemble aspect of the reconstruction leads to address specific issues, for properly defining events across ensemble simulations, as well as for adequately comparing the simulated characteristics to the observed ones. This study brings forward the outstanding 1921 and 1940s events but also older and less known ones that occurred during the last decade of the 19th century. For

  20. Hierarchy of climate and hydrological uncertainties in transient low flow projections

    NASA Astrophysics Data System (ADS)

    Vidal, J.-P.; Hingray, B.; Magand, C.; Sauquet, E.; Ducharne, A.

    2015-12-01

    This paper proposes a methodology for estimating the transient probability distribution of yearly hydrological variables conditional to an ensemble of projections built from multiple general circulation models (GCMs), multiple statistical downscaling methods (SDMs) and multiple hydrological models (HMs). The methodology is based on the quasi-ergodic analysis of variance (QE-ANOVA) framework that allows quantifying the contributions of the different sources of total uncertainty, by critically taking account of large-scale internal variability stemming from the transient evolution of multiple GCM runs, and of small-scale internal variability derived from multiple realizations of stochastic SDMs. The QE-ANOVA framework was initially developed for long-term climate averages and is here extended jointly to (1) yearly anomalies and (2) low flow variables. It is applied to better understand possible transient futures of both winter and summer low flows for two snow-influenced catchments in the southern French Alps. The analysis takes advantage of a very large dataset of transient hydrological projections that combines in a comprehensive way 11 runs from 4 different GCMs, 3 SDMs with 10 stochastic realizations each, as well as 6 diverse HMs. The change signal is a decrease in yearly low flows of around -20 % in 2065, except for the most elevated catchment in winter where low flows barely decrease. This signal is largely masked by both large- and small-scale internal variability, even in 2065. The time of emergence of the change signal on 30 year low-flow averages is however around 2035, i.e. for time slices starting in 2020. The most striking result is that a large part of the total uncertainty - and a higher one than that due to the GCMs - stems from the difference in HM responses. An analysis of the origin of this substantial divergence in HM responses for both catchments and in both seasons suggests that both evapotranspiration and snowpack components of HMs should be

  1. Low-flow characteristics of the Mississippi River upstream from the Twin Cities Metropolitan Area, Minnesota, 1932-2007

    USGS Publications Warehouse

    Kessler, Erich; Lorenz, David L.

    2010-01-01

    The U.S. Geological Survey, in cooperation with the Metropolitan Council, conducted a study to characterize regional low flows during 1932?2007 in the Mississippi River upstream from the Twin Cities metropolitan area in Minnesota and to describe the low-flow profile of the Mississippi River between the confluence of the Crow River and St. Anthony Falls. Probabilities of extremely low flow were estimated for the streamflow-gaging station (Mississippi River near Anoka) and the coincidence of low-flow periods, defined as the extended periods (at least 7 days) when all the daily flows were less than the 10th percentile of daily mean flows for the entire period of record, at four selected streamflow-gaging stations located upstream. The likelihood of extremely low flows was estimated by a superposition method for the Mississippi River near Anoka that created 5,776 synthetic hydrographs resulting in a minimum synthetic low flow of 398 cubic feet per second at a probability of occurrence of 0.0002 per year. Low-flow conditions at the Mississippi River above Anoka were associated with low-flow conditions at two or fewer of four upstream streamflow-gaging stations 42 percent of the time, indicating that sufficient water is available within the basin for many low flows and the occurrence of extremely low-flows is small. However, summer low-flow conditions at the Mississippi River above Anoka were almost always associated with low-stage elevations in three or more of the six upper basin reservoirs. A low-flow profile of the Mississippi River between the confluence of the Crow River and St. Anthony Falls was completed using a real-time kinematic global positioning system, and the water-surface profile was mapped during October 8?9, 2008, and annotated with local landmarks. This was done so that water-use planners could relate free-board elevations of selected water utility structures to the lowest flow conditions during 2008.

  2. UMTRA ground water sampling techniques: Comparison of the traditional and low flow methods

    SciTech Connect

    1995-07-01

    This report describes the potential changes in water quality data that may occur with the conversion from MBV (multiple bore volume) to LF (low flow) sampling and provides two examples of how such a change might impact Project decisions. The existing scientific literature on LF sampling is reviewed and the new LF data from three UMTRA Uranium Mill Tailings Remedial Action Project sites are evaluated seeking answers to the questions posed above. Several possible approaches, that the UMTRA Project may take to address issues unanswered by the literature are presented and compared, and a recommendation is offered for the future direction of the LF conversion effort.

  3. A scenario neutral approach to assess low flow sensitivity to climate change

    NASA Astrophysics Data System (ADS)

    Sauquet, Eric; Prudhomme, Christel

    2015-04-01

    Most impact studies of climate change on river flow regime are performed following top-down approaches, where changes in hydrological characteristics are obtained from rainfall-runoff models forced by downscaled projections provided by GCMs. However, such approaches are not always considered robust enough to bridge the gap between climate research and stake holders needs to develop relevant adaptation strategy (Wilby et al., 2014). Alternatively, 'bottom-up' approaches can be applied to climate change impact studies on water resources to assess the intrinsic vulnerability of the catchments and ultimately help to prioritize adaptation actions for areas highly sensitive to small deviations from the present-day climate conditions. A general framework combining the scenario-neutral methodology developed by Prudhomme et al. (2010) and climate elasticity analyses (Sankarasubramanian et al., 2001) is presented and applied to measure the vulnerability of low flows and droughts on a large dataset of more than 400 French gauged basins. The different steps involved in the suggested framework are: - Calibration of the GR5J rainfall runoff model (Pushpalatha et al., 2011) against observations, - Identification of the main climate factors influencing low flows, - Definition of the sensitivity domain for precipitation (P), temperature (T) and potential evapotranspiration (PE) scenarios consistent with most recent climate change projections, - Derivation of the response surface describing changes in low flow and drought regime in terms of severity, duration and seasonality (Catalogne, 2012), - Uncertainty assessment. Results are the basis for a classification of river basins according to their sensitivity at national scale and for discussions on adaptation requirements with stakeholders. Catalogne C (2012) Amélioration des méthodes de prédétermination des débits de référence d'étiage en sites peu ou pas jaugés. PHD thesis, Université Joseph Fourier, Grenoble, 285 pp

  4. Simulations of inducers at Low-Flow Off-Design Conditions

    NASA Technical Reports Server (NTRS)

    Hosangadi, Ashvin; Ahuja, Vineet; Ungewitter, Ronald J.

    2005-01-01

    The ability to accurately model details of inlet back flow for inducers operating at low-flow, off-design conditions is evaluated. A sub-scale version of a three- bladed liquid hydrogen inducer tested in water with detailed velocity and pressure measurements is used as a numerical test bed. Under low-flow, off-design conditions the length of the separation zone as well as the swirl velocity magnitude was under predicted with a standard k-E model. When the turbulent viscosity coefficient was reduced good comparison was obtained at all the flow conditions examined with both the magnitude and shape of the profile matching well with the experimental data taken half a diameter upstream of the leading edge. The velocity profiles and incidence angles at the leading edge itself were less sensitive to the back flow length predictions indicating that single-phase performance predictions may be well predicted even if the details of flow separation modeled are incorrect. However, for cavitating flow situations the prediction of the correct swirl in the back flow and the pressure depression in the core becomes critical since it leads to vapor formation. The simulations have been performed using the CRUNCH CFD@ code that has a generalized multi-element unstructured framework and an advanced multi-phase formulation for cryogenic fluids. The framework has been validated rigorously for predictions of temperature and pressure depression in cryogenic fluid cavities and has also been shown to predict the cavitation breakdown point for inducers at design conditions.

  5. Design and experimental study of high-speed low-flow-rate centrifugal compressors

    SciTech Connect

    Gui, F.; Reinarts, T.R.; Scaringe, R.P.; Gottschlich, J.M.

    1995-12-31

    This paper describes a design and experimental effort to develop small centrifugal compressors for aircraft air cycle cooling systems and small vapor compression refrigeration systems (20--100 tons). Efficiency improvements at 25% are desired over current designs. Although centrifugal compressors possess excellent performance at high flow rates, low-flow-rate compressors do not have acceptable performance when designed using current approaches. The new compressors must be designed to operate at a high rotating speed to retain efficiency. The emergence of the magnetic bearing provides the possibility of developing such compressors that run at speeds several times higher than current dominating speeds. Several low-flow-rate centrifugal compressors, featured with three-dimensional blades, have been designed, manufactured and tested in this study. An experimental investigation of compressor flow characteristics and efficiency has been conducted to explore a theory for mini-centrifugal compressors. The effects of the overall impeller configuration, number of blades, and the rotational speed on compressor flow curve and efficiency have been studied. Efficiencies as high as 84% were obtained. The experimental results indicate that the current theory can still be used as a guide, but further development for the design of mini-centrifugal compressors is required.

  6. What are the governing processes during low-flows in a chalk catchment?

    NASA Astrophysics Data System (ADS)

    Lubega Musuuza, Jude; Coxon, Gemma; Hutton, Chris; Howden, Nicholas; Woods, Ross; Freer, Jim; Wagener, Thorsten

    2016-04-01

    Low flows are important because they lead to the prioritisation of different consumptive water usages, imposition of restrictions and bans, raising of water tariffs and higher production costs to industry. The partitioning of precipitation into evaporation, storage and runoff depends on the local variability in meteorological variables and site-specific characteristics e.g., topography, soils and vegetation. The response of chalk catchments to meteorological forcing especially precipitation is of particular interest because of the preferential flow through the weathered formation. This makes the observed stream discharge groundwater-dominated and hence, out of phase with precipitation. One relevant question is how sensitive the low flow characteristics of such a chalk catchment is to changes in climate and land use. It is thus important to understand all the factors that control low stream discharge periods. In this study we present the results from numerical sensitivity analysis experiments performed with a detailed physically-based model on the Kennet, a sub-catchment of the River Thames, in the UK during the historical drought years of the 1970's.

  7. Ca2+ transient decline and myocardial relaxation are slowed during low flow ischemia in rat hearts.

    PubMed Central

    Camacho, S A; Brandes, R; Figueredo, V M; Weiner, M W

    1994-01-01

    The mechanisms that impair myocardial relaxation during ischemia are believed to involve abnormalities of calcium handling. However, there is little direct evidence to support this hypothesis. Therefore, we sought to determine whether the time constant of cytosolic calcium ([Ca2+]c) decline (tau Ca) was increased during low flow ischemia, and if there was a relationship between the time constant of left ventricular pressure decline (tau P) and tau Ca. Isolated perfused hearts were studied using indo-1 fluorescence ratio as an index of [Ca2+]c.tau P was used as an index of myocardial relaxation. The time constant of decline of the indo-1 ratio increased from 74 +/- 5 ms to 95 +/- 4, 144 +/- 10, and to 204 +/- 16 ms when coronary flow was reduced was reduced to 50, 20, and 10% of control, respectively. Indo-1 transients were calibrated to calculate tau Ca. tau Ca increased from 67 +/- 6 ms to 108 +/- 9 and 158 +/- 19 ms when coronary flow was reduced to 20 and 10% of control, respectively. There was a linear relationship between tau Ca and tau P (r = 0.82). These data support the hypothesis that during low flow ischemia, impaired myocardial relaxation may be caused by slowing of [Ca2+]c decline. PMID:8132781

  8. Assessment of processes affecting low-flow water quality of Cedar Creek, west-central Illinois

    USGS Publications Warehouse

    Schmidt, Arthur R.; Freeman, W.O.; McFarlane, R.D.

    1989-01-01

    Water quality and the processes that affect dissolved oxygen, nutrient (nitrogen and phosphorus species), and algal concentrations were evaluated for a 23.8-mile reach of Cedar Creek near Galesburg, west-central Illinois, during periods of warm-weather, low-flow conditions. Water quality samples were collected and stream conditions were measured over a diel (24 hour) period on three occasions during July and August 1985. Analysis of data from the diel-sampling periods indicates that concentrations of iron, copper, manganese, phenols, and total dissolved-solids exceeded Illinois ' general-use water quality standards in some locations. Dissolved-oxygen concentrations were less than the State minimum standard throughout much of the study reach. These data were used to calibrate and verify a one-dimensional, steady-state, water quality model. The computer model was used to assess the relative effects on low-flow water quality of processes such as algal photosynthesis and respiration, ammonia oxidation, biochemical oxygen demand, sediment oxygen demand, and stream reaeration. Results from model simulations and sensitivity analysis indicate that sediment oxygen demand is the principal cause of low dissolved-oxygen concentrations in the creek. (USGS)

  9. Method for estimating low-flow statistics for ungaged streams in the lower Hudson River Basin, New York

    USGS Publications Warehouse

    Barnes, C.R.

    1986-01-01

    Seven-day, 10-year and 7-day, 2-year low flow statistics were related to selected basin characteristics by multiple-regression analysis for 53 sites with watershed areas of less than 100 sq mi in the lower Hudson River basin. A common 20-year period of record was selected to ensure comparability of results. The most significant variable was the percentage of drainage basin underlain by stratified drift. The lowest standard errors of estimate were obtained from equations giving results in terms of discharge/sq mi during low-flow conditions. The statistically significant basin characteristics needed for estimating low flow were percentage of basin containing stratified drift, mean basin elevation, and mean annual precipitation. The smallest standard errors for 7-day, 10-year and 7-day, 2-year low flows obtained were 51% of the mean and 39% of the mean, respectively. (USGS)

  10. Low-flow routing in the Lehigh and Delaware Rivers, Pennsylvania

    USGS Publications Warehouse

    Flippo, H.N., Jr.

    1988-01-01

    Flow-routing studies were made to evaluate the response of the Lehigh and Delaware Rivers to low-flow augmentative releases from two reservoirs --Francis E. Walter Reservoir and Beltzville Lake--in the Lehigh River basin. Digital routing models that use diffusion-analogy methods to convolute flows with system-response functions were developed to simulate daily flows at selected sites. Model errors, for five sites and for periods of 1 year or more, were mostly between 3 and 12 percent in terms of absolute errors in daily flows and were mostly within 4 percent for flow volumes. The developed models were satisfactory for predicting hydrographic response at eight sites in the reach from White Haven, Pennsylvania to Trenton, New Jersey. However, abrupt changes in the flow rate of the Lehigh River at the Bethlehem and the Glendon gaging stations could not be adequately replicated with the model. The model tends to underestimate peaks by as much as 30 percent and to overestimate some low flows of short duration by as much as 20 percent. This occurs primarily because inflows from ungaged areas could not be reliably modeled throughout their ranges by use of flow records for gaged streams. The model will underestimate long-duration low flows at the Glendon site for periods when underflows at the gaging stations on Little Lehigh and Monocacy Creeks are significant. The models were used to route hypothetical releases from Francis E. Walter Reservoir during a low-flow period. The model for the Lehigh River indicated that an added release of 50 ft3/s (cubic feet per second) over a 64-day period during the severe drought in the summer of 1965 would have increased minimum flows for this period at Bethlehem and Glendon by approximately the same amount. A hypothetical release of 200 ft3/s for the period July 20-22, 1965, which is about eight times the actual release in this period, would have been attenuated by about 25 percent when it reached the Bethlehem gage. The synthesized

  11. Development of a low-flow multiplexed interface for capillary electrophoresis/electrospray ion trap mass spectrometry using sequential spray.

    PubMed

    Chen, Chao-Jung; Li, Fu-An; Her, Guor-Rong

    2008-05-01

    A multiplexed CE-MS interface using four low-flow sheath liquid ESI sprayers has been developed. Because of the limited space between the low-flow sprayers and the entrance aperture of the ESI source, multichannel analysis is difficult using conventional rotating plate approaches. Instead, a multiplexed low-flow system was achieved by applying an ESI potential sequentially to the four low-flow sprayers, resulting in only one sprayer being sprayed at any given time. The synchronization of the scan event and the voltage relays was accomplished by using the data acquisition signal from the IT mass spectrometer. This synchronization resulted in the ESI voltage being sequentially applied to each of the four sprayers according to the corresponding scan event. With this design, a four-fold increase in analytical throughput was achieved. Because of the use of low-flow interfaces, this multiplexed system has superior sensitivity than a rotating plate design using conventional sheath liquid interfaces. The multiplexed design presented has the potential to be applied to other low-flow multiplexed systems, such as multiplexed capillary LC and multiplexed CEC. PMID:18409161

  12. Effects of watershed land use and geomorphology on stream low flows during severe drought conditions in the southern Blue Ridge Mountains, Georgia and North Carolina

    EPA Science Inventory

    Watershed land use and topographic variability influence stream low flows, yet their interactions and relative influence remain unresolved. Our objective was to assess the relative influences of land use and watershed geomorphic characteristics on low flow variability in the sour...

  13. Noise-induced convergence of the low flow rate chaos in the Belousov-Zhabotinsky reaction

    NASA Astrophysics Data System (ADS)

    Yoshimoto, Minoru; Nakaiwa, Masaru; Akiya, Takaji; Ohmori, Takao; Yamaguchi, Tomohiko

    The effect of noise on the low flow-rate chaos in the Belousov-Zhabotinsky (BZ) reaction was studied. The chaos was simulated using the three-variable model of Györgyi and Field. Gaussian white noise was imposed on the flow-rate of the reactant solutions fed into CSTR to simulate the so-called type P noise. The range of average noise amplitudes was chosen between 0.01% and 1% related to the inverse residence time. The calculated time series were analyzed on the basis of their Fourier spectra, maximum Lyapunov exponent, Kolmogorov entropies, return maps and invariant density. We found that the noise induces partial order of the period-3-like oscillations in the low flowrate chaos.

  14. Pneumocephalus and subcutaneous scalp emphysema in a neonate on a low-flow nasal cannula.

    PubMed

    Sugimoto, Ai; Takahashi, Masashi; Shiraishi, Shuichi; Watanabe, Maya; Jiyong, Moon; Tsuchida, Masanori

    2016-05-01

    A 15-day-old boy after intracardiac repair was discharged from the intensive care unit with a low-flow nasal cannula for oxygen administration. The cannula was a 4-Fr multi-purpose tube with a side hole that was inserted into his left nostril. Next day, he suddenly developed pneumocephalus emerging from the right periorbital swelling and extending to his face and subcutaneous scalp over the next 6 h. A computed tomography (CT) scan revealed massive air pockets in the orbit, subdural space, subcutaneous scalp, and face. The nasal cannula was found to have been inserted deeper than we thought and was thus presumed to be the source of the air pockets. We immediately removed the cannula. Follow-up CTs revealed rapid resolution of the intracranial and subcutaneous air. The subcutaneous emphysema completely disappeared over the next 4 days, and he was discharged without any incident. PMID:25038900

  15. Assessment of low-flow water quality in Richland Creek, Illinois

    USGS Publications Warehouse

    Freeman, W.O.; Schmidt, A.R.

    1986-01-01

    To study the effects of urbanization on water quality, the relations of several stream processes to concentrations of dissolved oxygen and other constituents were evaluated during low-flow periods for a 30.1-mi reach of Richland Creek in southwestern Illinois. The study used both measured data and computer simulations. Reaeration rates and traveltimes were measured at various flow rates using a steady-state, gas-tracer technique. Sediment-oxygen demands were measured at several locations throughout the study reach. Stream discharge, stage, temperature, and chemical-constituent concentrations were measured during two 24-hr periods in July and August 1984. The data were then used to describe water quality and to calibrate and verify the QUAL-II one-dimensional, steady-state, water quality model. (USGS)

  16. Hydroclimatic controls on late-summer low flow in British Columbia, Canada

    NASA Astrophysics Data System (ADS)

    Stahl, K.; Moore, R. D.; Allen, D. M.; Whitfield, P. H.

    2009-05-01

    For catchments in the Pacific Northwest of North America the summer period is typically dominated by low flows associated with the relatively warm, dry summers in that region. In recent years streamflow during this period has been critical in terms of water use and fisheries, and there is increasing concern regarding how future climate change with potentially more severe summer droughts may affect late-summer flows. In addition, it is feared that earlier snowmelt timing in spring causes longer recession periods and consequently lower streamflow during summer. This study examined the sensitivity of late summer flows of 153 unregulated rivers over the period 1976-2003 to hydroclimatic influences by fitting regression models using simultaneous and lagged variables of precipitation and timing and magnitude of the snowmelt. To assess potential additional influences of long-term storage changes the residuals were tested for trends and serial correlation. A decrease in September flows across most of the region is broadly consistent with a decline in September precipitation. The most important control on August flows for all streamflow regimes is August precipitation. Lagged variables including July precipitation and the previous winter's precipitation are also positively but more weakly related to August streamflow. Rain-dominated and hybrid catchments tended to have positive trends in their residuals in August, suggesting an increasing trend in groundwater storage. Snow-melt dominated catchments showed no tendency to trends but the runs test detected a substantial number of stations with non-random residuals. This regional study greatly improves the understanding of the hydroclimatic influences on extreme summer low flow in the region. Results suggest that (the less predictable) summer climate is a larger influence than previously assumed. They also help to identify where seasonal snow processes or long- term groundwater storage should be considered in model development

  17. Low-flow profiles of the upper Savannah and Ogeechee Rivers and tributaries in Georgia

    USGS Publications Warehouse

    Carter, R.F.; Hopkins, E.H.; Perlman, H.A.

    1988-01-01

    Low flow information is provided for use in an evaluation of the capacity of streams to permit withdrawals or to accept waste loads without exceeding the limits of State water quality standards. The purpose of this report is to present the results of a compilation of available low flow data in the form of tables and ' 7Q10 flow profiles ' (minimum average flow for 7 consecutive days with a 10-yr recurrence interval)(7Q10 flow plotted against distance along a stream channel) for all streams reaches of the Upper Savannah and Ogeechee Rivers and tributaries where sufficient data of acceptable accuracy are available. Drainage area profiles are included for all stream basins larger than 5 sq mi, except for those in a few remote areas. This report is the third in a series of reports that will cover all stream basins north of the Fall Line in Georgia. It includes the Georgia part of the Savannah River basin from its headwaters down to and including McBean Creek, and Brier Creek from its headwaters down to and including Boggy Gut Creek. It also includes the Ogeechee River from its headwaters down to and including Big Creek, and Rocky Comfort Creek (tributary to Ogeechee River) down to the Glascock-Jefferson County line. Flow records were not adjusted for diversions or other factors that cause measured flows to represent other than natural flow conditions. The 7-day minimum flow profile was omitted for stream reaches where natural flow was known to be altered significantly. (Lantz-PTT)

  18. Low-flow Characteristics of Eau Claire River Basin near Antigo, Wisconsin

    USGS Publications Warehouse

    Holmstrom, B.K.

    1975-01-01

    This report presents low-flow characteristics at six sites on streams in the Eau Claire River basin near Antigo, Wis., where applications for irrigation permits were made. The low-flow characteristics presented are the annual minimum 7-day mean flows at the 2-year recurrence interval and 10-year recurrence interval. A seepage run made October 10, 1974, showed a substantial gain in discharge from site 2 (3.75 ft3/s [cubic feet per second] or 0.11 m3/s (cubic metres per second) to site 6 (30.6 ft3/s or 0.87 m3/s) on the East Branch Eau Claire River and from site 12 (3.98 ft3/s or 0.11 m3/s) to site 16 (18.1 ft3/s or 0.51 m3/s) on the West Branch Eau Claire River; a fairly constant discharge between sites 6 (30.6 ft3/s or 0.87 m3/s) and 11 (32.3 ft3/s or 0.91 m3/s) on the East Branch and sites 16 (18.1 ft3/s or 0.51 m3/s) and 20 (18.8 ft3/s or 0.53 m3/s) on the West Branch; and a substantial gain in discharge from site 23 (57.3 ft3/s or 1.62 m3/s) to site 24 (63.4 ft3/s or 1.80 m3/s) on the Eau Claire River. A gaging station was established at the downstream potential irrigation site to collect continuous stage and discharge data on streamflow to assist the Wisconsin Department of Natural Resources in the regulation of irrigation withdrawals.

  19. Simulations of a Liquid Hydrogen Inducer at Low-Flow Off-Design Flow Conditions

    NASA Technical Reports Server (NTRS)

    Hosangadi, A.; Ahuja, V.; Ungewitter, R. J.

    2005-01-01

    The ability to accurately model details of inlet back flow for inducers operating a t low-flow, off-design conditions is evaluated. A sub-scale version of a three-bladed liquid hydrogen inducer tested in water with detailed velocity and pressure measurements is used as a numerical test bed. Under low-flow, off-design conditions the length of the separation zone as well as the swirl velocity magnitude was under predicted with a standard k-E model. When the turbulent viscosity coefficient was reduced good comparison was obtained a t all the flow conditions examined with both the magnitude and shape of the profile matching well with the experimental data taken half a diameter upstream of the leading edge. The velocity profiles and incidence angles a t the leading edge itself were less sensitive to the back flow length predictions indicating that single-phase performance predictions may be well predicted even if the details of flow separation modeled are incorrect. However, for cavitating flow situations the prediction of the correct swirl in the back flow and the pressure depression in the core becomes critical since it leads to vapor formation. The simulations have been performed using the CRUNCH CFD(Registered Trademark) code that has a generalized multi-element unstructured framework and a n advanced multi-phase formulation for cryogenic fluids. The framework has been validated rigorously for predictions of temperature and pressure depression in cryogenic fluid cavities and has also been shown to predict the cavitation breakdown point for inducers a t design conditions.

  20. River-aquifer interactions, geologic heterogeneity, and low-flow management

    USGS Publications Warehouse

    Fleckenstein, J.H.; Niswonger, R.G.; Fogg, G.E.

    2006-01-01

    Low river flows are commonly controlled by river-aquifer exchange, the magnitude of which is governed by hydraulic properties of both aquifer and aquitard materials beneath the river. Low flows are often important ecologically. Numerical simulations were used to assess how textural heterogeneity of an alluvial system influences river seepage and low flows. The Cosumnes River in California was used as a test case. Declining fall flows in the Cosumnes River have threatened Chinook salmon runs. A ground water-surface water model for the lower river basin was developed, which incorporates detailed geostatistical simulations of aquifer heterogeneity. Six different realizations of heterogeneity and a homogenous model were run for a 3-year period. Net annual seepage from the river was found to be similar among the models. However, spatial distribution of seepage along the channel, water table configuration and the level of local connection, and disconnection between the river and aquifer showed strong variations among the different heterogeneous models. Most importantly, the heterogeneous models suggest that river seepage losses can be reduced by local reconnections, even when the regional water table remains well below the riverbed. The percentage of river channel responsible for 50% of total river seepage ranged from 10% to 26% in the heterogeneous models as opposed to 23% in the homogeneous model. Differences in seepage between the models resulted in up to 13 d difference in the number of days the river was open for salmon migration during the critical fall months in one given year. Copyright ?? 2006 The Author(s).

  1. Influence of water use of the Kamni\\vska Bistrica river on low flows

    NASA Astrophysics Data System (ADS)

    Kobold, M.; Brilly, M.; Koren, S.

    2009-04-01

    The use of water of the Kamni\\vska Bistrica river has very long tradition known from the Austro-Hungarian era when water was mostly used for operating of water mills. For that purposes the artificial channels were built on the both side of the river at the length of around 10 km on its lower stream. The Kamni\\vska Bistrica rises in the Kamnik Alps and with its length of 33 km is known as torrential river. Nowadays the main use of water is designed for operating of small hydroelectric plants located on the channels, as technological water and fish farming. On Sunday morning 28 September 2008 the main stream of the Kamni\\vska Bistrica river downstream of the origin of channels dried up and more than 500 kg of fishes died in that part of the stream. During the September and October 2008 the precipitation was below the average on the catchment and this was reflected in low flows of the streams. In that hydrological condition some removals of sands were performed from the river bad. To find out the reason for drying up of the main stream, the hydrological analysis was done for the period from September to October 2008 using the data of national hydrological monitoring network. In spite of the low flows the results show that the discharges on the nearest water measurement stations without anthropogenic influences were above the mean low periodical discharges. Almost all water from the main stream was diverted to channels using for the production of electricity not taking into account that some amount of water is needed in the main, sensitive part of the river. This event was not the first, but that time some actions occurred by the competent authority with setting up the rules of diversion of water from the Kamni\\vska Bistrica river and determination of ecologically acceptable flow.

  2. Low flow and high flow responses to converting natural grassland into bluegum ( Eucalyptus globulus) in Nilgiris watersheds of South India

    NASA Astrophysics Data System (ADS)

    Sikka, A. K.; Samra, J. S.; Sharda, V. N.; Samraj, P.; Lakshmanan, V.

    2003-01-01

    A concern has been raised in many parts of the world over the effect of large scale planting of Eucalyptus on hydrological behaviour of small watersheds. Hydrological response of watersheds due to conversion of natural grasslands into bluegum ( Eucalyptus globulus) plantations on low flows and high flows has been presented in this paper. The concept of using low flow index (LFI) as a tool to study and quantify the effects of bluegum plantation on low flow regime has been demonstrated. Conversion of natural grasslands into bluegum plantations has resulted in decreased low flow volume as well as peak flow, which in turn increased the soil moisture losses. These effects were more pronounced during the second rotation (i.e. first coppiced growth) as compared to the first rotation. Significant reduction in low flow as a result of decline in base flow could be predicted with LFI decreasing by 2.0 and 3.75 times, in the first and second rotation, respectively. Moderation in peak discharge rates was also observed as a result of bluegum plantation. Probability plots of peak discharge tend to suggest that the effect of bluegum plantation on peak flows become insignificant for the floods with higher return periods. These results clearly suggest that caution need to be exercised while planning large scale conversion of natural grasslands into bluegum plantations in the catchments of hydro-electric reservoirs in the Nilgiris which adversely affects water availability especially during lean flow period.

  3. Low-flow characteristics and profiles for the Rocky River in the Yadkin-Pee Dee River basin, North Carolina, through 2002

    USGS Publications Warehouse

    Weaver, J. Curtis; Fine, Jason M.

    2003-01-01

    An understanding of the magnitude and frequency of low-flow discharges is an important part of protecting surface-water resources and planning for municipal and industrial economic expansion. Low-flow characteristics are summarized for 12 continuous-record gaging stations and 44 partial-record measuring sites in the Rocky River basin in North Carolina. Records of discharge collected through the 2002 water year at continuous-record gaging stations and through the 2001 water year at partial-record measuring sites were used. Flow characteristics included in the summary are (1) average annual unit flow; (2) 7Q10 low-flow discharge, the minimum average discharge for a 7-consecutive-day period occurring, on average, once in 10 years; (3) 30Q2 low-flow discharge; (4) W7Q10 low-flow discharge, which is similar to 7Q10 discharge but is based only on flow during the winter months of November through March; and (5) 7Q2 low-flow discharge. The Rocky River basin drains 1,413 square miles (mi2) of the southern Piedmont Province in North Carolina. The Rocky River is about 91 miles long and merges with the Yadkin River in eastern Stanly County to form the Pee Dee River, which discharges into the Atlantic Ocean in South Carolina. Low-flow characteristics compiled for selected sites in the Rocky River basin indicated that the potential for sustained base flows in the upper half of the basin is relatively higher than for streams in the lower half of the basin. The upper half of the basin is underlain by the Charlotte Belt, where streams have been identified as having moderate potentials for sustained base flows. In the lower half of the basin, many streams were noted as having little to no potential for sustained base flows. Much of the decrease in base-flow potential is attributed to the underlying rock types of the Carolina Slate Belt. Of the 19 sites in the basin having minimal (defined as less than 0.05 cubic foot per second) or zero 7Q10 discharges, 18 sites are located in the

  4. Generalized function of the parameters in the storage-discharge relation for low flows

    NASA Astrophysics Data System (ADS)

    Fujimura, Kazumasa; Iseri, Yoshihiko; Kanae, Shinjiro; Murakami, Masahiro

    2015-04-01

    The accurate estimation of low flows can contribute to better water resource management and more reliable evaluation of the impact of climate change on water resources. For the case of low flows, the nonlinearity of the discharge Q associated with the storage S was originally proposed by Horton (1936) as the power function Q=KSN, where K is a constant and N is the exponent. Although the Q(S) relations for groundwater runoff from unconfined aquifers have been treated as second-order polynomial functions on the basis of the hydraulic investigation by Ding (1966), the general power function Q = KNSN was introduced into the unit hydrograph model for overland flow and the parameters K and N were calibrated by Ding (2011). According to recent studies, the value of the exponent N is varied between 1 and 3 or higher by calibration (e.g., Wittenberg, 1994 and Ding, 2011); however, it is currently unclear whether the optimum value of N has the rule. Fujimura et al. (2014) applied the general power function Q = KNSN for low flows in mountainous basins over a period spanning more than 10 years using hourly data, and carried out sensitivity analysis using a hydrological model for 19 900 sets of the two parameters K and N, in which the exponent N was varied between 1 and 100 in steps of 0.5. The results showed that the optimum relation between N and K could be characterized by the exponential function K=1/(α Nβ), where α and β are constants. Moreover, the lowest error in the sensitivity analysis was obtained by using an exponent N of 100. The aim of this study is to extend the previous study of Fujimura et al. to clarify the properties of the K(N) relations. A sensitivity analysis is performed efficiently using a hydrological model, in which the exponent N is varied between 1 and 100 000 along the neighborhood of the exponential function K=1/(α Nβ). The hourly hydrological model used in this study comprises the Diskin-Nazimov infiltration model, groundwater recharge and

  5. Decision support system based on DPSIR framework for a low flow Mediterranean river basin

    NASA Astrophysics Data System (ADS)

    Bangash, Rubab Fatima; Kumar, Vikas; Schuhmacher, Marta

    2013-04-01

    The application of decision making practices are effectively enhanced by adopting a procedural approach setting out a general methodological framework within which specific methods, models and tools can be integrated. Integrated Catchment Management is a process that recognizes the river catchment as a basic organizing unit for understanding and managing ecosystem process. Decision support system becomes more complex by considering unavoidable human activities within a catchment that are motivated by multiple and often competing criteria and/or constraints. DPSIR is a causal framework for describing the interactions between society and the environment. This framework has been adopted by the European Environment Agency and the components of this model are: Driving forces, Pressures, States, Impacts and Responses. The proposed decision support system is a two step framework based on DPSIR. Considering first three component of DPSIR, Driving forces, Pressures and States, hydrological and ecosystem services models are developed. The last two components, Impact and Responses, helped to develop Bayesian Network to integrate the models. This decision support system also takes account of social, economic and environmental aspects. A small river of Catalonia (Northeastern Spain), Francoli River with a low flow (~2 m3/s) is selected for integration of catchment assessment models and to improve knowledge transfer from research to the stakeholders with a view to improve decision making process. DHI's MIKE BASIN software is used to evaluate the low-flow Francolí River with respect to the water bodies' characteristics and also to assess the impact of human activities aiming to achieve good water status for all waters to comply with the WFD's River Basin Management Plan. Based on ArcGIS, MIKE BASIN is a versatile decision support tool that provides a simple and powerful framework for managers and stakeholders to address multisectoral allocation and environmental issues in river

  6. Climate driven variability and detectability of temporal trends in low flow indicators for Ireland

    NASA Astrophysics Data System (ADS)

    Hall, Julia; Murphy, Conor; Harrigan, Shaun

    2013-04-01

    Observational data from hydrological monitoring programs plays an important role in informing decision makers of changes in key hydrological variables. To analyse how changes in climate influence stream flow, undisturbed river basins with near-natural conditions limited from human influences are needed. This study analyses low flow indicators derived from observations from the Irish Reference Network. Within the trend analysis approach the influence of individual years or sub-periods on the detected trend are analysed using sequential trend tests on all possible periods (of at least 10 years in length) by varying the start and end dates of records for various indicators. Results from this study highlight that the current standard approach using fixed periods to determine long term trends is not appropriate as statistical significance and direction of trends from short term records do not persist continuously over entire record and can be heavily influenced by extremes within the record. The importance of longer records in contextualising short term trends derived from fixed-periods influenced by natural annual, inter-annual and multi-decadal variability is highlighted. Due to the low signal (trend) to noise (variability) ratio, the apparent trends derived from the low flow indicators cannot be used as confident guides to inform future water resources planning and decision making on climate change. Infact, some derived trends contradict expected climate change impacts and even small changes in study design can change the outcomes to a high degree. Therefore it is important not only to evaluate the magnitude of trends derived from monitoring data but also when a trend of a certain magnitude in a given indicator will be detectable to inform decision making or what changes might be required to detect trends for a certain significance level. In this study, the influence of observed variance in the monitoring records on the expected detection times for trends with a

  7. Critical heat-flux experiments under low-flow conditions in a vertical annulus. [PWR; BWR; LMFBR

    SciTech Connect

    Mishima, K.; Ishii, M.

    1982-03-01

    An experimental study was performed on critical heat flux (CHF) at low flow conditions for low pressure steam-water upward flow in an annulus. The test section was transparent, therefore, visual observations of dryout as well as various instrumentations were made. The data indicated that a premature CHF occurred due to flow regime transition from churn-turbulent to annular flow. It is shown that the critical heat flux observed in the experiment is essentially similar to a flooding-limited burnout and the critical heat flux can be well reproduced by a nondimensional correlation derived from the previously obtained criterion for flow regime transition. The observed CHF values are much smaller than the standard high quality CHF criteria at low flow, corresponding to the annular flow film dryout. This result is very significant, because the coolability of a heater surface at low flow rates can be drastically reduced by the occurrence of this mode of CHF.

  8. Applications of low-flow LC-SRM for the analysis of large molecules in pharmaceutical R&D.

    PubMed

    Lassman, Michael E; Fernandez-Metzler, Carmen

    2014-01-01

    Although ligand-binding assays are frequently employed to measure large molecules, the use of LC-SRM assays is increasingly popular due to the inherent selectivity advantage and the ability to operate without exquisitely selective antibodies. Until recently LC-SRM assays have been unable to compete with ligand-binding assays in terms of sensitivity. However, the use of low-flow chromatography prior to mass spectrometry has played a crucial role in increasing the sensitivity of LC-SRM platforms and enabling measurements of large molecules that had previously been unmeasurable. In this article, we highlight some technical advances, describe strategies for employing low-flow chromatography, and review recent literature that describes implementation of low-flow LC-SRM to support large-molecule analysis in pharmaceutical R&D. PMID:25157490

  9. Relating low-flow characteristics to the base flow recession time constant at partial record stream gauges

    USGS Publications Warehouse

    Eng, K.; Milly, P.C.D.

    2007-01-01

    Base flow recession information is helpful for regional estimation of low-flow characteristics. However, analyses that exploit such information generally require a continuous record of streamflow at the estimation site to characterize base flow recession. Here we propose a simple method for characterizing base flow recession at low-flow partial record stream gauges (i.e., sites with very few streamflow measurements under low-streamflow conditions), and we use that characterization as the basis for a practical new approach to low-flow regression. In a case study the introduction of a base flow recession time constant, estimated from a single pair of strategically timed streamflow measurements, approximately halves the root-mean-square estimation error relative to that of a conventional drainage area regression. Additional streamflow measurements can be used to reduce the error further.

  10. Predicting Low Flow Conditions from Climatic Indices - Indicator-Based Modeling for Climate Change Impact Assessment

    NASA Astrophysics Data System (ADS)

    Fangmann, Anne; Haberlandt, Uwe

    2014-05-01

    In the face of climate change, the assessment of future hydrological regimes has become indispensable in the field of water resources management. Investigation of potential change is vital for proper planning, especially with regard to hydrological extremes. Commonly, projection of future streamflow is done applying process-based hydrological models, using climate model data as input, whose complex model structures generally require excessive amounts of time and effort for set-up and computation. This study aims at identifying practical alternatives to the employment of sophisticated models by considering simpler, yet sufficiently accurate methods for modeling rainfall-runoff relations with regard to hydrological extremes. The focus is thereby put on the prediction of low flow periods, which are, in contrast to flood events, characterized by extended durations and spatial dimensions. The models to be established in this study base on indicators, which characterize both meteorological and hydrological conditions within dry periods. This approach makes direct use of the coupling between atmospheric driving forces and streamflow response with the underlying presumption that low-precipitation and high-evaporation periods result in diminished flow, implying that relationships exist between the properties of both meteorological and hydrological events (duration, volume, severity etc.). Eventually, optimal combinations of meteorological indicators are sought that are suitable to predict various low flow characteristics with satisfactory accuracy. Two approaches for model specification are tested: a) multiple linear regression, and b) Fuzzy logic. The data used for this study are daily time series of mean discharge obtained from 294 gauges with variable record length situated in the federal state of Lower Saxony, Germany, as well as interpolated climate variables available for a period from 1951 to 2011. After extraction of a variety of indicators from the available

  11. Low flow forecasting with data driven models that include and models that do not include hydrological knowledge - a comparison study

    NASA Astrophysics Data System (ADS)

    Stravs, L.; Brilly, M.

    2009-04-01

    Good and accurate long-term low flow forecasting is important in the fields of sustainable water management, water rights, water supply management, industrial use of freshwater, optimization of the reservoir operations for the production of electric energy and other water-related disciplines. Today, low flow forecasting is usually performed as an integrated part of calibrated rainfall-runoff models, but in our research we developed two types of simple empirical 7-day ahead low flow forecasting models by using the M5 machine learning method for the generation of regression and model trees. Development of the first type of models was based solely on the application of the M5 machine learning method (1-, 2-, 3-, 4-, 5-, 6-and 7-day lead time low flow forecasting model trees were developed from using only past flow data and then combined to produce 7-day ahead forecast curve), while the development of the other type of models included the conceptual knowledge of linear reservoir recession functions AND application of the M5 machine learning method (we modelled the streamflow recession coefficient k as a function of the flow rate at which the 7-day low flow forecast is made and the decrease in the flow rate from the previous day). Both types of 7-day ahead low flow forecasting models were developed by using the same type and amount of data and were built for the Podhom gauging station on the Radovna River and the Medvode gauging station on the Sora River (both are Slovenian tributaries of the Sava River, which itself is a Danube River tributary). The results were compared and tested both visually and numerically.

  12. Centurial changes in the augmentation of low flows by snow and glacier melt in the River Rhine

    NASA Astrophysics Data System (ADS)

    Stahl, Kerstin; Kohn, Irene; Boehm, Mario; Freudiger, Daphné; Gerlinger, Kai; Seibert, Jan; Weiler, Markus

    2016-04-01

    Low flows can have severe consequences for river ecosystems, energy production, navigation and other river water uses. In the mid- and downstream reaches of the River Rhine late-summer low flows are augmented by the ice melt component from the glaciated mountain headwaters upstream. As the glaciers are retreating fast, the quantification of this augmentation has become a highly relevant question. Based on results from a long-term modelling experiment, this study explores the contributions of snow and ice melt to the River Rhine's daily streamflows in extreme low flow events since 1900 from a downstream perspective. While the glacier ice melt component only contributes a few percent to the average annual flow of the Rhine downstream of Switzerland, its contribution is much higher during drought events such as those that have caused extreme low flows in the late summers of 1921, 1947, and 2003. In these situations, over 30% of the low flow downstream of Basel was comprised of ice melt and this fraction remains rather similar further along the Rhine to the Netherlands. Despite the loss of glacier volume and area in the headwaters over the course of the 20th century, an increasingly negative mass balance appears to have compensated for the glacier retreat, resulting in little long-term change to the ice melt component in summer streamflow. However, for an extreme event such as that in 2003, the ice melt component would have contributed a third more flow if it had occurred in the early 1900s. We use the modeled long-term coupled changes in glaciers and hydrology to quantify the low flow hazard that may loom ahead as the glaciers continue to decline.

  13. Effect of different uncertainty sources on the skill of 10 day ensemble low flow forecasts for two hydrological models

    NASA Astrophysics Data System (ADS)

    Demirel, Mehmet C.; Booij, Martijn J.; Hoekstra, Arjen Y.

    2013-07-01

    This paper aims to investigate the effect of uncertainty originating from model inputs, parameters and initial conditions on 10 day ensemble low flow forecasts. Two hydrological models, GR4J and HBV, are applied to the Moselle River and performance in the calibration, validation and forecast periods, and the effect of different uncertainty sources on the quality of low flow forecasts are compared. The forecasts are generated by using meteorological ensemble forecasts as input to GR4J and HBV. The ensembles provided the uncertainty range for the model inputs. The Generalized Likelihood Uncertainty Estimation (GLUE) approach is used to estimate parameter uncertainty. The quality of the probabilistic low flow forecasts has been assessed by the relative confidence interval, reliability and hit/false alarm rates. The daily observed low flows are mostly captured by the 90% confidence interval for both models. However, GR4J usually overestimates low flows whereas HBV is prone to underestimate them, particularly when the parameter uncertainty is included in the forecasts. The total uncertainty in GR4J outputs is higher than in HBV. The forecasts issued by HBV incorporating input uncertainty resulted in the most reliable forecast distribution. The parameter uncertainty was the main reason reducing the number of hits. The number of false alarms in GR4J is twice the number of false alarms in HBV when considering all uncertainty sources. The results of this study showed that the parameter uncertainty has the largest effect whereas the input uncertainty had the smallest effect on the medium range low flow forecasts.

  14. No-flow alarm disabled in respironics EverFlo oxygen concentrators equipped with optional low-flow flowmeter.

    PubMed

    2011-04-01

    Respironics EverFlo oxygen concentrators can be equipped with an optional internal low-flow flowmeter, but when this flowmeter is in place, the unit will not alarm for no-flow conditions. Facilities should consider using an oxygen concentrator other than the EverFlo for pediatric patients, who may be harmed by a loss of supplemental oxygen. Facilities that choose to continue using the EverFlo with the low-flow flowmeter should ensure that pediatric patients are appropriately monitored, such as with a pulse oximeter. PMID:23444572

  15. Comparative study of regionalization methods for simulating low-flows from a small number of model parameters

    NASA Astrophysics Data System (ADS)

    Garcia, Florine; Folton, Nathalie; Oudin, Ludovic; Arnaud, Patrick

    2015-04-01

    Issues with water resource management result from both an increasing demand and climate changes. The situations of low-flows, droughts and more generally lack of water are critically scrutinized. In this context, there is a need for tools to assist water agencies in the prediction and management of reference low-flows at gauged and ungauged catchment locations. IRSTEA developed GR2M-LoiEau, a conceptual distributed rainfall-runoff model, which is combined with a regionalized model of snow storage and melt. GR2M-LoiEau relies on two parameters which are regionalized and mapped throughout France. This model allows to cartography annual and monthly reference low-flows. The input meteorological data come from the distributed mesoscale atmospheric analysis system SAFRAN, which provides daily solid and liquid precipitations and temperatures data from everywhere in the French territory. In order to fully exploit these daily meteorological data to estimate daily statistics on low flows, a new version of GR2M-LoiEau is being developed at a daily time step, yet keeping only a few regionalized parameters. The aim of this study is to design a comprehensive set of tests to allow comparing low-flows obtained with different regionalization methods used to estimate low-flow model parameters. The new version of GR2M-LoiEau being not yet operational, the tests are made with GR4J (Perrin, 2002), a conceptual rainfall-runoff model, which already provides daily estimations, but involves four parameters that cannot easily be regionalized. Many studies showed the good prediction performances of this model. This work includes two parts. On the one hand, good criteria must be identified to evaluate and compare model results, good predictions of the model being expected about low flows and reference low flows, but also annual means and high flows. On the other hand, two methods of regionalization will have to be compared to estimate model parameters. The first one is rough, all the

  16. Low flow measurement for infusion pumps: implementation and uncertainty determination of the normalized method

    NASA Astrophysics Data System (ADS)

    Cebeiro, J.; Musacchio, A.; Fernández Sardá, E.

    2011-12-01

    Intravenous drug delivery is a standard practice in hospitalized patients. As the blood concentration reached depends directly on infusion rate, it is important to use safe devices that guarantee output accuracy. In pediatric intensive care units, low infusion rates (i.e. lower than 10.0 ml/h) are frequently used. Thus, it would be necessary to use control programs to search for deviations at this flow range. We describe the implementation of a gravimetric method to test infusion pumps in low flow delivery. The procedure recommended by the ISO/IEC 60601-2-24 standard was used being a reasonable option among the methods frequently used in hospitals, such as infusion pumps analyzers and volumetric cylinders. The main uncertainty sources affecting this method are revised and a numeric and graphic uncertainty analysis is presented in order to show its dependence on flow. Additionally, the obtained uncertainties are compared to those presented by an automatic flow analyzer. Finally, the results of a series of tests performed on a syringe infusion pump operating at low rates are shown.

  17. [Is it necessary to humidify inhaled low-flow oxygen or low-concentration oxygen?].

    PubMed

    Miyamoto, Kenji

    2004-02-01

    In Japan, oxygen is routinely humidified in almost every hospital and clinic. In contrast, in Europe and North America, oxygen is not humidified as long as the oxygen flow is less than 4-5 L/min, according to the guidelines for oxygen therapy announced by the ACCP-NHLBI in 1984 and by AARC in 1992. In this paper, we demonstrate mathematically that: 1) the oxygen received through a nasal cannula at 0.5-4 L/min or through a Venturi mask at 24-40% constitutes only a small percentage of the patient's inspiratory tidal volume (2.4-19% and 3.8-24%, respectively), 2) the humidity deficit caused by inhaling unhumidified oxygen through a nasal cannula at 0.5-4 L/min or through a Venturi mask at 24% to 31% is very small compared with the water content delivered from the airway, and 3) this humidity deficit is easily compensated for by increasing the relative humidity of the room air a little, e.g., by only 4% in case of inhalation of 2 L/min of oxygen through a nasal cannula. Similar results are obtained when a Venturi mask is used to inhale oxygen. From these calculations, we conclude that routine humidification of low-flow oxygen or low-concentration oxygen is not justifiable in patients who need oxygen inhalation, as the humidity of room air is sufficient. PMID:15007913

  18. Information system "BW_Abfluss": regionalisation of flood, mean and low flow parameters

    NASA Astrophysics Data System (ADS)

    Blatter, A. S.; Liebert, J.; Preuss, P. A.; Szabadics, J.; Ihringer, J.

    2007-06-01

    On behalf of and in close collaboration with the institution of environment, measurements and conservation of the federal state of Baden-Württemberg (Landesanstalt für Umwelt, Messungen und Naturschutz Baden-Württemberg/LUBW/ see http://www.lubw.baden-wuerttemberg.de/) an innovative regionnalisation concept has been developed. This concept allows the supply of flood, mean or low flow parameters for 10 790 sites in Baden-Württemberg and an evaluation of the predicted impact of climate change on the flood situation. The extensive data basis for this regionalisation concept with numerous input parameters and varied result reporting made it necessary to select an appropriate database structure. New software was developed to help with the calculations, notably for: - upgrading the official areal water system register (Gewässerkundliches Flächenverzeichnis/GKFV) - proofing tools to maintain consistency - automatic parameter derivation with the software ESRI© ArcInfo. The results were published in electronic form and included a stand-alone geo-information software for easy and fast retrieval of data and results. The objective of this article is to describe the implementation of these new concepts for coupling Geographic Information System (GIS) and database needs to reach the identified requirements.

  19. Development of myoelectric control type speaking valve with low flow resistance

    NASA Astrophysics Data System (ADS)

    Ooe, Katsutoshi; Sakurai, Kohei; Mimaki, Shinya

    2015-12-01

    We aimed to develop welfare devices for patients with phonation disorder. One of these devices is the electrical controltype speaking valve system. The conventional speaking valves have one-way valve architecture, they open when the user breathes in, and they close when user breathes out and produce voices. This type is very simple and tough, but some users feel closeness in case of exhalation without phonation. This problem is caused by its mechanism what can not be controlled by user's will. Therefore, we proposed an electrical control-type speaking valve system to resolve this problem. This valve is controlled by neck myoelectric signal of sternohyoid muscle. From our previous report, it was clarified that this valve had better performance about easy-to-breath. Furthermore, we proposed the compact myoelectric control-type speaking valve system. The new-type speaking valve was enough small to attach the human body, and its opening area is larger than that of conventional one. Additionally, we described the improvement of flow channel shape by using of FEM analysis. According to the result of the analysis, it was clarified that the shape-improved speaking valve gets the low flow resistance channel in case of inspiration. In this report, we tried to make the flow resistance lower by the shape of current plates, in case of both inspiration and exhalation. From the result of FEM analysis, our speaking valve could get better flow channel than older one.

  20. Applying a low-flow CO2 removal device in severe acute hypercapnic respiratory failure.

    PubMed

    Sharma, Ajay S; Weerwind, Patrick W; Strauch, Uli; van Belle, Arne; Maessen, Jos G; Wouters, Emiel F M

    2016-03-01

    A novel and portable extracorporeal CO2-removal device was evaluated to provide additional gas transfer, auxiliary to standard therapy in severe acute hypercapnic respiratory failure. A dual-lumen catheter was inserted percutaneously in five subjects (mean age 55 ± 0.4 years) and, subsequently, connected to the CO2-removal device. The median duration on support was 45 hours (interquartile range 26-156), with a blood flow rate of approximately 500 mL/min. The mean PaCO2 decreased from 95.8 ± 21.9 mmHg to 63.9 ± 19.6 mmHg with the pH improving from 7.11 ± 0.1 to 7.26 ± 0.1 in the initial 4 hours of support. Three subjects were directly weaned from the CO2-removal device and mechanical ventilation, one subject was converted to ECMO and one subject died following withdrawal of support. No systemic bleeding or device complications were observed. Low-flow CO2 removal adjuvant to standard therapy was effective in steadily removing CO2, limiting the progression of acidosis in subjects with severe acute hypercapnic respiratory failure. PMID:26040584

  1. Assessment of low-flow water quality in the Du Page River, Illinois

    USGS Publications Warehouse

    Freeman, W.O.; Schmidt, A.R.; Stamer, J.K.

    1986-01-01

    The relations of several stream processes to concentrations of dissolved oxygen and other constituents during low-flow periods were evaluated for a 70.3-mile reach of the Du Page River in northeastern Illinois, using measured data and computer simulations. Reaeration rates and traveltimes were measured at various flow rates using a steady-state gas-tracer technique. Stream discharge, stage, temperature, and chemical constituent concentrations were measured during two 24-hour periods in July and August 1983. These data were used to describe water quality and to calibrate and verify the QUAL-II one dimensional, steady-state, water quality model. Dissolved oxygen concentrations did not meet the State water quality standards in several subreaches of the Du Page River. Concentrations were consistently below the State minimum dissolved oxygen standard in the downstream 8 miles of the East Branch Du Page River. Model simulations indicate that although ammonia oxidation played a role in the dissolved oxygen depletion, the primary factor was sediment oxygen demand. Other measured chemical constituents that did not comply with the State water quality standards in several subreaches of the river included ammonia, iron, fluoride, and total dissolved solids. (USGS)

  2. Databased comparison of Sparse Bayesian Learning and Multiple Linear Regression for statistical downscaling of low flow indices

    NASA Astrophysics Data System (ADS)

    Joshi, Deepti; St-Hilaire, André; Daigle, Anik; Ouarda, Taha B. M. J.

    2013-04-01

    SummaryThis study attempts to compare the performance of two statistical downscaling frameworks in downscaling hydrological indices (descriptive statistics) characterizing the low flow regimes of three rivers in Eastern Canada - Moisie, Romaine and Ouelle. The statistical models selected are Relevance Vector Machine (RVM), an implementation of Sparse Bayesian Learning, and the Automated Statistical Downscaling tool (ASD), an implementation of Multiple Linear Regression. Inputs to both frameworks involve climate variables significantly (α = 0.05) correlated with the indices. These variables were processed using Canonical Correlation Analysis and the resulting canonical variates scores were used as input to RVM to estimate the selected low flow indices. In ASD, the significantly correlated climate variables were subjected to backward stepwise predictor selection and the selected predictors were subsequently used to estimate the selected low flow indices using Multiple Linear Regression. With respect to the correlation between climate variables and the selected low flow indices, it was observed that all indices are influenced, primarily, by wind components (Vertical, Zonal and Meridonal) and humidity variables (Specific and Relative Humidity). The downscaling performance of the framework involving RVM was found to be better than ASD in terms of Relative Root Mean Square Error, Relative Mean Absolute Bias and Coefficient of Determination. In all cases, the former resulted in less variability of the performance indices between calibration and validation sets, implying better generalization ability than for the latter.

  3. TRENDS IN FLOODS AND LOW FLOWS IN THE UNITED STATES: IMPACT OF SPATIAL CORRELATION. (R824992,R826888)

    EPA Science Inventory

    Trends in flood and low flows in the US were evaluated using a regional average Kendall's S trend test at two spatial scales and over two timeframes. Field significance was assessed using a bootstrap methodology to account for the observed regional cross-correlation of streamflow...

  4. Low flows and temperatures of streams in the Seattle-Tacoma urban complex and adjacent areas, Washington

    USGS Publications Warehouse

    Hidaka, F.T.

    1972-01-01

    Data on the minimum flows of streams and water temperature are necessary for the proper planning and development of the water resources of urban Seattle-Tacoma and adjacent areas. The data on low flows are needed for such purposes as (1) designing and operating municipal and industrial water-supply systems; (2) classifying streams as to their potential for waste disposal; (3) defining the amount of water available for irrigation, for maintaining streamflow as required by law or agreement, and for fish propagation; and (4) designing water-storage facilities. Data on stream temperatures are important to many water users because of the many biological, chemical, and physical properties of water that are dependent on temperature. Agricultural and domestic users as well as municipal, industrial and fishery agencies are concerned with water temperatures. In this report, low-flow data are accompanied by information on seasonal variations in water temperatures at sites selected as representing regional stream-temperature patterns. Because low flows and high water temperatures commonly occur together, they may impose constraints on various uses of the region's streams. The following discussion deals first with low-flow trends in the region, then with stream temperatures, and finally with some of the resulting constraints.

  5. The skill of seasonal ensemble low-flow forecasts in the Moselle River for three different hydrological models

    NASA Astrophysics Data System (ADS)

    Demirel, M. C.; Booij, M. J.; Hoekstra, A. Y.

    2015-01-01

    This paper investigates the skill of 90-day low-flow forecasts using two conceptual hydrological models and one data-driven model based on Artificial Neural Networks (ANNs) for the Moselle River. The three models, i.e. HBV, GR4J and ANN-Ensemble (ANN-E), all use forecasted meteorological inputs (precipitation P and potential evapotranspiration PET), whereby we employ ensemble seasonal meteorological forecasts. We compared low-flow forecasts for five different cases of seasonal meteorological forcing: (1) ensemble P and PET forecasts; (2) ensemble P forecasts and observed climate mean PET; (3) observed climate mean P and ensemble PET forecasts; (4) observed climate mean P and PET and (5) zero P and ensemble PET forecasts as input for the models. The ensemble P and PET forecasts, each consisting of 40 members, reveal the forecast ranges due to the model inputs. The five cases are compared for a lead time of 90 days based on model output ranges, whereas the models are compared based on their skill of low-flow forecasts for varying lead times up to 90 days. Before forecasting, the hydrological models are calibrated and validated for a period of 30 and 20 years respectively. The smallest difference between calibration and validation performance is found for HBV, whereas the largest difference is found for ANN-E. From the results, it appears that all models are prone to over-predict runoff during low-flow periods using ensemble seasonal meteorological forcing. The largest range for 90-day low-flow forecasts is found for the GR4J model when using ensemble seasonal meteorological forecasts as input. GR4J, HBV and ANN-E under-predicted 90-day-ahead low flows in the very dry year 2003 without precipitation data. The results of the comparison of forecast skills with varying lead times show that GR4J is less skilful than ANN-E and HBV. Overall, the uncertainty from ensemble P forecasts has a larger effect on seasonal low-flow forecasts than the uncertainty from ensemble PET

  6. Climate and hydrological uncertainties in projections of flood and low-flows in France

    NASA Astrophysics Data System (ADS)

    Sauquet, E.; Vidal, J.-P.; Perrin, C.; Bourgin, P.-Y.; Chauveau, M.; Chazot, S.

    2012-04-01

    Changes in river flows are associated with different types of uncertainties, due to an imperfect knowledge of both future climate and rainfall-runoff processes. Due to computational constraints, impact and adaptation studies unfortunately cannot always afford to perform a detailed analysis of all these uncertainties. In that case, the modelling efforts have to focus on the most relevant source of uncertainty in order to provide the best estimate of the overall uncertainty. As part of the national Explore2070 project, the present study thus aims at assessing the hierarchy of uncertainties in changes on river flow extremes at the scale of France. Amongst all possible sources of uncertainties, two are here considered: (1) the uncertainty in General Circulation Model (GCM) configuration, with 7 different models that adequately sample the range of changes as projected by the GCMs used in the IPCC AR4 over France, and (2) the uncertainty in hydrological model structure, with 2 quite different models: GR4J (Perrin et al., 2003), a lumped conceptual model, and Isba-Modcou (Habets et al., 2008), a suite of a land surface scheme and a distributed hydrogeological model. The hydrological models have been run at more than 1500 locations in France over the 1961-1990 baseline period with forcings from both the Safran near-surface atmospheric reanalysis (Vidal et al., 2010) and the GCM control runs downscaled with a weather type method (Boé et al., 2006), and over the 2046-2065 period with forcings from all downscaled GCM runs under the A1B emissions scenario. Various high flow indices (annual maximum daily flow with return period of 10 and 20 years, the daily flow value exceeded 10% of the time) and low flow indices (annual minimum monthly flow with a 5-year return period, annual minimum 10-day mean flow with a 2-year return period, the daily flow value exceeded 95% of the time) as well as seasonality indices have been computed for both periods. An analysis of variance has been

  7. Modeling low-flow bedrock springs providing ecological habitats with climate change scenarios

    NASA Astrophysics Data System (ADS)

    Levison, J.; Larocque, M.; Ouellet, M. A.

    2014-07-01

    Groundwater discharge areas, including low-flow bedrock aquifer springs, are ecologically important and can be impacted by climate change. The development of and results from a groundwater modeling study simulating fractured bedrock spring flow are presented. This was conducted to produce hydrological data for an ecohydrological study of an endangered species, Allegheny Mountain Dusky Salamanders (Desmognathus ochrophaeus), in southern Quebec, Canada. The groundwater modeling approach in terms of scale and complexity was strongly driven by the need to produce hydrological data for the related ecohydrological modeling. Flows at four springs at different elevations were simulated for recent past conditions (2006-2010) and for reference (1971-2000) and future (2041-2070) periods using precipitation and temperature data from ten climate scenarios. Statistical analyses of spring flow parameters including activity periods and duration of flow were conducted. Flow rates for the four simulated springs, located at different elevations, are predicted to increase between 2% and 46% and will be active (flowing) 1-2% longer in the future. A significant change (predominantly an increase) looking at the seasonality of the number of active days occurs in the winter (2-4.9%) and spring seasons (-0.6-6.5%). Greatest flow rates were produced from springs at elevations where sub-horizontal fractures intersect the ground surface. These results suggest an intensification of the spring activity at the study site in context of climate change by 2050, which provides a positive habitat outlook for the endangered salamanders residing in the springs for the future.

  8. Temporal and spatial patterns of extreme low flows and effects on stream ecosystems in Otago, New Zealand

    NASA Astrophysics Data System (ADS)

    Caruso, B. S.

    2002-02-01

    The temporal and spatial patterns of summer extreme low flows and effects on stream ecosystems were evaluated throughout the Otago Region of the South Island of New Zealand during a severe drought in 1998-1999. Flows, water quality, and aquatic biology were monitored bimonthly at 12 locations as part of a long-term regional monitoring programme and results were evaluated and compared among summer 1998-1999 and all previous summers, as well as among three major subregions. Flows during the drought were extremely low for prolonged periods in many locations, particularly in North Otago. At most sites temperatures were slightly higher for a longer period than during other summers. In predominantly agricultural/pastoral catchments, widespread bacterial contamination of streams occurred due to increased livestock use of watercourses and decreased dilution during low flows. Concentrations of other contaminants derived from non-point sources, including nitrogen, phosphorus, and sediment, decreased in many locations due to the lack of rainfall and runoff events. Electrical conductivity generally increased as a result of the lack of dilution and increased evaporation and groundwater inputs. Overall water quality was worst in agricultural catchments in South Otago, and returned to conditions prior to the low flows by late autumn in most areas. The diversity of benthic macroinvertebrate communities and number of sensitive taxa decreased somewhat in many locations, but the magnitude and duration of these effects were not great. Differences between summer 1998-1999 and other periods, and among subregions, were not significant. Although some differences in low flows and effects on stream ecosystems across a range of landscapes and catchments can occur, the rapid recovery of water quality and benthic macroinvertebrates in most locations indicates that many streams are resilient to extreme low flows and drought with minor long-term effects.

  9. The effects of drainage basin geomorphometry on minimum low flow discharge: the study of small watershed in Kelang River Valley in Peninsular Malaysia.

    PubMed

    Yunus, Ahmad Jailani Muhamed; Nakagoshi, Nobukazu; Salleh, Khairulmaini Osman

    2003-03-01

    This study investigate the relationships between geomorphometric properties and the minimum low flow discharge of undisturbed drainage basins in the Taman Bukit Cahaya Seri Alam Forest Reserve, Peninsular Malaysia. The drainage basins selected were third-order basins so as to facilitate a common base for sampling and performing an unbiased statistical analyses. Three levels of relationships were observed in the study. Significant relationships existed between the geomorphometric properties as shown by the correlation network analysis; secondly, individual geomorphometric properties were observed to influence minimum flow discharge; and finally, the multiple regression model set up showed that minimum flow discharge (Q min) was dependent of basin area (AU), stream length (LS), maximum relief (Hmax), average relief (HAV) and stream frequency (SF). These findings further enforced other studies of this nature that drainage basins were dynamic and functional entities whose operations were governed by complex interrelationships occurring within the basins. Changes to any of the geomorphometric properties would influence their role as basin regulators thus influencing a change in basin response. In the case of the basin's minimum low flow, a change in any of the properties considered in the regression model influenced the "time to peak" of flow. A shorter time period would mean higher discharge, which is generally considered the prerequisite to flooding. This research also conclude that the role of geomorphometric properties to control the water supply within the stream through out the year even though during the drought and less precipitations months. Drainage basins are sensitive entities and any deteriorations involve will generate reciprocals and response to the water supply as well as the habitat within the areas. PMID:12765268

  10. Continuous high-energy low-flow-rate enteral support: a panoramic review of 1000 cases.

    PubMed

    Levy, E; Huguet, C; Parc, R; Ollivier, J M; Goldberg, J; Loygue, J

    1985-01-01

    One thousand intensive care digestive surgical cases are reviewed concerning continuous low-flow-rate enteral support (CLFRES), using Nutripompe: 607 males and 393 females, average age 51 years. The average duration of CLFRES is 21.5 days +/- 13, range 4 to 180 days. CLFRES was used postoperatively in 76 per cent, preoperatively in 10 per cent, and pre- and postoperatively in 14 per cent of cases, respectively. The enteral support route was 63 per cent nasogastric, 20 per cent gastrostomy and 17 per cent jejunostomy. Five hundred and ten patients required extensive digestive surgery with temporary exclusions. More than 100 patients with either temporary enterostomies or enterocutaneous fistulas have had continuous reinstillation of digestive chyme (CRDC) associated with their intensive care unit treatment management. CRDC in the lower end of an enterostomy has shown a specific retrograde inhibitory effect on the upper digestive secretions, particularly on the intestinal secretions during pathologies associated with one or several interruptions of the continuity of the gastrointestinal tract. This technique and its physiological implications were discussed. The principal pathologies in this important study group are: severe digestive fistulas, 24 per cent; acute diffuse peritonitis, 18 per cent; acute enterocolitis, 14 per cent; digestive tumours, 35 per cent; and acute necrotizing haemorrhagic pancreatitis, 9 per cent. A comparative analysis of nutritional energy nitrogen requirement was presented in view of the cancer, the septic, and the non-cancer non-septic patient groups. Enteral support nutritional solutions were primarily mixed non-degraded food, 70 per cent, and semi-elemental diets, 30 per cent. Certain pathology groups required variations in protein and lipid percentage. An up-to-date evaluation of nutritive formulas based on small peptides in normal and small bowel postoperative patients was discussed. Four CLFRES administration programmes were discussed

  11. Effects of Watershed Land Use and Geomorphology on Stream Low Flows During Severe Drought Conditions in the Southern Blue Ridge Mountains, Georgia and North Carolina, United States

    EPA Science Inventory

    Land use and physiographic variability influence stream low flows, yet their interactions and relative influence remain unresolved. Our objective was to assess the influence of land use and watershed geomorphic characteristics on low-flow variability in the southern Blue Ridge Mo...

  12. Increasing synchrony of high temperature and low flow in western North American streams: double trouble for coldwater biota?

    USGS Publications Warehouse

    Arismendi, Ivan; Safeeq, Mohammad; Johnson, Sherri L.; Dunham, Jason B.; Haggerty, Roy

    2013-01-01

    Flow and temperature are strongly linked environmental factors driving ecosystem processes in streams. Stream temperature maxima (Tmax_w) and stream flow minima (Qmin) can create periods of stress for aquatic organisms. In mountainous areas, such as western North America, recent shifts toward an earlier spring peak flow and decreases in low flow during summer/fall have been reported. We hypothesized that an earlier peak flow could be shifting the timing of low flow and leading to a decrease in the interval between Tmax_w and Qmin. We also examined if years with extreme low Qmin were associated with years of extreme high Tmax_w. We tested these hypotheses using long32 term data from 22 minimally human-influenced streams for the period 1950-2010. We found trends toward a shorter time lag between Tmax_w and Qmin over time and a strong negative association between their magnitudes. Our findings show that aquatic biota may be increasingly experiencing narrower time windows to recover or adapt between these extreme events of low flow and high temperature. This study highlights the importance of evaluating multiple environmental drivers to better gauge the effects of the recent climate variability in freshwaters.

  13. Evaluation of two low-flow releases from Big Tujunga Reservoir, Los Angeles County, California, 2003

    USGS Publications Warehouse

    Mendez, Gregory O.

    2005-01-01

    Since 1973, the Santa Ana Sucker (Catostomus santaanae) has been listed as a threatened species under the Endangered Species Act. The Lower Big Tujunga Creek, in Los Angeles County, is one of the areas in southern California where the Santa Ana Sucker is still present. This study was designed to assess two flow releases from Big Tujunga Dam that may contribute to favorable habitat conditions for the Santa Ana Sucker. It is important for the Santa Ana Sucker's survival that pools in the lower reach of the study area are replenished periodically. The focus of the study area was on the Lower Big Tujunga Creek within a reach extending approximately 6 miles downstream from the Big Tujunga Reservoir. Six sites were established from the Big Tujunga Dam to Delta Flats day-use area for data collection. This report describes the study design, discharge measurements, and the flow data collected from the two releases. Two scheduled flows (phases 1 and 2) were released from the Big Tujunga Reservoir in August and September 2003. During the first phase, which lasted 50 hours, travel times from the dam to four sites downstream were determined. Arrival times at the four sites were determined on the basis of temperature data. Travel time from the dam to site 6 (the furthest downstream site) was about 51.5 hours. Travel times for subreaches were 3 hours from site 1 to site 2, 6.5 hours from site 2 to site 3, almost 18 hours from site 3 to site 4, and 24 hours from site 4 to site 6. The temperature probe at site 5 was destroyed, and thus the arrival time could not be estimated. A probe that measures stage was placed in one of the many pools downstream from site 4 to evaluate a typical pool response to a low-flow release. Also, discharge measurements were taken at four sites along the study reach. In phase 2, which lasted 5 days (121 hours), flow losses along the 6-mile reach were analyzed. Losses were estimated by measuring difference in flow from the dam to sites 3, 4, 5, and 6

  14. Median and Low-Flow Characteristics for Streams under Natural and Diverted Conditions, Northeast Maui, Hawaii

    USGS Publications Warehouse

    Gingerich, Stephen B.

    2005-01-01

    Flow-duration statistics under natural (undiverted) and diverted flow conditions were estimated for gaged and ungaged sites on 21 streams in northeast Maui, Hawaii. The estimates were made using the optimal combination of continuous-record gaging-station data, low-flow measurements, and values determined from regression equations developed as part of this study. Estimated 50- and 95-percent flow duration statistics for streams are presented and the analyses done to develop and evaluate the methods used in estimating the statistics are described. Estimated streamflow statistics are presented for sites where various amounts of streamflow data are available as well as for locations where no data are available. Daily mean flows were used to determine flow-duration statistics for continuous-record stream-gaging stations in the study area following U.S. Geological Survey established standard methods. Duration discharges of 50- and 95-percent were determined from total flow and base flow for each continuous-record station. The index-station method was used to adjust all of the streamflow records to a common, long-term period. The gaging station on West Wailuaiki Stream (16518000) was chosen as the index station because of its record length (1914-2003) and favorable geographic location. Adjustments based on the index-station method resulted in decreases to the 50-percent duration total flow, 50-percent duration base flow, 95-percent duration total flow, and 95-percent duration base flow computed on the basis of short-term records that averaged 7, 3, 4, and 1 percent, respectively. For the drainage basin of each continuous-record gaged site and selected ungaged sites, morphometric, geologic, soil, and rainfall characteristics were quantified using Geographic Information System techniques. Regression equations relating the non-diverted streamflow statistics to basin characteristics of the gaged basins were developed using ordinary-least-squares regression analyses. Rainfall

  15. Evaluation of a novel helium ionization detector within the context of (low-)flow modulation comprehensive two-dimensional gas chromatography.

    PubMed

    Franchina, Flavio A; Maimone, Mariarosa; Sciarrone, Danilo; Purcaro, Giorgia; Tranchida, Peter Q; Mondello, Luigi

    2015-07-10

    The present research is focused on the use and evaluation of a novel helium ionization detector, defined as barrier discharge ionization detector (BID), within the context of (low-)flow modulation comprehensive two-dimensional gas chromatography (FM GC×GC). The performance of the BID device was compared to that of a flame ionization detector (FID), under similar FM GC×GC conditions. Following development and optimization of the FM GC×GC method, the BID was subjected to fine tuning in relation to acquisition frequency and discharge flow. Moreover, the BID performance was measured and compared to that of the FID, in terms of extra-column band broadening, sensitivity and dynamic range. The comparative study was carried out by using standard compounds belonging to different chemical classes, along with a sample of diesel fuel. Advantages and disadvantages of the BID system, also within the context of FM GC×GC, are critically discussed. In general, the BID system was characterized by a more limited dynamic range and increased sensitivity, compared to the FID. Additionally, BID and FID contribution to band broadening was found to be similar under the operational conditions applied. Particular attention was devoted to the behaviour of the FM GC×GC-BID system toward saturated and aromatic hydrocarbons, for a possible future use in the field of mineral-oil food contamination research. PMID:26032893

  16. Low-flow water-quality characterization of the Gore Creek watershed, upper Colorado River basin, Colorado, August 1996

    USGS Publications Warehouse

    Wynn, Kirby H.; Spahr, Norman E.

    1998-01-01

    sampling is needed to determine the distribution and sources of water-quality constituents at one point in time. In August 1996, a low-flow synoptic sampling for analyses of water-quality properties and constituents at sites in the Gore Creek watershed was done by the U.S. Geological Survey, in cooperation with the Town of Vail, Eagle River Water and Sanitation District, Upper Eagle River Water Authority, and Northwest Colorado Council of Governments, to evaluate the water quality of Gore Creek. The August low-flow period can be important from water-quality and stream ecology perspectives. There is less water available to dilute any contaminants entering the streams, and stream temperatures are highest during August. Physical habitat for aquatic plants and animals is smaller than during most other times of the year. To address these more extreme water-quality and ecological conditions, the synoptic sampling was conducted during the summer low-flow period. Specific objectives of this sampling included: 1. Establish a current data set representing the spatial characteristics of low-flow water-quality conditions in the Gore Creek watershed, and 2. Develop some understanding of land-use and water-quality relations in the watershed. This fact sheet presents hydrologic background information and an analysis of general water-quality properties and constituents, trace elements, and nutrients collected in water samples during low-flow synoptic sampling of the Gore Creek watershed. The U.S. Geological Survey also is conducting a study of the algae and macroinvertebrate communities and physical habitat of streams in the Gore Creek watershed during low flow. This study is designed to provide information about land-use and stream ecology relations in the watershed.

  17. Separation of Changes in Hydroclimatic and Basin Controls on Late-Summer Low Flow in British Columbia, Canada

    NASA Astrophysics Data System (ADS)

    Stahl, K.; Moore, R. D.; Allen, D. M.; Whitfield, P. H.

    2009-12-01

    For catchments in the Pacific Northwest of North America with minimal or no glacier cover, the summer period is typically dominated by low flows associated with the relatively warm, dry summers in that region. In recent years summer low flow has become more critical in terms of water use and fisheries, and there is increasing concern regarding effects of future climate change. In particular, it is expected that earlier snowmelt timing in spring causes longer recession periods and consequently lower streamflow during late summer. This study examined the sensitivity of late summer flows of 153 ‘unregulated’ rivers over the period 1976-2003 to hydroclimatic influences using trend tests accounting for exogenous variables by regression. Regression models were fitted using simultaneous and lagged variables of precipitation and timing and magnitude of snowmelt. The residuals were tested for trends and serial correlation to assess potential secondary influences such as long-term groundwater storage changes or mid-term changes in evapotranspiration. The decrease in September flows found across most of the region is broadly consistent with a decline in September precipitation. The most important control on August flows for all streamflow regimes is August precipitation. The influence of lagged variables including snowmelt timing varies. Rain-dominated and hybrid catchments along the coast tended to have positive trends in their residuals in August, suggesting an increasing trend in groundwater storage. Snowmelt dominated catchments show varied trends but the runs test detected a substantial number of stations with non-random residuals, suggesting mid-term secondary influences possibly associated with evapotranspiration changes due to progressive forest harvesting. This regional study greatly improves the understanding of the hydroclimatic influences on extreme summer low flow in the region. Results suggest that (the less predictable) summer climate is a larger influence

  18. Preservation of canine myocardial high-energy phosphates during low-flow ischemia with modification of hemoglobin–oxygen affinity

    PubMed Central

    Weiss, Robert G.; Mejia, Marco A.; Kass, David A.; DiPaula, Anthony F.; Becker, Lewis C.; Gerstenblith, Gary; Chacko, V.P.

    1999-01-01

    Conventional approaches for the treatment of myocardial ischemia increase coronary blood flow or reduce myocardial demand. To determine whether a rightward shift in the hemoglobin–oxygen saturation curve would reduce the metabolic and contractile effects of a myocardial oxygen-supply imbalance, we studied the impact of a potent synthetic allosteric modifier of hemoglobin–oxygen affinity, a 2-[4-[[(3,5-disubstituted anilino)carbonyl]methyl] phenoxy] -2-methylproprionic acid derivative (RSR13), during low-flow ischemia. Changes in myocardial high-energy phosphate levels and pH were studied by 31P nuclear magnetic resonance (NMR) spectroscopy in 12 open-chest dogs randomized to receive RSR13 or vehicle control during a reversible reduction of left anterior descending (LAD) coronary artery blood flow. Changes in cardiac metabolites and regional ventricular function studied by pressure segment–length relations were also investigated in additional animals before and after RSR13 administration during low-flow LAD ischemia. The intravenous administration of RSR13 before ischemia resulted in a substantial increase in the mean hemoglobin p50 and attenuated the decline in cardiac creatine phosphate/adenosine triphosphate (PCr/ATP), percent PCr, and pH during ischemia without a change in regional myocardial blood flow, heart rate, or systolic blood pressure. RSR13 given after the onset of low-flow ischemia also improved cardiac PCr/ATP ratios and regional function as measured by fractional shortening and regional work. Thus, synthetic allosteric reduction in hemoglobin–oxygen affinity may be a new and important therapeutic strategy to ameliorate the metabolic and functional consequences of cardiac ischemia. J. Clin. Invest. 103:739–746 (1999) PMID:10074492

  19. Preservation of canine myocardial high-energy phosphates during low-flow ischemia with modification of hemoglobin-oxygen affinity.

    PubMed

    Weiss, R G; Mejia, M A; Kass, D A; DiPaula, A F; Becker, L C; Gerstenblith, G; Chacko, V P

    1999-03-01

    Conventional approaches for the treatment of myocardial ischemia increase coronary blood flow or reduce myocardial demand. To determine whether a rightward shift in the hemoglobin-oxygen saturation curve would reduce the metabolic and contractile effects of a myocardial oxygen-supply imbalance, we studied the impact of a potent synthetic allosteric modifier of hemoglobin-oxygen affinity, a 2-[4-[[(3,5-disubstituted anilino)carbonyl]methyl] phenoxy] -2-methylproprionic acid derivative (RSR13), during low-flow ischemia. Changes in myocardial high-energy phosphate levels and pH were studied by 31P nuclear magnetic resonance (NMR) spectroscopy in 12 open-chest dogs randomized to receive RSR13 or vehicle control during a reversible reduction of left anterior descending (LAD) coronary artery blood flow. Changes in cardiac metabolites and regional ventricular function studied by pressure segment-length relations were also investigated in additional animals before and after RSR13 administration during low-flow LAD ischemia. The intravenous administration of RSR13 before ischemia resulted in a substantial increase in the mean hemoglobin p50 and attenuated the decline in cardiac creatine phosphate/adenosine triphosphate (PCr/ATP), percent PCr, and pH during ischemia without a change in regional myocardial blood flow, heart rate, or systolic blood pressure. RSR13 given after the onset of low-flow ischemia also improved cardiac PCr/ATP ratios and regional function as measured by fractional shortening and regional work. Thus, synthetic allosteric reduction in hemoglobin-oxygen affinity may be a new and important therapeutic strategy to ameliorate the metabolic and functional consequences of cardiac ischemia. PMID:10074492

  20. Low Flow Vortex Shedding Flow Meter for Hypergolics/all Media

    NASA Technical Reports Server (NTRS)

    Thinh, Ngo Dinh

    1991-01-01

    A family of vortex shedding flow meters, for measurement of hypergol flows, was designed and fabricated. The test loops to evaluate the flow meters for water flow, as well as Freon -113 flow which simulates the hypergolic fluids, were modified and constructed to utilize a pump system which has an output capacity of 200 gpm. Test runs were conducted on the small 1/2 inch model with Freon 113 and on the larger models with water. Results showed that the linearity between the frequency of the vortices and the flow rate of the fluids was very close to that of the turbine flow meter. It is suggested that the vortex shedding flow meter is a possible replacement for the existing turbine type.

  1. FishMORPH - An agent-based model to predict salmonid growth and distribution responses under natural and low flows

    PubMed Central

    Phang, S. C.; Stillman, R. A.; Cucherousset, J.; Britton, J. R.; Roberts, D.; Beaumont, W. R. C.; Gozlan, R. E.

    2016-01-01

    Predicting fish responses to modified flow regimes is becoming central to fisheries management. In this study we present an agent-based model (ABM) to predict the growth and distribution of young-of-the-year (YOY) and one-year-old (1+) Atlantic salmon and brown trout in response to flow change during summer. A field study of a real population during both natural and low flow conditions provided the simulation environment and validation patterns. Virtual fish were realistic both in terms of bioenergetics and feeding. We tested alternative movement rules to replicate observed patterns of body mass, growth rates, stretch distribution and patch occupancy patterns. Notably, there was no calibration of the model. Virtual fish prioritising consumption rates before predator avoidance replicated observed growth and distribution patterns better than a purely maximising consumption rule. Stream conditions of low predation and harsh winters provide ecological justification for the selection of this behaviour during summer months. Overall, the model was able to predict distribution and growth patterns well across both natural and low flow regimes. The model can be used to support management of salmonids by predicting population responses to predicted flow impacts and associated habitat change. PMID:27431787

  2. FishMORPH - An agent-based model to predict salmonid growth and distribution responses under natural and low flows.

    PubMed

    Phang, S C; Stillman, R A; Cucherousset, J; Britton, J R; Roberts, D; Beaumont, W R C; Gozlan, R E

    2016-01-01

    Predicting fish responses to modified flow regimes is becoming central to fisheries management. In this study we present an agent-based model (ABM) to predict the growth and distribution of young-of-the-year (YOY) and one-year-old (1+) Atlantic salmon and brown trout in response to flow change during summer. A field study of a real population during both natural and low flow conditions provided the simulation environment and validation patterns. Virtual fish were realistic both in terms of bioenergetics and feeding. We tested alternative movement rules to replicate observed patterns of body mass, growth rates, stretch distribution and patch occupancy patterns. Notably, there was no calibration of the model. Virtual fish prioritising consumption rates before predator avoidance replicated observed growth and distribution patterns better than a purely maximising consumption rule. Stream conditions of low predation and harsh winters provide ecological justification for the selection of this behaviour during summer months. Overall, the model was able to predict distribution and growth patterns well across both natural and low flow regimes. The model can be used to support management of salmonids by predicting population responses to predicted flow impacts and associated habitat change. PMID:27431787

  3. Laminated metal composite formed from low flow stress layers and high flow stress layers using flow constraining elements and making same

    DOEpatents

    Syn, C.K.; Lesuer, D.R.

    1995-07-04

    A laminated metal composite of low flow stress layers and high flow stress layers is described which is formed using flow constraining elements, preferably in the shape of rings, individually placed around each of the low flow stress layers while pressure is applied to the stack to bond the layers of the composite together, to thereby restrain the flow of the low flow stress layers from the stack during the bonding. The laminated metal composite of the invention is made by the steps of forming a stack of alternate layers of low flow stress layers and high flow stress layers with each layer of low flow stress material surrounded by an individual flow constraining element, such as a ring, and then applying pressure to the top and bottom surfaces of the resulting stack to bond the dissimilar layers together, for example, by compression rolling the stack. In a preferred embodiment, the individual flow constraining elements surrounding the layers of low flow stress material are formed of a material which may either be the same material as the material comprising the high flow stress layers, or have similar flow stress characteristics to the material comprising the high flow stress layers. Additional sacrificial layers may be added to the top and bottom of the stack to avoid damage to the stack during the bonding step; and these additional layers may then be removed after the bonding step. 5 figs.

  4. Laminated metal composite formed from low flow stress layers and high flow stress layers using flow constraining elements and making same

    DOEpatents

    Syn, Chol K.; Lesuer, Donald R.

    1995-01-01

    A laminated metal composite of low flow stress layers and high flow stress layers is described which is formed using flow constraining elements, preferably in the shape of rings, individually placed around each of the low flow stress layers while pressure is applied to the stack to bond the layers of the composite together, to thereby restrain the flow of the low flow stress layers from the stack during the bonding. The laminated metal composite of the invention is made by the steps of forming a stack of alternate layers of low flow stress layers and high flow stress layers with each layer of low flow stress material surrounded by an individual flow constraining element, such as a ring, and then applying pressure to the top and bottom surfaces of the resulting stack to bond the dissimilar layers together, for example, by compression rolling the stack. In a preferred embodiment, the individual flow constraining elements surrounding the layers of low flow stress material are formed of a material which may either be the same material as the material comprising the high flow stress layers, or have similar flow stress characteristics to the material comprising the high flow stress layers. Additional sacrificial layers may be added to the top and bottom of the stack to avoid damage to the stack during the bonding step; and these additional layers may then be removed after the bonding step.

  5. Availability and distribution of low flow in Anahola Stream, Kauaʻi, Hawaiʻi

    USGS Publications Warehouse

    Cheng, Chui Ling; Wolff, Reuben H.

    2012-01-01

    Anahola Stream is a perennial stream in northeast Kauaʻi, Hawaiʻi, that supports agricultural, domestic, and cultural uses within its drainage basin. Beginning in the late 19th century, Anahola streamflow was diverted by Makee Sugar Company at altitudes of 840 feet (upper intake) and 280 feet (lower intake) for irrigating sugarcane in the Keālia area. When sugarcane cultivation in the Keālia area ceased in 1988, part of the Makee Sugar Company’s surface-water collection system (Makee diversion system) in the Anahola drainage basin was abandoned. In an effort to better manage available surface-water resources, the State of Hawaiʻi Department of Hawaiian Home Lands is considering using the existing ditches in the Anahola Stream drainage basin to provide irrigation water for Native Hawaiian farmers in the area. To provide information needed for successful management of the surface-water resources, the U.S. Geological Survey investigated the availability and distribution of natural low flow in Anahola Stream and also collected low-flow data in Goldfish Stream, a stream that discharges into Kaneha Reservoir, which served as a major collection point for the Makee diversion system. Biological surveys of Anahola Stream were conducted as part of a study to determine the distribution of native and nonnative aquatic stream fauna. Results of the biological surveys indicated the presence of the following native aquatic species in Anahola Stream: ʻoʻopu ʻakupa (Sandwich Island sleeper) and ʻoʻopu naniha (Tear-drop goby) in the lower stream reaches surveyed; and ʻoʻopu nākea (Pacific river goby), ʻoʻopu nōpili (Stimpson’s goby), and ʻōpae kalaʻole (Mountain shrimp) in the middle and upper stream reaches surveyed. Nonnative aquatic species were found in all of the surveyed stream reaches along Anahola Stream. The availability and distribution of natural low flow were determined using a combination of discharge measurements made from February 2011 to May 2012

  6. Comparison of temporal trends in VOCs as measured with PDB samplers and low-flow sampling methods

    USGS Publications Warehouse

    Harte, P.T.

    2002-01-01

    Analysis of temporal trends in tetrachloroethylene (PCE) concentration determined by two sample techniques showed that passive diffusion bag (pdb) samplers adequately sample the large variation in PCE concentrations at the site. The slopes of the temporal trends in concentrations were comparable between the two techniques, and the pdb sample concentration generally reflected the instantaneous concentration sampled by the low-flow technique. Thus, the pdb samplers provided an appropriate sampling technique for PCE at these wells. One or two wells did not make the case for widespread application of pdb samples at all sites. However, application of pdb samples in some circumstances was appropriate for evaluating temporal and spatial variations in VOC concentrations, thus, should be considered as a useful tool in hydrogeology.

  7. Emergency Endovascular Treatment of an Acute Traumatic Rupture of the Thoracic Aorta Complicated by a Distal Low-Flow Syndrome

    SciTech Connect

    Bruninx, Guy; Wery, Didier; Dubois, Eric; El Nakadi, Badih; Dueren, Eric van; Verhelst, Guy; Delcour, Christian

    1999-11-15

    We report the case of a patient who suffered major trauma following a motorcycle accident that resulted in multiple fractures, bilateral hemopneumothorax, pulmonary contusions, and an isthmic rupture of the aorta with a pseudoaneurysm compressing the descending aorta. This compression was responsible for distal hypotension and low flow, leading to acute renal insufficiency and massive rhabdomyolysis. Due to the critical clinical status of the patient, which prevented any type of open thoracic surgery, endovascular treatment was performed. An initial stent-graft permitted alleviation of the compression and the re-establishment of normal hemodynamic conditions, but its low position did not allow sufficient coverage of the rupture. A second stent-graft permitted total exclusion of the pseudoaneurysm while preserving the patency of the left subclavian artery.

  8. Applying Physically Representative Watershed Modelling to Assess Peak and Low Flow Response to Timber Harvest: Application for Watershed Assessments

    NASA Astrophysics Data System (ADS)

    MacDonald, R. J.; Anderson, A.; Silins, U.; Craig, J. R.

    2014-12-01

    Forest harvesting, insects, disease, wildfire, and other disturbances can combine with climate change to cause unknown changes to the amount and timing of streamflow from critical forested watersheds. Southern Alberta forest and alpine areas provide downstream water supply for agriculture and water utilities that supply approximately two thirds of the Alberta population. This project uses datasets from intensely monitored study watersheds and hydrological model platforms to extend our understanding of how disturbances and climate change may impact various aspects of the streamflow regime that are of importance to downstream users. The objectives are 1) to use the model output of watershed response to disturbances to inform assessments of forested watersheds in the region, and 2) to investigate the use of a new flexible modelling platform as a tool for detailed watershed assessments and hypothesis testing. Here we applied the RAVEN hydrological modelling framework to quantify changes in key hydrological processes driving peak and low flows in a headwater catchment along the eastern slopes of the Canadian Rocky Mountains. The model was applied to simulate the period from 2006 to 2011 using data from the Star Creek watershed in southwestern Alberta. The representation of relevant hydrological processes was verified using snow survey, meteorological, and vegetation data collected through the Southern Rockies Watershed Project. Timber harvest scenarios were developed to estimate the effects of cut levels ranging from 20 to 100% over a range of elevations, slopes, and aspects. We quantified changes in the timing and magnitude of low flow and high flow events during the 2006 to 2011 period. Future work will assess changes in the probability of low and high flow events using a long-term meteorological record. This modelling framework enables relevant processes at the watershed scale to be accounted in a physically robust and computational efficient manner. Hydrologic

  9. Comparison of pesticide concentrations in streams at low flow in six metropolitan areas of the United States

    USGS Publications Warehouse

    Sprague, L.A.; Nowell, L.H.

    2008-01-01

    To examine the effect of urban development on pesticide concentrations in streams under low-flow conditions, water samples were collected at stream sites along an urban land use gradient in six environmentally heterogeneous metropolitan areas of the United States. In all six metropolitan areas, total insecticide concentrations generally increased significantly as urban land cover in the basin increased, regardless of whether the background land cover in the basins was agricultural, forested, or shrub land. In contrast, the response of total herbicide concentrations to urbanization varied with the environmental setting. In the three metropolitan areas with predominantly forested background land cover (Raleigh-Durham, NC, USA; Atlanta, GA, USA; Portland, OR, USA), total herbicide concentrations increased significantly with increasing urban land cover. In contrast, total herbicide concentrations were not significantly related to urban land cover in the three remaining metropolitan areas, where total herbicide concentrations appeared to be strongly influenced by agricultural as well as urban sources (Milwaukee-Green Bay, WI, USA; Dallas-Fort Worth, TX, USA), or by factors not measured in the present study, such as water management (Denver, CO, USA). Pesticide concentrations rarely exceeded benchmarks for protection of aquatic life, although these low-flow concentrations are likely to be lower than at other times, such as during peak pesticide-use periods, storm events, or irrigation discharge. Normalization of pesticide concentrations by the pesticide toxicity index - an index of relative potential toxicity - for fish and cladocerans indicated that the pesticides detected at the highest concentrations (herbicides in five of the six metropolitan areas) were not necessarily the pesticides with the greatest potential to adversely affect aquatic life (typically insecticides such as carbaryl, chlorpyrifos, diazinon, and fipronil). ?? 2008 SETAC.

  10. The “Little AVM”: A New Entity in High-flow versus Low-flow Vascular Malformations

    PubMed Central

    Stein, Michael; Guilfoyle, Regan; Courtemanche, Douglas J.; Moss, Wendy; Bucevska, Marija

    2014-01-01

    Background: Arteriovenous malformations (AVMs) are high-flow lesions with abnormal connections between arteries and veins without an intervening capillary bed. Infrequently, the radiographic diagnosis of a vascular lesion will not support the clinical diagnosis of an AVM. These “discrepant” lesions are not adequately captured within the current classification system and represent a treatment dilemma. The purpose of this study is to review our center’s experience with vascular malformations where incongruity in a patient’s clinical and radiographic presentation produces a diagnostic and therapeutic challenge. Methods: A retrospective chart review of patients with atypical AVM pre sen ta tions was performed. Parameters reviewed included patient history and demogra phics, clinical presentation, radiological imaging, and treatment modalities. Results: Over a 15-year period, we identified 7 cases of vascular malformations with discrepant clinical and radiological findings concerning flow characteristics. All patients were treated based on their radiological diagnosis and most were managed with sclerotherapy. No lesions evolved into a high-flow process, and there was no recurrence at a minimum of 24 months of follow-up. Conclusions: We have identified and described a unique subcategory of vascular malformations that have clinical features of high-flow malformations but radiological features of low-flow malformations. These lesions behave like low-flow malformations and should be treated as such. We propose that complex vascular malformations are best evaluated by both clinical and specialized diagnostic radiological means; the radiologic diagnoses should supplant what is found clinically, and ultimately treatment should be preferentially based on a radiological diagnosis. PMID:25426370

  11. Streamflow measurements, basin characteristics, and streamflow statistics for low-flow partial-record stations operated in Massachusetts from 1989 through 1996

    USGS Publications Warehouse

    Ries, Kernell G., III

    1999-01-01

    A network of 148 low-flow partial-record stations was operated on streams in Massachusetts during the summers of 1989 through 1996. Streamflow measurements (including historical measurements), measured basin characteristics, and estimated streamflow statistics are provided in the report for each low-flow partial-record station. Also included for each station are location information, streamflow-gaging stations for which flows were correlated to those at the low-flowpartial-record station, years of operation, and remarks indicating human influences of stream-flowsat the station. Three or four streamflow measurements were made each year for three years during times of low flow to obtain nine or ten measurements for each station. Measured flows at the low-flow partial-record stations were correlated with same-day mean flows at a nearby gaging station to estimate streamflow statistics for the low-flow partial-record stations. The estimated streamflow statistics include the 99-, 98-, 97-, 95-, 93-, 90-, 85-, 80-, 75-, 70-, 65-, 60-, 55-, and 50-percent duration flows; the 7-day, 10- and 2-year low flows; and the August median flow. Characteristics of the drainage basins for the stations that theoretically relate to the response of the station to climatic variations were measured from digital map data by use of an automated geographic information system procedure. Basin characteristics measured include drainage area; total stream length; mean basin slope; area of surficial stratified drift; area of wetlands; area of water bodies; and mean, maximum, and minimum basin elevation.Station descriptions and calculated streamflow statistics are also included in the report for the 50 continuous gaging stations used in correlations with the low-flow partial-record stations.

  12. Flow routing in the Susquehanna River Basin, Part II: Lowflow frequency characteristics of the Susquehanna River between Waverly, New York and Sunbury, Pennsylvania

    USGS Publications Warehouse

    Bingham, Donald L.

    1979-01-01

    The model errors, differences between model results and observed streamflow at gaged sites, are considered to be within reasonable limits and overall quality of simulated streamflow and low-flow frequency curves is considered good. (Woodard-USGS)

  13. Low flow fume hood

    DOEpatents

    Bell, Geoffrey C.; Feustel, Helmut E.; Dickerhoff, Darryl J.

    2002-01-01

    A fume hood is provided having an adequate level of safety while reducing the amount of air exhausted from the hood. A displacement flow fume hood works on the principal of a displacement flow which displaces the volume currently present in the hood using a push-pull system. The displacement flow includes a plurality of air supplies which provide fresh air, preferably having laminar flow, to the fume hood. The displacement flow fume hood also includes an air exhaust which pulls air from the work chamber in a minimally turbulent manner. As the displacement flow produces a substantially consistent and minimally turbulent flow in the hood, inconsistent flow patterns associated with contaminant escape from the hood are minimized. The displacement flow fume hood largely reduces the need to exhaust large amounts of air from the hood. It has been shown that exhaust air flow reductions of up to 70% are possible without a decrease in the hood's containment performance. The fume hood also includes a number of structural adaptations which facilitate consistent and minimally turbulent flow within a fume hood.

  14. Methods for estimating flow-duration curve and low-flow frequency statistics for ungaged locations on small streams in Minnesota

    USGS Publications Warehouse

    Ziegeweid, Jeffrey R.; Lorenz, David L.; Sanocki, Chris A.; Czuba, Christiana R.

    2015-01-01

    Equations developed in this study apply only to stream locations where flows are not substantially affected by regulation, diversion, or urbanization. All equations presented in this study will be incorporated into StreamStats, a web-based geographic information system tool developed by the U.S. Geological Survey. StreamStats allows users to obtain streamflow statistics, basin characteristics, and other information for user-selected locations on streams through an interactive map.

  15. From Mountains to Plains: The Hydrogeochemistry of the Boulder Creek Watershed, Colorado during High- and Low-Flow Conditions 2000

    NASA Astrophysics Data System (ADS)

    Verplanck, P. L.; Murphy, S. F.; McCleskey, R. B.; Barber, L. B.; Roth, D. A.

    2002-05-01

    A hydrogeochemical study of the Boulder Creek watershed was undertaken to evaluate natural and anthropogenic sources of solutes and the geochemical processes that affect stream chemistry. The Boulder Creek watershed, 1160 km{2}, is in the Front Range of the Rocky Mountains in Colorado and can be delineated into five physiographic/land use regions: the headwater region (elev. 4100 to 2600 m, tundra to pine/fir forest, Precambrian and Tertiary gneisses and plutons, sparse habitation), the mountain corridor (elev. 2600 to 1750 m, ponderosa pine, Precambrian and Tertiary gneisses and plutons, small mountain communities), the urban region (elev. 1750 to 1560 m, grassland, Mesozoic sedimentary units, City of Boulder), the wastewater-dominated reach (elev. 1560 to 1540 m, grassland, Mesozoic sedimentary units, sewage treatment plant effluent), and the agriculture region (elev. 1540 to 1480 m, grassland, Mesozoic sedimentary units, mixed urban and agricultural). Potential anthropogenic sources of solutes include: mining (hardrock and aggregate), septic systems, highway runoff, urban wastewater, and agricultural practices. A 70 km reach of Boulder Creek (16 sites) and its major inflows (13 sites) were sampled during high- and low-flow conditions in 2000. At all sites, discharge was measured or estimated, and water samples were analyzed for major and trace elements and organic carbon. At selected sites, analyses also included a suite of pesticides, pharmaceuticals, and wastewater-derived organic compounds and the strontium isotopic composition. Stream water in the headwater region is a dilute Ca-Mg-HCO3-SO4- water, and in the mountain corridor a slight increase in solutes was observed. Within the urban reach solute concentrations increased, with the most dramatic increase below the sewage treatment plant. Many constituents continue to increase in concentration through the urban/agriculture region. Similar trends were observed during high- and low-flow conditions with

  16. Low-flow, long-term air sampling under normal domestic activity to measure house dust mite and cockroach allergens.

    PubMed

    Park, Jung Won; Kim, Cheol Woo; Kang, Dae Bong; Lee, In Young; Choi, Soo Young; Yong, Tai-Soon; Shin, Dong Cheon; Kim, Kyu Earn; Hong, Chein-Soo

    2002-01-01

    Successful applications of air sampling for the quantification of exposure to indoor allergens have been reported, but its efficiency is still controversial. We evaluated whether the low-flow, long-term air sampling in normal domestic activity conditions can quantify the exposure of house dust mites (HDM) and cockroaches (CR) allergens or not. Airborne Der f 1 and Bla g 1 were captured with a personal air sampler in 25 bedrooms during normal domestic activity. Quantification of the major allergens in the reservoir dust and the extraction of the air sampler filters were done with two-site ELISA kits. Airborne Der f 1 was measured above the threshold level of detection in 15 houses (60%). Detection rate of airborne Der f 1 was significantly higher in those houses where D. farinae was microscopically found in the reservoir dusts (76.5% vs. 25%, chi 2 = 6.0, p = 0.014). Airborne Der f 1 was more frequently detected in the houses with higher Der f 1 (> or = 10 micrograms/g dust) in bedding reservoir dust than the other group (91% vs. 35.7%, chi 2 = 7.819, p = 0.005), and the median value of airborne Der f 1 was also significantly higher in that group (14.0 pg/m3 vs. below detection limit, p = 0.002). Airborne Der f 1 was significantly correlated with Der f 1 in bedding reservoir dust (r = 0.591, p < 0.01). Airborne Bla g 1 was measured with ELISA in 16 houses (64%), and it was more frequently detected in the houses where the CRs were captured by adhesive traps (91% vs. 57%, chi 2 = 3,484, p = 0.06). The median concentration of Bla g 1 in the filter was also higher in the houses with captured CRs (0.12 vs. 0.05 mU/m3, p = 0.06), but the level of Bla g 1 did not correlate with that of the bedding dusts or the floor dusts of kitchen. These results suggested that airborne HDM or CR allergens could be measured by low-flow, long-term air sampling, and that it might be one of appropriate modalities for evaluating personal exposure to HDM and CR allergens. PMID:12926189

  17. Concentrations, loads and yields of selected water-quality constituents during low flow and storm runoff from three watersheds at Fort Leavenworth, Kansas, May 1994 through September 1996

    USGS Publications Warehouse

    Rasmussen, P.P.

    1998-01-01

    A study of the effects of storm runoff from urban areas on water quality at Fort Leavenworth, Kansas, was conducted from May 1994 through September 1996. The purpose of this report is to present information to assess the current (1994-96) conditions and possible methods for anticipating future water-quality effects from storm runoff and changes in land use. Three sampling sites were established to monitor streamflow and water quality from three watersheds draining the study area. Streamflow was monitored continuously, and water-quality samples were collected during low-flow (12 samples) and storm-runoff (21 samples) conditions to determine mean annual constituent loads. Constituent concentrations for the most part were smallest during low flow with the exception of major ions, dissolved solids, and some nutrients. Concentrations of suspended solids and total recoverable metals at all three sites were much larger in storm-runoff samples than in low-flow samples--typically an order of magnitude larger than low-flow concentrations. Mean low-flow nutrient concentrations were either larger than or smaller than storm-runoff concentrations depending on the watershed. Total chloroform and total tetrachloroethylene were the only two volatile organic compounds detected, and acid-base/neutral organic compounds were not detected in any of the samples collected. Eight pesticides were detected in low-flow samples, and 15 pesticides were detected in storm-runoff samples. The only mean concentrations of the selected constituents in this study that exceeded either the U.S. Environmental Protection Agency's Maximum Contaminant Level or the Secondary Maximum Contaminant Level were dissolved solids and total recoverable iron and manganese.

  18. Hydrologic data from test wells and low-flow investigations in the middle reach of the Eagle River valley, Alaska; 1980-81

    USGS Publications Warehouse

    Deeter, Gary; George, R.S.

    1982-01-01

    Test wells and low-flow investigations in the Eagle River valley , Alaska, were used to evaluate the feasibility of developing ground water for a public supply. Aquifers capable of supplying large yield wells were not indicated in any of the drilling areas. The data include: results of low-flow seepage investigations at 22 river sites; geologic materials logs of eight test wells; water-quality data from two observation wells, two springs, and two river sites; and water level and temperature information for the observation wells and streams. (USGS)

  19. Single-Site Low-Flow Veno-Venous Extracorporeal Lung Support Does Not Influence Hemodynamic Monitoring by Transpulmonary Thermodilution.

    PubMed

    Redwan, Bassam; Ziegeler, Stephan; Freermann, Stefan; Meemann, Thomas; Semik, Michael; Dickgerber, Nicolas; Fischer, Stefan

    2016-01-01

    The application of extracorporeal lung support (ECLS) in patients with acute respiratory distress syndrome is a well-established concept. In patients receiving ECLS therapy, hemodynamic monitoring is often required. However, less is known about the effect of ECLS on hemodynamic measurements. In the present work, the influence of single-site low-flow veno-venous ECLS (LFVV-ECLS) on hemodynamic monitoring by transpulmonary thermodilution (TPTD) was prospectively investigated. Five consecutive patients undergoing single-site LFVV-ECLS for severe hypercapnic respiratory failure were included in this study. For single-site LFVV-ECLS, a 22 Fr twin-port double-lumen cannula was inserted percutaneously into the right jugular vein. Hemodynamic monitoring was performed using the Pulse index Continuous Cardiac Output system. Before ECLS initiation, baseline measurements of cardiac index, systemic vascular resistance, mean arterial pressure, and extravascular lung water (EVLW) were performed. During the first 3 days of ECLS therapy, repeated hemodynamic measurements at different ECLS flow rates were performed. No significant differences were seen in hemodynamic measurements. With respect to EVLW, a significant decrease over the duration of ECLS therapy was observed. This study demonstrates that LFVV-ECLS does not interfere with TPTD. It needs to be further studied if these findings also apply to other ECLS modes. PMID:27045969

  20. Thermal Solid Sample Introduction-Fast Gas Chromatography-Low Flow Ion Mobility Spectrometry as a field screening detection system.

    PubMed

    Hajialigol, Saeed; Ghorashi, Seyed Alireza; Alinoori, Amir Hossein; Torabpour, Amir; Azimi, Mehdi

    2012-12-14

    The potential of Thermal Solid Sample Introduction (TSSI)-Fast Gas Chromatography (GC)-Low Flow Ion Mobility Spectrometry (LF-IMS) having been designed and constructed in Engineering Research Center of Esfahan, detector group was investigated for chemical detection capabilities. Customizing the configuration of fast GC-IMS as a high technology, provides unique solutions for rapid detection of a broad range of chemical mixtures in many operational environments. TSSI configuration provides fast and easily applied method for direct detection with no additional sample preparation or extraction. The time required for total analysis, less than 265 s, was determined by the wide range of solid matrixes, including nitrate esters, nitroaromatics, and a nitramine. The fast extraction together with the short separation time limits degradation of the thermally labile compounds and decreases the peak widths, which results in larger peak intensities and a simultaneous improvement in detection limits. For signal-to-noise ratio equals to 5, the detection limits for instrument for TNT, DNT and RDX were attained 15, 10 and 50 ng/μl respectively. The combination of short analysis time and low detection limits make this instrument a potential candidate for field screening techniques. PMID:23141709

  1. RELAP5-3D Analysis of Pressure Perturbation at the Peach Bottom BWR During Low-Flow Stability Tests

    SciTech Connect

    Lombardi Costa, Antonella; Petruzzi, Alessandro; D'Auria, Francesco

    2006-07-01

    Experimental and theoretical studies about the BWR (Boiling Water Reactor) stability have been performed to design a stable core configuration. BWR instabilities can be caused by inter-dependencies between thermal-hydraulic and reactivity feedback parameters such as the void-coefficient, for example, during a pressure perturbation event. In the present work, the pressure perturbation is considered in order to study in detail this type of transient. To simulate this event, including the strong feedback effects between core neutronic and reactor thermal-hydraulics, and to verify core behavior and evaluate parameters related to safety, RELAP5-3D code has been used in the analyses. The simulation was performed making use of Peach Bottom-2 BWR data to predict the dynamics of a real reactor during this type of event. Stability tests were conducted in the Peach Bottom 2 BWR, in 1977, and were done along the low-flow end of the rated power-flow line, and along the power-flow line corresponding to minimum recirculation pump speed. The calculated results are herein compared against the available experimental data. (authors)

  2. Heavy metal discharges into Shasta Lake and Keswick reservoirs on the upper Sacramento River, California; a reconnaissance during low flow

    USGS Publications Warehouse

    Nordstrom, D. Kirk; Jenne, Everett A.; Averett, Robert C.

    1977-01-01

    Four out of seventeen streams entering the Shasta-Keswick Reservoir system in California contribute up to 94 percent of the heavy metal load into the upper Sacramento River under the low flow conditions which existed in the fall of 1974. Of these four streams, three contain acid mine drainage, with Spring Creek carrying more than 50 percent of the total load for every element analyzed except lead. The Pit River (the fourth stream) contains low concentrations of metals and has neutral pH values; but since it carries the greatest discharge, its computed loads also are high. The immediate danger to fishin the Shasta-Keswick region is not the contribution of acidity and toxic metals to the total load, but toxicity at the localized point of mixing where the acid streams mix with lake water. Zinc and cadmium, in addition to copper, are present in high concentrations for five of the seventeen streams and may exert significant synergistic effects. The presence of arsenic in some of the ore minerals suggests that it also may contribute to the toxicity of the mine drainage. (Woodard-USGS)

  3. Accuracy of thermodilution measurement of cardiac output in low flows applicable to feline and small canine patients.

    PubMed

    Dyson, D H; McDonnell, W N; Horne, J A

    1984-10-01

    A model system of feline or small canine cardiac output was used to produce known liquid flow rates in the range of 100 to 750 mL/min for comparison against a thermodilution technique of flow measurement. Thermal indicator size was decided by the thermal time concentration curve detected by the Edwards 9520A cardiac output computer. Ten consecutive readings for each flow were made. Regression analysis and Student's t-test were used to evaluate the results. The computer was found to give good correlation with the accurate flow measured by a graduated cylinder over a period of time (r = 0.99). An error of less than 7% overestimation of flow by thermodilution was found with flows greater than 200 mL/min (p less than 0.05). A significant error of more than 20% overestimation of the actual flow occurred with flows less than 200 mL/min (p less than 0.05). The Edwards 9520A computer was compared to the older Edwards 9510A model by averaged triplicate measurements at six different cardiac outputs in an anesthetized cat. The measurements were not significantly different (p less than 0.01). Thermodilution using an Edwards computer proves to be a promising tool in the measurement of low flows applicable to feline and small canine cardiac outputs. PMID:6509371

  4. Catastrophic shifts in the aquatic primary production revealed by a small low-flow section of tropical downstream after dredging.

    PubMed

    Marotta, H; Enrich-Prast, A

    2015-11-01

    Dredging is a catastrophic disturbance that directly affects key biological processes in aquatic ecosystems, especially in those small and shallow. In the tropics, metabolic responses could still be enhanced by the high temperatures and solar incidence. Here, we assessed changes in the aquatic primary production along a small section of low-flow tropical downstream (Imboassica Stream, Brazil) after dredging. Our results suggested that these ecosystems may show catastrophic shifts between net heterotrophy and autotrophy in waters based on three short-term stages following the dredging: (I) a strongly heterotrophic net primary production -NPP- coupled to an intense respiration -R- likely supported by high resuspended organic sediments and nutrients from the bottom; (II) a strongly autotrophic NPP coupled to an intense gross primary production -GPP- favored by the high nutrient levels and low solar light attenuation from suspended solids or aquatic macrophytes; and (III) a NPP near to the equilibrium coupled to low GPP and R rates following, respectively, the shading by aquatic macrophytes and high particulate sedimentation. In conclusion, changes in aquatic primary production could be an important threshold for controlling drastic shifts in the organic matter cycling and the subsequent silting up of small tropical streams after dredging events. PMID:26602334

  5. High-end climate change impact on European runoff and low flows - exploring the effects of forcing biases

    NASA Astrophysics Data System (ADS)

    Papadimitriou, Lamprini V.; Koutroulis, Aristeidis G.; Grillakis, Manolis G.; Tsanis, Ioannis K.

    2016-05-01

    Climate models project a much more substantial warming than the 2 °C target under the more probable emission scenarios, making higher-end scenarios increasingly plausible. Freshwater availability under such conditions is a key issue of concern. In this study, an ensemble of Euro-CORDEX projections under RCP8.5 is used to assess the mean and low hydrological states under +4 °C of global warming for the European region. Five major European catchments were analysed in terms of future drought climatology and the impact of +2 °C versus +4 °C global warming was investigated. The effect of bias correction of the climate model outputs and the observations used for this adjustment was also quantified. Projections indicate an intensification of the water cycle at higher levels of warming. Even for areas where the average state may not considerably be affected, low flows are expected to reduce, leading to changes in the number of dry days and thus drought climatology. The identified increasing or decreasing runoff trends are substantially intensified when moving from the +2 to the +4° of global warming. Bias correction resulted in an improved representation of the historical hydrology. It is also found that the selection of the observational data set for the application of the bias correction has an impact on the projected signal that could be of the same order of magnitude to the selection of the Global Climate Model (GCM).

  6. Sensitive analysis of low-flow parameters using the hourly hydrological model for two mountainous basins in Japan

    NASA Astrophysics Data System (ADS)

    Fujimura, Kazumasa; Iseri, Yoshihiko; Kanae, Shinjiro; Murakami, Masahiro

    2014-05-01

    Accurate estimation of low flow can contribute to better water resources management and also lead to more reliable evaluation of climate change impacts on water resources. In the early study, the nonlinearity of low flow related to the storage in the basin was suggested by Horton (1937) as the exponential function of Q=KSN, where Q is the discharge, S is the storage, K is a constant and N is the exponent value. In the recent study by Ding (2011) showed the general storage-discharge equation of Q = KNSN. Since the constant K is defined as the fractional recession constant and symbolized as Au by Ando et al. (1983), in this study, we rewrite this equation as Qg=AuNSgN, where Qg is the groundwater runoff and Sg is the groundwater storage. Although this equation was applied to a short-term runoff event of less than 14 hours using the unit hydrograph method by Ding, it was not yet applied for a long-term runoff event including low flow more than 10 years. This study performed a sensitive analysis of two parameters of the constant Au and exponent value N by using the hourly hydrological model for two mountainous basins in Japan. The hourly hydrological model used in this study was presented by Fujimura et al. (2012), which comprise the Diskin-Nazimov infiltration model, groundwater recharge and groundwater runoff calculations, and a direct runoff component. The study basins are the Sameura Dam basin (SAME basin) (472 km2) located in the western Japan which has variability of rainfall, and the Shirakawa Dam basin (SIRA basin) (205km2) located in a region of heavy snowfall in the eastern Japan, that are different conditions of climate and geology. The period of available hourly data for the SAME basin is 20 years from 1 January 1991 to 31 December 2010, and for the SIRA basin is 10 years from 1 October 2003 to 30 September 2013. In the sensitive analysis, we prepared 19900 sets of the two parameters of Au and N, the Au value ranges from 0.0001 to 0.0100 in steps of 0

  7. Frequency curves

    USGS Publications Warehouse

    Riggs, H.C.

    1968-01-01

    This manual describes graphical and mathematical procedures for preparing frequency curves from samples of hydrologic data. It also discusses the theory of frequency curves, compares advantages of graphical and mathematical fitting, suggests methods of describing graphically defined frequency curves analytically, and emphasizes the correct interpretations of a frequency curve.

  8. Sensitivity of Low Flow Simulations by the HBV-EC Hydrological Model to the Choice of Downscaling Algorithm, Climate Predictors, and Global Climate Model

    NASA Astrophysics Data System (ADS)

    Cannon, A. J.

    2006-12-01

    Hydrological models are one of the main tools used to investigate low flows under future climate change scenarios. Climate data requirements range from high-resolution spatially gridded datasets for distributed hydrological models to site measurements for conceptual hydrological models. In either case, climatological information from coarse resolution Global Climate Models (GCMs) must be used to infer climate series at higher resolutions required by the hydrological models. This is typically done using a procedure known as climate downscaling. The effect of the choice of downscaling algorithm, synoptic-scale predictor dataset, and GCM on the sensitivity of low flow simulations by the HBV-EC hydrological model is the main focus of this study. Different statistical downscaling algorithms (an analog model, a non-parametric weather generator, and a conditional density artificial neural network), predictor datasets (drawn from global atmospheric model reanalyses), and GCMs (the Meteorological Service of Canada's CGCM2, the UK Met Office's HadCM3, and the US Department of Energy sponsored PCM) are used to drive the HBV-EC hydrological model in mountainous watersheds of British Columbia, Canada. The ability of the modeling system to reproduce low flows is validated on historical data and simulated low flows are analyzed for future climate change scenarios.

  9. Natural and mining-related sources of dissolved minerals during low flow in the Upper Animas River Basin, southwestern Colorado

    USGS Publications Warehouse

    Wright, Winfield G.

    1997-01-01

    As part of the Clean Water Act of 1972 (Public Law 92-500), all States are required to establish water-quality standards for every river basin in the State. During 1994, the Colorado Department of Public Health and Environment proposed to the Colorado Water Quality Control Commission (CWQCC) an aquatic-life standard of 225 µg/L (micrograms per liter) for the dissolved-zinc concentration in the Animas River downstream from Silverton (fig.1). The CWQCC delayed implementation of this water-quality standard until further information was collected and a plan for the cleanup of abandoned mines was developed. Dissolved-zinc concentrations in this section of the river ranged from about 270 µg/L during high flow, when rainfall and snowmelt runoff dilute the dissolved minerals in the river (U.S. Geological Survey, 1996, p. 431), to 960 µg/L (Colorado Department of Public Health and Environment, written commun., 1996) during low flow (such as late summer and middle winter when natural springs and drainage from mines are the main sources for the streams). Mining sites in the basin were developed between about 1872 and the 1940's, with only a few mines operated until the early 1990's. For local governments, mining sites represent part of the Nation's heritage, tourists are attracted to the historic mining sites, and governments are obligated to protect the historic mining sites according to the National Historic Preservation Act (Public Law 89-665). In the context of this fact sheet, the term "natural sources of dissolved minerals" refers to springs and streams where no effect from mining were determined. "Mining-related sources of dissolved minerals" are assumed to be: (1 ) Water draining from mines , and (2) water seeping from mine-waste dump pile where the waste piles were saturated by water draining from mines. Although rainfall and snowmelt runoff from mine-waste piles might affect water quality in streams, work described in this fact sheet was done during low-flow

  10. Water allocation assessment in low flow river under data scarce conditions: a study of hydrological simulation in Mediterranean basin.

    PubMed

    Bangash, Rubab F; Passuello, Ana; Hammond, Michael; Schuhmacher, Marta

    2012-12-01

    River Francolí is a small river in Catalonia (northeastern Spain) with an average annual low flow (~2 m(3)/s). The purpose of the River Francolí watershed assessments is to support and inform region-wide planning efforts from the perspective of water protection, climate change and water allocation. In this study, a hydrological model of the Francolí River watershed was developed for use as a tool for watershed planning, water resource assessment, and ultimately, water allocation purposes using hydrological data from 2002 to 2006 inclusive. The modeling package selected for this application is DHI's MIKE BASIN. This model is a strategic scale water resource management simulation model, which includes modeling of both land surface and subsurface hydrological processes. Topographic, land use, hydrological, rainfall, and meteorological data were used to develop the model segmentation and input. Due to the unavailability of required catchment runoff data, the NAM rainfall-runoff model was used to calculate runoff of all the sub-watersheds. The results reveal a potential pressure on the availability of groundwater and surface water in the lower part of River Francolí as was expected by the IPCC for Mediterranean river basins. The study also revealed that due to the complex hydrological regime existing in the study area and data scarcity, a comprehensive physically based method was required to better represent the interaction between groundwater and surface water. The combined ArcGIS/MIKE BASIN models appear as a useful tool to assess the hydrological cycle and to better understand water allocation to different sectors in the Francolí River watershed. PMID:22939610

  11. One-layer microfluidic device for hydrodynamic 3D self-flow-focusing operating in low flow speed

    NASA Astrophysics Data System (ADS)

    Daghighi, Yasaman; Gnyawali, Vaskar; Strohm, Eric M.; Tsai, Scott S. H.; Kolios, Michael C.

    2016-03-01

    Hydrodynamic 3D flow-focusing techniques in microfluidics are categorized as (a) sheathless techniques which require high flow rates and long channels, resulting in high operating cost and high flow rates which are inappropriate for applications with flow rate limitations, and (b) sheath-flow based techniques which usually require excessive sheath flow rate to achieve hydrodynamic 3D flow-focusing. Many devices based on these principles use complicated fabrication methods to create multi-layer microchannels. We have developed a sheath-flow based microfluidic device that is capable of hydrodynamic 3D self-flow-focusing. In this device the main flow (black ink) in a low speed, and a sheath flow, enter through two inlets and enter a 180 degree curved channel (300 × 300 μm cross-section). Main flow migrates outwards into the sheath-flow due to centrifugal effects and consequently, vertical focusing is achieved at the end of the curved channel. Then, two other sheath flows horizontally confine the main flow to achieve horizontal focusing. Thus, the core flow is three-dimensionally focused at the center of the channel at the downstream. Using centrifugal force for 3D flow-focusing in a single-layer fabricated microchannel has been previously investigated by few groups. However, their demonstrated designs required high flow speed (>1 m/s) which is not suitable for many applications that live biomedical specie are involved. Here, we introduce a new design which is operational in low flow speed (<0.05 m/s) and is suitable for applications involving live cells. This microfluidic device can be used in detecting, counting and isolating cells in many biomedical applications.

  12. Development and application of generalized-least-squares regression models to estimate low-flow duration discharges in Massachusetts

    USGS Publications Warehouse

    Ries, Kernell G., III

    1994-01-01

    Physically based mathematical models were developed by use of generalized-least-squares regression analyses to estimate long-term 95-, 98-, and 99-percent duration discharges for ungaged streams in Massachusetts. Duration discharges for 61 sites were used in the recession analyses; 37 sites were streamflow-gaging stations and 24 sites were low-flow partial-record stations. The duration discharges were related to basin chacteristics measured from digital data bases, by use of geographic information systems computer software. Significant chacterisfics used in the models were drainage area, area underlain by stratified-drift deposits per unit of stream length in the basin, and a surrogate for the effective head on the aquifer in the stratified-drift deposits, computed by subtracting the minimum basin elevation from the mean basin elevation. Standard errors of prediction were 57.5, 85.6, and 98.5 percent for models for the 95-, 98-, and 99-percent duration discharges, respectively. Model error variances were about 10 times the sampling error variances, indicating that the precision of future models are likely to be improved more by obtaining better measurements of basin characteristics or by adding new sites to the analyses than by collecting more streamflow data at the sites presently used in the analyses. The models were used to predict duration discharges for 35 selected sites in the Concord River, Noah Coastal, South Coastal, Narragansett and Tenmile River Basins. Ninety-perrcent prediction intervals were computed for the estimates at each of the sites, except at sites where values of the independent variables were outside the ranges of those for the sites used in the regression analyses.

  13. Elemental analyses of goundwater: demonstrated advantage of low-flow sampling and trace-metal clean techniques over standard techniques

    NASA Astrophysics Data System (ADS)

    Creasey, C. L.; Flegal, A. R.

    The combined use of both (1) low-flow purging and sampling and (2) trace-metal clean techniques provides more representative measurements of trace-element concentrations in groundwater than results derived with standard techniques. The use of low-flow purging and sampling provides relatively undisturbed groundwater samples that are more representative of in situ conditions, and the use of trace-element clean techniques limits the inadvertent introduction of contaminants during sampling, storage, and analysis. When these techniques are applied, resultant trace-element concentrations are likely to be markedly lower than results based on standard sampling techniques. In a comparison of data derived from contaminated and control groundwater wells at a site in California, USA, trace-element concentrations from this study were 2-1000 times lower than those determined by the conventional techniques used in sampling of the same wells prior to (5months) and subsequent to (1month) the collections for this study. Specifically, the cadmium and chromium concentrations derived using standard sampling techniques exceed the California Maximum Contaminant Levels (MCL), whereas in this investigation concentrations of both of those elements are substantially below their MCLs. Consequently, the combined use of low-flow and trace-metal clean techniques may preclude erroneous reports of trace-element contamination in groundwater. Résumé L'utilisation simultanée de la purge et de l'échantillonnage à faible débit et des techniques sans traces de métaux permet d'obtenir des mesures de concentrations en éléments en traces dans les eaux souterraines plus représentatives que les résultats fournis par les techniques classiques. L'utilisation de la purge et de l'échantillonnage à faible débit donne des échantillons d'eau souterraine relativement peu perturbés qui sont plus représentatifs des conditions in situ, et le recours aux techniques sans éléments en traces limite l

  14. Elemental analyses of goundwater: demonstrated advantage of low-flow sampling and trace-metal clean techniques over standard techniques

    NASA Astrophysics Data System (ADS)

    Creasey, C. L.; Flegal, A. R.

    The combined use of both (1) low-flow purging and sampling and (2) trace-metal clean techniques provides more representative measurements of trace-element concentrations in groundwater than results derived with standard techniques. The use of low-flow purging and sampling provides relatively undisturbed groundwater samples that are more representative of in situ conditions, and the use of trace-element clean techniques limits the inadvertent introduction of contaminants during sampling, storage, and analysis. When these techniques are applied, resultant trace-element concentrations are likely to be markedly lower than results based on standard sampling techniques. In a comparison of data derived from contaminated and control groundwater wells at a site in California, USA, trace-element concentrations from this study were 2-1000 times lower than those determined by the conventional techniques used in sampling of the same wells prior to (5months) and subsequent to (1month) the collections for this study. Specifically, the cadmium and chromium concentrations derived using standard sampling techniques exceed the California Maximum Contaminant Levels (MCL), whereas in this investigation concentrations of both of those elements are substantially below their MCLs. Consequently, the combined use of low-flow and trace-metal clean techniques may preclude erroneous reports of trace-element contamination in groundwater. Résumé L'utilisation simultanée de la purge et de l'échantillonnage à faible débit et des techniques sans traces de métaux permet d'obtenir des mesures de concentrations en éléments en traces dans les eaux souterraines plus représentatives que les résultats fournis par les techniques classiques. L'utilisation de la purge et de l'échantillonnage à faible débit donne des échantillons d'eau souterraine relativement peu perturbés qui sont plus représentatifs des conditions in situ, et le recours aux techniques sans éléments en traces limite l

  15. Ulinastatin Protects against Acute Kidney Injury in Infant Piglets Model Undergoing Surgery on Hypothermic Low-Flow Cardiopulmonary Bypass

    PubMed Central

    Wang, Xiaocou; Xue, Qinghua; Yan, Fuxia; Liu, Jinping; Li, Shoujun; Hu, Shengshou

    2015-01-01

    Objective Infants are more vulnerable to kidney injuries induced by inflammatory response syndrome and ischemia-reperfusion injury following cardiopulmonary bypass especially with prolonged hypothermic low-flow (HLF). This study aims to evaluate the protective role of ulinastatin, an anti-inflammatory agent, against acute kidney injuries in infant piglets model undergoing surgery on HLF cardiopulmonary bypass. Methods Eighteen general-type infant piglets were randomly separated into the ulinastatin group (Group U, n = 6), the control group (Group C, n = 6), and the sham operation group (Group S, n = 6), and anaesthetized. The groups U and C received following experimental procedure: median thoracotomy, routine CPB and HLF, and finally weaned from CPB. The group S only underwent sham median thoracotomy. Ulinastatin at a dose of 5,000 units/kg body weight and a certain volume of saline were administrated to animals of the groups U and C at the beginning of CPB and at aortic declamping, respectively. Venous blood samples were collected at 3 different time points: after anesthesia induction in all experimental groups, 5 minutes, and 120 minutes after CPB in the Groups U and C. Markers for inflammation and acute kidney injury were tested in the collected plasma. N-acetyl-β-D-glucosaminidase (NAG) from urine, markers of oxidative stress injury and TUNEL-positive cells in kidney tissues were also detected. Results The expressions of plasma inflammatory markers and acute kidney injury markers increased both in Group U and Group C at 5 min and 120 min after CPB. Also, numbers of TUNEL-positive cells and oxidative stress markers in kidney rose in both groups. At the time point of 120-min after CPB, compared with the Group C, some plasma inflammatory and acute kidney injury markers as well as TUNEL-positive cells and oxidative stress markers in kidney were significantly reduced in the Group U. Histologic analyses showed that HLF promoted acute tubular necrosis and dilatation

  16. Ultra-low Flow Liquid Chromatography Assay with Ultraviolet (UV) Detection for Piperine Quantitation in Human Plasma

    PubMed Central

    Kakarala, Madhuri; Dubey, Shiv Kumar; Tarnowski, Malloree; Cheng, Connie; Liyanage, Samadhi; Strawder, Terrence; Tazi, Karim; Sen, Ananda; Djuric, Zora; Brenner, Dean E.

    2015-01-01

    A robust and sensitive ultra-low flow liquid chromatography (UFLC) method that can reproducibly, at reasonable cost, detect low concentrations of piperine from human plasma is necessary. Piperine in plasma was separated and quantified by a gradient method using ultraviolet detection at a maximal absorbance wavelength of 340 nm. An aliquot was injected onto a reversed-phase column Waters SymmetryShield, 2.1 × 100 mm, 3.5 μm, C18 column, attached to a Waters absorbosphere, 4.6 × 30 mm, C18 guard column and eluted with a mobile phase containing a mixture of acetonitrile/water/ acetic acid (25:74.9:0.1, v/v/v) on line A and acetonitrile/acetic acid (99.9:0.1, v/v) on line B. The flow rate was 0.3 mL/min. The gradient method consisted of an opening condition of 20% pump B, with a linear increase to 37% pump B over 8 min, then a linear increase to 100% pump B at 11 min, 2 min at 100% pump B, and then a return to the opening condition (20% pump B) via a linear gradient over 2 min, followed by 5 min re-equilibration at opening conditions. The total run time was 20 min for each sample. All samples were processed protected from ambient light to avoid isomerization of piperine. The plasma assay was linear with R = 0.9995, with a lower limit of detection [signal-to-noise (S/N) > 5:1] of 100 pg of piperine loaded into the analytical system with acceptable accuracy and precision. Extraction recoveries of piperine from human plasma were 88% for quality control high (QCH), 93% for quality control medium (QCM), and 90% for quality control low (QCL), and the matrix effect was <12%. Piperine was quantifiable from a 50 mg oral dose given to human volunteers. A UFLC method for the rapid assay of human plasma with sensitivity to detect as low as 5 ng/mL piperine was developed. The method sensitivity equals that of liquid chromatography/tandem mass spectrometry (LC/MSMS) methods with much less cost. PMID:20465211

  17. Statistical summaries of streamflow records, Oklahoma through 1974: compilations of flow-duration, low-flow, high-flow, monthly duration tables and statistics of annual discharge through 1974

    USGS Publications Warehouse

    Mize, Lionel D.

    1975-01-01

    Tables summarizing daily streamflow data by year are presented for gaging stations in Oklahoma that have at least 5 years of either unregulated or regulated stream-gaging record through September 30, 1974. Separate tables are presented for unregulated and regulated periods of record. These summary tables include: (1) the number of days in each year that the daily discharge was between selected limits (duration tables), (2) the lowest mean daily discharge (frequency tables), (3) the highest mean daily discharge (frequency tables), (4) a monthly duration table for each station with 29 years or more of essentially unregulated record, and (5) statistics of annual discharge. These summaries provide useful information about the quantity, distribution, and variability of streamflow and provide basic data for developing relations for estimating streamflow at sites other than regular stream-gaging sites. This information is also useful in designing bridges, culverts, and other hydraulic structures as well as reservoirs for water supply, flood control, and low-flow regulation.

  18. Frequency Combs

    NASA Astrophysics Data System (ADS)

    Hänsch, Theodor W.; Picqué, Nathalie

    Much of modern research in the field of atomic, molecular, and optical science relies on lasers, which were invented some 50 years ago and perfected in five decades of intense research and development. Today, lasers and photonic technologies impact most fields of science and they have become indispensible in our daily lives. Laser frequency combs were conceived a decade ago as tools for the precision spectroscopy of atomic hydrogen. Through the development of optical frequency comb techniques, technique a setup of the size 1 ×1 m2, good for precision measurements of any frequency, and even commercially available, has replaced the elaborate previous frequency-chain schemes for optical frequency measurements, which only worked for selected frequencies. A true revolution in optical frequency measurements has occurred, paving the way for the creation of all-optical clocks clock with a precision that might approach 10-18. A decade later, frequency combs are now common equipment in all frequency metrology-oriented laboratories. They are also becoming enabling tools for an increasing number of applications, from the calibration of astronomical spectrographs to molecular spectroscopy. This chapter first describes the principle of an optical frequency comb synthesizer. Some of the key technologies to generate such a frequency comb are then presented. Finally, a non-exhaustive overview of the growing applications is given.

  19. Postoperative Low-Flow Cerebrospinal Fluid Leak of Endoscopic Endonasal Transsphenoidal Surgery for Pituitary Adenoma--Wait and See, or Lumbar Drain?

    PubMed

    Zhan, Rucai; Chen, Songyu; Xu, Shujun; Liu, James K; Li, Xingang

    2015-06-01

    To assess the effectiveness of continuous lumbar drainage (LD) for management of postoperative cerebrospinal fluid leaks after endoscopic endonasal transsphenoidal approach for resection of pituitary adenoma. Three hundred eighty-four medical records of patients who were admitted to our institute during a 2.5-year period were retrospectively reviewed, 33 of them experienced low-flow cerebrospinal fluid leak postoperatively. If LD was used, all patients with low-flow cerebrospinal fluid leak were classified into 2 groups, lumbar drained group and conservatively treated group. The age, sex, management of cerebrospinal fluid leaks, and related complications were reviewed. Statistical comparisons between the 2 groups were made using SPSS 19.0 (IBM Corp, Armonk, NY). The differences were considered statistically significant if the P value was less than 0.05.Thirty-three of 384 (8.6%) experienced low-flow postoperative cerebrospinal fluid leaks. Cured rate of cerebrospinal fluid leak was 94.4% (17/18) in continuous lumbar drained group, and 93.3% (14/15) in control group. There were 2 (11.2%) patients who developed meningitis in the LD group and 1 (5.6%) patient in the control group. One patient required endoscopic repair of skull base because of persistent cerebrospinal fluid leak in both groups, with the rates of 5.6% and 6.7%, respectively. There was no significant difference noted in each rate in both groups.Placement of LD may not be necessary for the management of low-flow postoperative cerebrospinal fluid leak after using endoscopic endonasal transsphenoidal approach to pituitary adenoma. PMID:26080170

  20. Sensitivity analysis of non-point sources in a water quality model applied to a dammed low-flow-reach river.

    PubMed

    Silva, Nayana G M; von Sperling, Marcos

    2008-01-01

    Downstream of Capim Branco I hydroelectric dam (Minas Gerais state, Brazil), there is the need of keeping a minimum flow of 7 m3/s. This low flow reach (LFR) has a length of 9 km. In order to raise the water level in the low flow reach, the construction of intermediate dikes along the river bed was decided. The LFR has a tributary that receives the discharge of treated wastewater. As part of this study, water quality of the low-flow reach was modelled, in order to gain insight into its possible behaviour under different scenarios (without and with intermediate dikes). QUAL2E equations were implemented in FORTRAN code. The model takes into account point-source pollution and diffuse pollution. Uncertainty analysis was performed, presenting probabilistic results and allowing identification of the more important coefficients in the LFR water-quality model. The simulated results indicate, in general, very good conditions for most of the water quality parameters The variables of more influence found in the sensitivity analysis were the conversion coefficients (without and with dikes), the initial conditions in the reach (without dikes), the non-point incremental contributions (without dikes) and the hydraulic characteristics of the reach (with dikes). PMID:18469404

  1. Independent technical review and analysis of hydraulic modeling and hydrology under low-flow conditions of the Des Plaines River near Riverside, Illinois

    USGS Publications Warehouse

    Over, Thomas M.; Straub, Timothy D.; Hortness, Jon E.; Murphy, Elizabeth A.

    2012-01-01

    The U.S. Geological Survey (USGS) has operated a streamgage and published daily flows for the Des Plaines River at Riverside since Oct. 1, 1943. A HEC-RAS model has been developed to estimate the effect of the removal of Hofmann Dam near the gage on low-flow elevations in the reach approximately 3 miles upstream from the dam. The Village of Riverside, the Illinois Department of Natural Resources-Office of Water Resources (IDNR-OWR), and the U. S. Army Corps of Engineers-Chicago District (USACE-Chicago) are interested in verifying the performance of the HEC-RAS model for specific low-flow conditions, and obtaining an estimate of selected daily flow quantiles and other low-flow statistics for a selected period of record that best represents current hydrologic conditions. Because the USGS publishes streamflow records for the Des Plaines River system and provides unbiased analyses of flows and stream hydraulic characteristics, the USGS served as an Independent Technical Reviewer (ITR) for this study.

  2. The acute effects of low flow oxygen and isosorbide dinitrate on left and right ventricular ejection fractions in chronic obstructive pulmonary disease

    SciTech Connect

    Morrison, D.; Caldwell, J.; Lakshminaryan, S.; Ritchie, J.L.; Kennedy, J.W.

    1983-10-01

    The objectives of this study were to determine the effects of low flow oxygen and isosorbide dinitrate on rest and exercise biventricular ejection fractions in patients with chronic obstructive pulmonary disease and to relate these ejection fraction responses to changes in pressure and flow. Nine patients with stable, moderate to severe chronic obstructive pulmonary disease who had no prior history of heart failure performed supine exercise with simultaneous hemodynamic and radionuclide ventriculographic monitoring. Eight patients performed a second exercise during low flow oxygen breathing and five performed a third exercise after ingesting 10 mg oral isosorbide. Oxygen led to a decrease in exercise pulmonary artery pressure in all subjects and a decline in total pulmonary resistance in five of the seven in whom it was measured. Right ventricular ejection fraction increased 0.05 or more only in subjects who had a decrease in total pulmonary resistance. Isosorbide led to an increase in rest and exercise right and left ventricular ejection fractions with simultaneous decreases in pulmonary artery pressure, total pulmonary resistance, blood pressure and arterial oxygen tension. These results suggest that in patients with chronic obstructive pulmonary disease but without a history of right heart failure, the right ventricular systolic functional response to low flow oxygen and isosorbide at rest and exercise is, in part, determined by changes in total pulmonary resistance. The chronic relation between right ventricular ejection fraction and pulmonary hemodynamics in patients with chronic obstructive pulmonary disease remains to be evaluated.

  3. WATER-QUALITY CONDITIONS DURING LOW FLOW IN THE LOWER YOUGHIOGHENY RIVER BASIN, PENNSYLVANIA, OCTOBER 5-7, 1998

    SciTech Connect

    James I. Sams, III, Karl T. Schroeder; Terry E. Ackman; J. Kent Crawford; Kim L. Otto

    2001-01-01

    In October 1998, a chemical synoptic survey was conducted by the U.S. Geological Survey, in cooperation with the U.S. Department of Energy, National Energy Technology Laboratory, in the Lower Youghiogheny River Basin in Pennsylvania to give a snap-shot of present (1998) water quality during low-flow conditions. Water samples from 38 sites--12 mainstem sites, 22 tributaries, and 4 mine discharges that discharge directly to the Youghiogheny River--were used to identify sources of contaminants from mining operations. Specific conductance, water temperature, pH, and dissolved oxygen were measured in the field at each site and concentrations of major ions and trace elements were measured in the laboratory. Unaccounted for gains and losses in streamflow were measured during the study. Unaccounted for losses in streamflow might be attributed to water loss through streambed fractures. Extensive mine tunnels are present in the basin and loss of water to these tunnels seems likely. Unaccounted for gains in streamflow may be from unmeasured tributaries or surface seeps, but most of the gains are suspected to come from artesian flow through fractures in the streambed from underground mine pools. Influent flows of rust-colored water were noted in some river sections. The pH values for all the samples collected during this survey were above 5.8, and most (33 of 38 samples) were above 7.0. Samples from the four mine-discharge sites also had pH values between 6.3 and 6.7. The lowest pH (5.8) was in a tributary, Galley Run. All 38 sampling sites had net alkalinity. The alkalinity load in the Youghiogheny River increased between Connellsville and McKeesport from 35 to 79 tons per day. Above Smithton, the measured alkalinity load in the Lower Youghiogheny River agreed well with the estimated alkalinity load. Below Smithton, measured alkalinity loads in the Lower Youghiogheny River are greater than calculated loads, resulting in unaccounted for gains in alkalinity. These gains are

  4. Review Of Low-Flow Bladder Pump And High-Volume Air Piston Pump Groundwater Sampling Systems At Sandia National Laboratories, New Mexico

    SciTech Connect

    Collins, S. S.; Bailey, G. A.; Jackson, T. O.

    2003-02-25

    Since 1996, Sandia National Laboratories, New Mexico (SNL/NM) has run both a portable high-volume air-piston pump system and a dedicated, low-flow bladder pump system to collect groundwater samples. The groundwater contaminants of concern at SNL/NM are nitrate and the volatile organic compounds trichloroethylene (TCE) and tetrachloethene (PCE). Regulatory acceptance is more common for the high-volume air piston pump system, especially for programs like SNL/NM's, which are regulated under the Resource Conservation and Recovery Act (RCRA). This paper describes logistical and analytical results of the groundwater sampling systems used at SNL/NM. With two modifications to the off-the-shelf low-flow bladder pump, SNL/NM consistently operates the dedicated low-flow system at depths greater than 450 feet below ground surface. As such, the low-flow sampling system requires fewer personnel, less time and materials, and generates less purge and decontamination water than does the high-volume system. However, the bladder pump cannot work in wells with less than 4 feet of water. A review of turbidity and laboratory analytical results for TCE, PCE, and chromium (Cr) from six wells highlight the affect or lack of affects the sampling systems have on groundwater samples. In the PVC wells, turbidity typically remained < 5 nephelometric turbidity units (NTU) regardless of the sampling system. In the wells with a stainless steel screen, turbidity typically remained < 5 NTU only with the low-flow system. When the high-volume system was used, the turbidity and Cr concentration typically increased an order of magnitude. TCE concentrations at two wells did not appear to be sensitive to the sampling method used. However, PCE and TCE concentrations dropped an order of magnitude when the high-volume system was used at two other wells. This paper recommends that SNL/NM collaborate with other facilities with similar groundwater depths, continue to pursue regulatory approval for using

  5. Estimation of selected streamflow statistics for a network of low-flow partial-record stations in areas affected by Base Realignment and Closure (BRAC) in Maryland

    USGS Publications Warehouse

    Ries, Kernell G., III; Eng, Ken

    2010-01-01

    The U.S. Geological Survey, in cooperation with the Maryland Department of the Environment, operated a network of 20 low-flow partial-record stations during 2008 in a region that extends from southwest of Baltimore to the northeastern corner of Maryland to obtain estimates of selected streamflow statistics at the station locations. The study area is expected to face a substantial influx of new residents and businesses as a result of military and civilian personnel transfers associated with the Federal Base Realignment and Closure Act of 2005. The estimated streamflow statistics, which include monthly 85-percent duration flows, the 10-year recurrence-interval minimum base flow, and the 7-day, 10-year low flow, are needed to provide a better understanding of the availability of water resources in the area to be affected by base-realignment activities. Streamflow measurements collected for this study at the low-flow partial-record stations and measurements collected previously for 8 of the 20 stations were related to concurrent daily flows at nearby index streamgages to estimate the streamflow statistics. Three methods were used to estimate the streamflow statistics and two methods were used to select the index streamgages. Of the three methods used to estimate the streamflow statistics, two of them--the Moments and MOVE1 methods--rely on correlating the streamflow measurements at the low-flow partial-record stations with concurrent streamflows at nearby, hydrologically similar index streamgages to determine the estimates. These methods, recommended for use by the U.S. Geological Survey, generally require about 10 streamflow measurements at the low-flow partial-record station. The third method transfers the streamflow statistics from the index streamgage to the partial-record station based on the average of the ratios of the measured streamflows at the partial-record station to the concurrent streamflows at the index streamgage. This method can be used with as few as

  6. Which landscape elements support streamflow during low flow conditions? Lessons from field observations in the Swiss midlands in dry summer 2015

    NASA Astrophysics Data System (ADS)

    Floriancic, Marius; Margreth, Michael; Naef, Felix

    2016-04-01

    Low flows can be very heterogeneous even on small scale. It is not well known which areas contribute to low flow during extended dry periods nor can we expect which challenges will arise with changing climate conditions. Therefore we need to improve our understanding of physical properties relevant for water storage and drainage during dry periods. We present a spatially resolved discharge dataset from the Swiss midlands during the extended dry summer 2015. On very small scales we found major differences in discharge: neighboring nested subcatchments varied by up to a factor of 5. These variations correspond to certain landscape elements. Required storage volumes are quite small, making up only about 1% of annual precipitation, but some features are more likely to support higher streamflow during dry periods due to slow drainage. We found significant evidence for differences in storage and drainage behavior, existence of sections of streambed infiltration and point sources of outstanding contribution along the stream networks of the Swiss midlands and Alps. Major differences can be traced back to different lithology, slope angles and connectivity of storage features to the network. Even though heterogeneity is high on small scale, spatial scale of the research is limited by point source contribution, subsurface flow paths and streambed infiltration and exfiltration. These findings show the significant extent to which different geological formations with certain physical properties contribute to low flow discharge in midland environments. Understanding the effects of physical landscape properties is a first step to get an insight of water storage capacity and the relevant drainage timescale supporting streamflow during extended dry periods. This helps to find areas that are either sensitive or resistant to changes towards a dryer climate.

  7. Testing the hydrological landscape unit classification system and other terrain analysis measures for predicting low-flow nitrate and chloride in watersheds.

    PubMed

    Poor, Cara J; McDonnell, Jeffrey J; Bolte, John

    2008-11-01

    Elevated nitrate concentrations in streamwater are a major environmental management problem. While land use exerts a large control on stream nitrate, hydrology often plays an equally important role. To date, predictions of low-flow nitrate in ungauged watersheds have been poor because of the difficulty in describing the uniqueness of watershed hydrology over large areas. Clearly, hydrologic response varies depending on the states and stocks of water, flow pathways, and residence times. How to capture the dominant hydrological controls that combine with land use to define streamwater nitrate concentration is a major research challenge. This paper tests the new Hydrologic Landscape Regions (HLRs) watershed classification scheme of Wolock and others (Environmental Management 34:S71-S88, 2004) to address the question: Can HLRs be used as a way to predict low-flow nitrate? We also test a number of other indexes including inverse-distance weighting of land use and the well-known topographic index (TI) to address the question: How do other terrain and land use measures compare to HLR in terms of their ability to predict low-flow nitrate concentration? We test this for 76 watersheds in western Oregon using the U.S. Environmental Protection Agency's Environmental Monitoring and Assessment Program and Regional Environmental Monitoring and Assessment Program data. We found that HLRs did not significantly improve nitrate predictions beyond the standard TI and land-use metrics. Using TI and inverse-distance weighting did not improve nitrate predictions; the best models were the percentage land use-elevation models. We did, however, see an improvement of chloride predictions using HLRs, TI, and inverse-distance weighting; adding HLRs and TI significantly improved model predictions and the best models used inverse-distance weighting and elevation. One interesting result of this study is elevation consistently predicted nitrate better than TI or the hydrologic classification

  8. Assessment of chlorophyll-a variations in high- and low-flow seasons in Apalachicola Bay by MODIS 250-m remote sensing.

    PubMed

    Huang, Wenrui; Chen, Shuisen; Yang, Xiaojun; Johnson, Elijah

    2014-12-01

    Chlorophyll-a (chl-a) is considered as a primary indicator for water quality and foods for oyster growth in Apalachicola estuarine ecosystem. Assessment of chl-a concentration variation in response to river inflow is important for estuarine environmental research and management. In this study, remote sensing analysis has been conducted to evaluate the effects of river inflow on chlorophyll concentrations in Apalachicola Bay of Florida in the northeast Gulf of Mexico. A remote sensing model for chl-a was improved and applied to map spatial distributions of chl-a by using Moderate Resolution Imaging Spectroradiometer (MODIS) 250-m resolution imageries in high-flow and low-flow seasons in 2001 and 2008. Chl-a values approximately ranged from the minimum 6 μg/l to the maximum 29 μg/l in the study period. Maximum chl-a concentration in high-flow season was almost twice above that in low-flow season. The averaged mean and minimum chl-a level in the high-flow season were approximately 42 and 28 % higher than those in low-flow season, respectively. The remote sensing mapping of chl-a was able to show spatial variations of chl-a in the entire bay under different flow conditions, which indicated its advantage over the traditional field data sampling for monitoring water quality over a large area of estuary. The MODIS 250-m remote sensing regression model presented from this study can be used to support monitoring and assessment of the spatial chl-a distribution in the bay for environmental research and management in Apalachicola Bay. PMID:25213560

  9. Frequency spirals

    NASA Astrophysics Data System (ADS)

    Ottino-Löffler, Bertrand; Strogatz, Steven H.

    2016-09-01

    We study the dynamics of coupled phase oscillators on a two-dimensional Kuramoto lattice with periodic boundary conditions. For coupling strengths just below the transition to global phase-locking, we find localized spatiotemporal patterns that we call "frequency spirals." These patterns cannot be seen under time averaging; they become visible only when we examine the spatial variation of the oscillators' instantaneous frequencies, where they manifest themselves as two-armed rotating spirals. In the more familiar phase representation, they appear as wobbly periodic patterns surrounding a phase vortex. Unlike the stationary phase vortices seen in magnetic spin systems, or the rotating spiral waves seen in reaction-diffusion systems, frequency spirals librate: the phases of the oscillators surrounding the central vortex move forward and then backward, executing a periodic motion with zero winding number. We construct the simplest frequency spiral and characterize its properties using analytical and numerical methods. Simulations show that frequency spirals in large lattices behave much like this simple prototype.

  10. Intractable Posterior Epistaxis due to a Spontaneous Low-Flow Carotid-Cavernous Sinus Fistula: A Case Report and a Review of the Literature

    PubMed Central

    Giotakis, A.; Kral, F.; Riechelmann, H.; Freund, M.

    2015-01-01

    We report a case of a 90-year-old patient with intractable posterior epistaxis presenting as the only symptom of a nontraumatic low-flow carotid-cavernous sinus fistula. Purpose of this case report is to introduce low-flow carotid-cavernous sinus fistula in the differential diagnosis of intractable posterior epistaxis. We provide a literature review for the sequence of actions for the confrontation of posterior epistaxis. We also emphasize the significance of the radiological diagnostic and therapeutic procedures in the management of posterior epistaxis due to pathology of the cavernous sinus. The gold-standard diagnostic procedure of carotid-cavernous sinus fistula is digital subtraction angiography (DSA). DSA with coils is also the state-of-the-art therapy. By failure of DSA, neurosurgery or stereotactic radiosurgery (SRS) may be used as alternatives. SRS may also be used as enhancement procedure of the DSA. Considering the prognosis of a successfully closed carotid-cavernous sinus fistula, recanalization occurs only in a minority of patients. Close follow-up is advised. PMID:26839726

  11. Effects of basin size on low-flow stream chemistry and subsurface contact time in the neversink river watershed, New York

    USGS Publications Warehouse

    Wolock, D.M.; Fan, J.; Lawrence, G.B.

    1997-01-01

    The effects of basin size on low-flow stream chemistry and subsurface contact time were examined for a part of the Neversink River watershed in southern New York State. Acid neutralizing capacity (ANC), the sum of base cation concentrations (SBC), pH and concentrations of total aluminum (Al), dissolved organic carbon (DOC) and silicon (Si) were measured during low stream flow at the outlets of nested basins ranging in size from 0.2 to 166.3 km2. ANC, SBC, pH, Al and DOC showed pronounced changes as basin size increased from 0.2 to 3 km2, but relatively small variations were observed as basin size increased beyond 3 km2. An index of subsurface contact time computed from basin topography and soil hydraulic conductivity also showed pronounced changes as basin size increased from 0.2 to 3 km2 and smaller changes as basin size increased beyond 3 km2. These results suggest that basin size affects low-flow stream chemistry because of the effects of basin size on subsurface contact time. ?? 1997 by John Wiley & Sons, Ltd.

  12. Laminated metal composite formed from low flow stress layers and high flow stress layers using flow constraining elements and method of making same

    SciTech Connect

    Syn, C.K.; Lesuer, D.R.

    1994-12-31

    This invention relates to a laminated metal composite, comprising alternating layers of low flow stress material and high flow stress material, and formed using flow constraining elements around each low flow stress layer; and a method of making same. A composite is a combination of at least two chemically distinct materials with a distinct interface separating the two materials. A metal matrix composite (MMC) is a composite material composed of a metal and a nonmetallic reinforcing agent such as silicon carbide (SiC) or graphite in continuous or discontinuous fiber, whisker, or discrete particulate form. A laminate is a material composed of several bonded layers. It is possible to have a laminate composed of multi-layers of a single type of material bonded to each other. However, such a laminate would not be considered to be a composite. The term {open_quotes}laminated metal composite{close_quotes} (LMC), as used herein, is intended to include a structural material composed of: (1) layers of metal or metal alloys interleaved with (2) a different metal, a metal alloy, or a metal matrix composite (MMC) containing strengthening agents.

  13. Occurrence of dissolved solids, nutrients, atrazine, and fecal coliform bacteria during low flow in the Cheney Reservoir watershed, south-central Kansas, 1996

    USGS Publications Warehouse

    Christensen, V.G.; Pope, L.M.

    1997-01-01

    A network of 34 stream sampling sites was established in the 1,005-square-mile Cheney Reservoir watershed, south-central Kansas, to evaluate spatial variability in concentrations of selected water-quality constituents during low flow. Land use in the Cheney Reservoir watershed is almost entirely agricultural, consisting of pasture and cropland. Cheney Reservoir provides 40 to 60 percent of the water needs for the city of Wichita, Kansas. Sampling sites were selected to determine the relative contribution of point and nonpoint sources of water-quality constituents to streams in the watershed and to identify areas of potential water-quality concern. Water-quality constituents of interest included dissolved solids and major ions, nitrogen and phosphorus nutrients, atrazine, and fecal coliform bacteria. Water from the 34 sampling sites was sampled once in June and once in September 1996 during Phase I of a two-phase study to evaluate water-quality constituent concentrations and loading characteristics in selected subbasins within the watershed and into and out of Cheney Reservoir. Information summarized in this report pertains to Phase I and was used in the selection of six long-term monitoring sites for Phase II of the study. The average low-flow constituent concentrations in water collected during Phase I from all sampling sites was 671 milligrams per liter for dissolved solids, 0.09 milligram per liter for dissolved ammonia as nitrogen, 0.85 milligram per liter for dissolved nitrite plus nitrate as nitrogen, 0.19 milligram per liter for total phosphorus, 0.20 microgram per liter for dissolved atrazine, and 543 colonies per 100 milliliters of water for fecal coliform bacteria. Generally, these constituents were of nonpoint-source origin and, with the exception of dissolved solids, probably were related to agricultural activities. Dissolved solids probably occur naturally as the result of the dissolution of rocks and ancient marine sediments containing large salt

  14. Disturbance frequency influences patch dynamics in stream benthic algal communities.

    PubMed

    Ledger, Mark E; Harris, Rebecca M L; Armitage, Patrick D; Milner, Alexander M

    2008-04-01

    Disturbance is integral to the organisation of riverine ecosystems. Fluctuating low flows caused by supra-seasonal drought and water management periodically dewater habitat patches, potentially creating heterogeneity in the taxonomic composition and successional dynamics of benthic communities. The frequency of disturbance induced by low flows is contingent upon the topography of the river bed and thus varies among patches. We investigated whether the frequency of patch dewatering influenced the structure and temporal dynamics of benthic algal communities attached to the upper surfaces of stones in stream mesocosms (4 m2). In a 693-day disturbance experiment, we applied short dewatering disturbances (6 days) at high (33-day cycles) and low frequencies (99-day cycles) and compared algal assemblages with undisturbed controls at 21 endpoints. In the absence of disturbance, epilithic space was dominated by the green encrusting alga Gongrosira incrustans. However, drying disturbances consistently reduced the dominance of the green alga, and crust abundance decreased with increasing disturbance frequency, thereby opening space for a diversity of mat-forming diatoms. The response of mat diatoms to disturbance varied markedly during the experiment, from strong reductions in the abundance of loosely attached mats in mid-late 2000 to the exploitation of open space by closely adhering mats in 2001. Contrary responses were attributed to changes in the species composition of mat diatoms, which influenced the physiognomy and hence stress-resistance and resilience of the assemblage. Our results indicate that patchy dewatering of habitat patches during periods of low flow influences the successional dynamics of algae, thereby creating distinctive mosaics on the stream bed. PMID:18193289

  15. Physical habitat classification and instream flow modeling to determine habitat availability during low-flow periods, North Fork Shenandoah River, Virginia

    USGS Publications Warehouse

    Krstolic, Jennifer L.; Hayes, Donald C.; Ruhl, Peter M.

    2006-01-01

    Increasing development and increasing water withdrawals for public, industrial, and agricultural water supply threaten to reduce streamflows in the Shenandoah River basin in Virginia. Water managers need more information to balance human water-supply needs with the daily streamflows necessary for maintaining the aquatic ecosystems. To meet the need for comprehensive information on hydrology, water supply, and instream-flow requirements of the Shenandoah River basin, the U.S. Geological Survey and the Northern Shenandoah Valley Regional Commission conducted a cooperative investigation of habitat availability during low-flow periods on the North Fork Shenandoah River. Historic streamflow data and empirical data on physical habitat, river hydraulics, fish community structure, and recreation were used to develop a physical habitat simulation model. Hydraulic measurements were made during low, medium, and high flows in six reaches at a total of 36 transects that included riffles, runs, and pools, and that had a variety of substrates and cover types. Habitat suitability criteria for fish were developed from detailed fish-community sampling and microhabitat observations. Fish were grouped into four guilds of species and life stages with similar habitat requirements. Simulated habitat was considered in the context of seasonal flow regimes to show the availability of flows that sustain suitable habitat during months when precipitation and streamflow are scarce. The North Fork Shenandoah River basin was divided into three management sections for analysis purposes: the upper section, middle section, and lower section. The months of July, August, and September were chosen to represent a low-flow period in the basin with low mean monthly flows, low precipitation, high temperatures, and high water withdrawals. Exceedance flows calculated from the combined data from these three months describe low-flow periods on the North Fork Shenandoah River. Long-term records from three

  16. Heavy and moderate interval exercise training alters low-flow-mediated constriction but does not increase circulating progenitor cells in healthy humans.

    PubMed

    Rakobowchuk, Mark; Harris, Emma; Taylor, Annabelle; Baliga, Vivek; Cubbon, Richard M; Rossiter, Harry B; Birch, Karen M

    2012-03-01

    Moderate-intensity endurance exercise training improves vascular endothelial vasomotor function; however, the impact of high-intensity exercise training has been equivocal. Thus, the effect of the physiological stress of the exercise remains poorly understood. Furthermore, enhanced vascular repair mediated by circulating progenitor cells may also be improved. To address whether the physiological stress of exercise training is an important factor contributing to these adaptations, 20 healthy participants trained for 6 weeks. Training involved either moderate (MSIT; n = 9) or heavy metabolic stress (HSIT; n = 11) interval exercise training programmes matched for total work and duration of exercise. Before and after training, flow-mediated dilatation, low-flow-mediated constriction and total vessel reactivity were measured at the brachial artery using Doppler ultrasound. Circulating progenitor cells (CD34(+), CD133(+) and CD309/KDR(+)) were measured by flow cytometry (means ± SD). Relative (MSIT pre- 5.5 ± 3.4 versus post-training 6.6 ± 2.5%; HSIT pre- 6.6 ± 4.1 versus post-training 7.0 ± 3.4%, P = 0.33) and normalized (P = 0.16) flow-mediated dilatation did not increase with either training programme. However, low-flow-mediated constriction was greater after training in both groups (MSIT pre- -0.5 ± 3.2 versus post-training -1.9 ± 3.1%; HSIT pre- -1.0 ± 1.7 versus post-training -2.9 ± 3.0%, P = 0.04) and contributed to greater total vessel reactivity (MSIT pre- 7.4 ± 3.3 versus post-training 10.1 ± 3.7%; HSIT pre- 10.9 ± 5.9 versus post-training 12.7 ± 6.2%, P = 0.01). Peak reactive hyperaemia and the area under the shear rate curve were not different between groups, either before or after training. Although circulating progenitor cell numbers increased following heavy-intensity interval exercise training, variability was great amongst participants [MSIT pre- 16 ± 18 versus post-training 14 ± 12 cells (ml whole blood)(-1); HSIT pre- 8 ± 6 versus post

  17. Impacts of climate change and socio-economic scenarios on flow and water quality of the Ganges, Brahmaputra and Meghna (GBM) river systems: low flow and flood statistics.

    PubMed

    Whitehead, P G; Barbour, E; Futter, M N; Sarkar, S; Rodda, H; Caesar, J; Butterfield, D; Jin, L; Sinha, R; Nicholls, R; Salehin, M

    2015-06-01

    The potential impacts of climate change and socio-economic change on flow and water quality in rivers worldwide is a key area of interest. The Ganges-Brahmaputra-Meghna (GBM) is one of the largest river basins in the world serving a population of over 650 million, and is of vital concern to India and Bangladesh as it provides fresh water for people, agriculture, industry, conservation and for the delta system downstream. This paper seeks to assess future changes in flow and water quality utilising a modelling approach as a means of assessment in a very complex system. The INCA-N model has been applied to the Ganges, Brahmaputra and Meghna river systems to simulate flow and water quality along the rivers under a range of future climate conditions. Three model realisations of the Met Office Hadley Centre global and regional climate models were selected from 17 perturbed model runs to evaluate a range of potential futures in climate. In addition, the models have also been evaluated using socio-economic scenarios, comprising (1) a business as usual future, (2) a more sustainable future, and (3) a less sustainable future. Model results for the 2050s and the 2090s indicate a significant increase in monsoon flows under the future climates, with enhanced flood potential. Low flows are predicted to fall with extended drought periods, which could have impacts on water and sediment supply, irrigated agriculture and saline intrusion. In contrast, the socio-economic changes had relatively little impact on flows, except under the low flow regimes where increased irrigation could further reduce water availability. However, should large scale water transfers upstream of Bangladesh be constructed, these have the potential to reduce flows and divert water away from the delta region depending on the volume and timing of the transfers. This could have significant implications for the delta in terms of saline intrusion, water supply, agriculture and maintaining crucial ecosystems such

  18. Status of fish communities in the Rio Grande, Big Bend National Park, Texas - comparison before and after Spring 2003 period of low flow

    USGS Publications Warehouse

    Moring, J. Bruce

    2005-01-01

    During 2003–04 the U.S. Geological Survey, in cooperation with the National Park Service, re-evaluated the status of fish communities in three reaches of the Rio Grande in Big Bend National Park that originally were evaluated when the three reaches were established for study in 1999. The objective was to determine whether there were measurable differences between 1999 and 2003–04 (referred to as 2004) fish community status that likely are attributable to a rare 58-day period of low flow (less than 1 cubic meter per second) in spring 2003 at the Johnson Ranch gaging station on the Rio Grande in Big Bend National Park. The total number of fish species collected at all three sites (Boquillas, Johnson Ranch, and Santa Elena) in 1999 was greater than in 2004. The number of fish species collected at the Boquillas site in 1999 (10) was twice that collected in 2004; the number of species collected at the Johnson Ranch site in 1999 (nine) was almost twice that collected in 2004 (five). In contrast, the numbers at the Santa Elena site were nearly the same, 15 species in 1999, 14 in 2004. Percent community similarity for the Boquillas site is 8.04, for the Johnson Ranch site, 6.65, and for the Santa Elena site, 47.6, which indicates considerably more similarity between the 1999 and 2004 fish communities at the Santa Elena site than for the Boquillas and Johnson Ranch sites. At the Boquillas and Johnson Ranch sites, the fish communities shifted from small minnow (Cyprinidae) dominated in 1999 to largely gar (Lepisosteidae) and catfish (Ictaluridae) dominated in 2004. In contrast, no such shift occurred at the Santa Elena site between 1999 and 2004. Differences in flow conditions between the two downstream sites and the Santa Elena site might account for the dissimilar findings. The findings of the study provide some evidence that the spring 2003 period of low flow affected fish communities, but the findings are not definitive as other factors such as increased salinity

  19. Construction, Modeling and Testing of a Low-Flow, Large-Diameter Aerosol Flow System for the Study of the Formation and Reactions of Tropospheric Aerosols

    NASA Astrophysics Data System (ADS)

    Ezell, M. J.; Johnson, S. N.; Yu, Y.; Pokkunuri, P.; Perraud, V.; Bruns, E.; Alexander, M.; Zelenyuk, A.; Dabdub, D.; Finlayson-Pitts, B. J.

    2008-12-01

    A unique, high-volume, low-flow, stainless steel aerosol flow system for the study of the formation and reactions of aerosols relevant to the troposphere has been constructed, modeled and experimentally tested. The total flow tube length is 7.3 m which includes a 1.2 m section used for mixing. The flow tube is equipped with ultraviolet lamps for photolysis. The diameter of 0.45 m results in a smaller surface to volume ratio than is found in many other flow systems and reduces the contribution of wall reactions. The latter is also reduced by frequent cleaning of the flow tube walls which is feasible due to the ease of disassembly of the flow tube. Flow systems present a major advantage over chamber studies in that continuous sampling under stable conditions over long periods of time is possible, increasing the amount of sample available for analysis and permitting a wide variety of analytical techniques to be applied simultaneously. In this system, the large volume (1000 L) and low flow speed (2 cm/minute) result in a residence time of nearly an hour; and equally spaced sampling ports allow for time-resolved measurements of aerosol and gas-phase products. The central features of this system have been modeled using computational fluid dynamics software and experimentally probed using inert gases and aerosols. Instrumentation attached directly to this flow system includes a NOx analyzer, an ozone analyzer, relative humidity and temperature probes, a scanning mobility particle sizer (SMPS) spectrometer, an aerodynamic particle sizer (APS) spectrometer, GC-MS, integrating nephelometer, and FTIR. Particles are collected using impactors and filters, and analyzed by a variety of techniques including FTIR, electrospray ionization mass spectrometry (ESI-MS), atmospheric pressure chemical ionization mass spectrometry (APCI-MS), GC-MS, HPLC-UV and HPLC-MS. In addition, for selected studies, an aerosol mass spectrometer (AMS), a single particle mass spectrometer (SPLAT II) and

  20. The origin of high and low flows in the river Rhine: particle tracing and water quality calculations in a distributed hydrological model

    NASA Astrophysics Data System (ADS)

    Schellekens, Jaap; van Gils, Jos; Christophe, Christophe; Sperna-Weiland, Frederiek; Winsemius, Hessel

    2013-04-01

    The ability to quickly link a complete water quality model to any distributed hydrological model can be of great value. It provides the hydrological modeller with more information on the performance of the model by being able to add particle tracing and independent mass balance calculations to an existing distributed hydrological model. It also allows for full catchment water quality calculations forced by emissions to different hydrological compartments, taking into account the relevant processes in the different compartments of the hydrological model. A combined distributed hydrological model and hydrochemical model (Delwaq) have been combined within the modeling framework OpenStreams to model large scale hydrological processes in the Rhine basin upstream of the Dutch border at Lobith. Several models have been setup to evaluate (1) the origin of high and low flows in the Rhine basin based on subcatchment contribution and (2) the contribution of different land covers to the total flow with special reference to urban land cover. In addition (3) the relative share of fast and slow runoff components in the total river discharge has been quantified, as well as the age of these two fractions, both as a function of time. Finally (4) the transmission of a pollutant released in infiltrating water and undergoing sorption has been simulated, as a first test for implementing full water quality modelling. The results of a thirty-five year run using daily time steps for 1975 to 2010 were analysed for monthly average contribution to the total flow of each subcatchment and the different land cover types both for average flow conditions and for the top ten and bottom ten flow percentiles. Furthermore, a number of high and low flow events have been analysed in detail. They reveal the large contribution of the basin area upstream of Basel to the dry season flow, especially during the driest summers. Flood conditions in the basin have a more varied origin with the Moselle being the

  1. Coupling catchment hydrology and transient storage to model the fate of solutes during low-flow conditions of an upland river

    NASA Astrophysics Data System (ADS)

    Trévisan, D.; Periáñez, R.

    2016-03-01

    The residence time of solutes in catchments is longer during low-flow conditions, due to the lengthening of transport routes and the decrease in transfer velocities. In rivers, transient storage depends largely on exchanges with channel storage and the hyporheic zone and reflects the capacity of the river to buffer pollutant loads before they enter the aquatic environment of final receptors. Our objective was to evaluate the fate of solutes along a typical confined river of upland catchments. First, we calculate lateral inflows using a variable-source hydrology approach. Then, water motion and quality in the river channel are predicted by combining hydrodynamics and exchanges with channel storage and the hyporheic zone. The model is mainly parametrized from literature data during baseflow conditions to mimic the fate of adsorptive and non-persistent pollutants. Residence time in surface water, channel storage and the hyporheic zone were found to be sensitive to lateral inflows from groundwater seepage. Channel storage is the main process controlling residence time in upstream conditions, where the riverbed is mainly composed of stones and bedrock. Downstream, along with the formation of sediment deposits and riffle-pool units, hyporheic exchanges also control the lag time in the transfer of solutes. By integrating physically-based processes, the number of parameters is small, but the model still requires a detailed description of stream geometry and morphology. It can be used to evaluate stream restoration or catchment-river management when detailed data of stream geometry and morphology are available.

  2. Analysis of river pollution data from low-flow period by means of multivariate techniques: a case study from the oil-shale industry region, northeastern Estonia.

    PubMed

    Truu, Jaak; Heinaru, Eeva; Talpsep, Ene; Heinaru, Ain

    2002-01-01

    The oil-shale industry has created serious pollution problems in northeastern Estonia. Untreated, phenol-rich leachate from semi-coke mounds formed as a by-product of oil-shale processing is discharged into the Baltic Sea via channels and rivers. An exploratory analysis of water chemical and microbiological data sets from the low-flow period was carried out using different multivariate analysis techniques. Principal component analysis allowed us to distinguish different locations in the river system. The riverine microbial community response to water chemical parameters was assessed by co-inertia analysis. Water pH, COD and total nitrogen were negatively related to the number of biodegradative bacteria, while oxygen concentration promoted the abundance of these bacteria. The results demonstrate the utility of multivariate statistical techniques as tools for estimating the magnitude and extent of pollution based on river water chemical and microbiological parameters. An evaluation of river chemical and microbiological data suggests that the ambient natural attenuation mechanisms only partly eliminate pollutants from river water, and that a sufficient reduction of more recalcitrant compounds could be achieved through the reduction of wastewater discharge from the oil-shale chemical industry into the rivers. PMID:12638742

  3. Discharge and water-quality data for selected streams at low flow including some bottom-material analyses, and limnological study of six lakes, Westchester County, New York

    USGS Publications Warehouse

    Archer, Roger J.; Turk, John T.

    1977-01-01

    Water-quality data collected at sites on 33 Westchester County, N.Y., streams August 4 to 6, 1976 during low flow (80-percent or more duration) indicate that although the chemical characteristics of most streams met State standards for water-supply source waters, none met the coliform standard, and several failed to meet standards for organic nitrogen, pH, and dissolved oxygen. Chemical analyses of bottom materials indicated detectable concentrations of the insecticides chlordane, dieldrin, and DDT at most of the 17 stream sites sampled. Polychlorinated biphenyls(PCB's) were found in more than half the samples, and the lead concentration on one stream was significantly higher than at the other sites. The six lakes studied are similar in bedrock geology, climate, and algal types and numbers. Minor differences in the chemistry of the lakes is attributable to the presence or absence of marble (calcium carbonate) in the gneissic basins, septic loadings of soluble constituents, or runoff containing salt from winter road deicing. The lakes probably receive most of their water by direct runoff and groundwater seepage rather than from major streams. All six lakes can be classed as eutrophic on the basis of algal type and density, dissolved-oxygen distribution, and nitrogen and phosphorus concentrations. (Woodard-USGS)

  4. Estimating average base flow at low-flow partial-record stations on the south shore of Long Island, New York

    USGS Publications Warehouse

    Buxton, H.T.

    1985-01-01

    Base flows of the 29 major streams in southeast Nassau and southwest Suffolk Counties, New York, were statistically analyzed to discern the correlation among flows of adjacent streams. Concurrent base-flow data from a partial-record and a nearby continuous-record station were related; the data were from 1968-75, a period near hydrologic equilibrium on Long Island. The average base flow at each partial-record station was estimated from a regression equation and average measured base flow for the period at the continuous-record stations. Regression analyses are presented for the 20 streams with partial-record stations. Average base flow of the nine streams with a continuous record totaled 90 cu ft/sec; the predicted average base flow for the 20 streams with a partial record was 73 cu ft/sec (with a 95% confidence interval of 63 to 84 cu ft/sec.) Results indicate that this method provides reliable estimates of average low flow for streams such as those on Long Island, which consist mostly of base flow and are geomorphically similar. (USGS)

  5. Concentrations and loads of PCBs, dioxins, PAHs, PBDEs, OC pesticides and pyrethroids during storm and low flow conditions in a small urban semi-arid watershed.

    PubMed

    Gilbreath, Alicia N; McKee, Lester J

    2015-09-01

    Urban runoff has been identified in water quality policy documents for San Francisco Bay as a large and potentially controllable source of pollutants. In response, concentrations of suspended sediments and a range of trace organic pollutants were intensively measured in dry weather and storm flow runoff from a 100% urban watershed. Flow in this highly urban watershed responded very quickly to rainfall and varied widely resulting in rapid changes of turbidity, suspended sediments and pollutant concentrations. Concentrations of each organic pollutant class were within similar ranges reported in other studies of urban runoff, however comparison was limited for several of the pollutants given information scarcity. Consistently among PCBs, PBDEs, and PAHs, the more hydrophobic congeners were transported in larger proportions during storm flows relative to low flows. Loads for Water Years 2007-2010 were estimated using regression with turbidity during the monitored months and a flow weighted mean concentration for unmonitored dry season months. More than 91% of the loads for every pollutant measured were transported during storm events, along with 87% of the total discharge. While this dataset fills an important local data gap for highly urban watersheds of San Francisco Bay, the methods, the uniqueness of the analyte list, and the resulting interpretations have applicability for managing pollutant loads in urban watersheds in other parts of the world. PMID:25955693

  6. The impact of climate change on water provision under a low flow regime: a case study of the ecosystems services in the Francoli river basin.

    PubMed

    Marquès, Montse; Bangash, Rubab Fatima; Kumar, Vikas; Sharp, Richard; Schuhmacher, Marta

    2013-12-15

    Mediterranean basin is considered one of the most vulnerable regions of the world to climate change and with high probability to face acute water scarcity problem in the coming years. Francolí River basin (NE Spain), located in this vulnerable region is selected as a case study to evaluate the impact of climate change on the delivery of water considering the IPCC scenarios A2 and B1 for the time spans 2011-2040, 2041-2070 and 2071-2100. InVEST model is applied in a low flow river as a new case study, which reported successful results after its model validation. The studied hydrological ecosystem services will be highly impacted by climate change at Francolí River basin. Water yield is expected to be reduced between 11.5 and 44% while total drinking water provisioning will decrease between 13 and 50% having adverse consequences on the water quality of the river. Focusing at regional scale, Prades Mountains and Brugent Tributary provide most of the provision of water and also considered highly vulnerable areas to climate change. However, the most vulnerable part is the northern area which has the lowest provision of water. Francolí River basin is likely to experience desertification at this area drying Anguera and Vallverd tributaries. PMID:23958138

  7. Shear Dependent Adhesion of Leukocytes and Lectins to the Endothelium and Concurrent Changes in Thickness of the Glycocalyx of Post-capillary Venules in the Low Flow State

    PubMed Central

    Lipowsky, Herbert H.; Lescanic, Anne

    2012-01-01

    Objectives To elucidate shear dependent effects of deformation of the endothelial glycocalyx on adhesion of circulating ligands in post-capillary venules, and delineate effect of matrix metalloproteases (MMPs). Methods Adhesion of leukocytes (WBCs) and lectin-coated fluorescently labeled microspheres (FLMs, 0.1 μm diameter), to endothelium (EC) of post-capillary venules in mesentery was examined during acute reductions in shear rates (γ̇, hemorrhagic hypotension). Adhesion was examined with or without superfusion with 0.5 μM doxycycline to inhibit MMPs. Thickness of the glycocalyx was measured by exclusion of fluorescent 70 kDa dextran from the EC surface. Results During superfusion with Ringers, rapid reductions in γ̇ resulted in a significant rise in WBC adhesion and a two-fold rise in microsphere adhesion. With addition of doxycycline WBC and FLM adhesion increased two-fold under high and low flow conditions. FLM adhesion was invariant with γ̇ throughout the network in the normal (high) flow state. With reductions in γ̇, thickness of the glycocalyx increased significantly, with or without doxycycline. Conclusions The concurrent increase in WBC and FLM adhesion with increased thickness of the glycocalyx during reductions in shear suggests that glycocalyx core proteins recoil from their deformed steady state configuration, which increases exposure of binding sites for circulating ligands. PMID:22963321

  8. Calibration of a rainfall-runoff model at regional scale by optimising river discharge statistics: Performance analysis for the average/low flow regime

    NASA Astrophysics Data System (ADS)

    Lombardi, Laura; Toth, Elena; Castellarin, Attilio; Montanari, Alberto; Brath, Armando

    Traditional procedures for rainfall-runoff model calibration are generally based on the fit of individual values of simulated and observed hydrographs. We use here an alternative option that is carried out by matching, in the optimisation process, a set of streamflow statistics. Such an approach has the significant advantage to enable also a straightforward regional calibration of model parameters, based on the regionalisation of the selected statistics. The minimisation of the set of objective functions is carried out by using the AMALGAM algorithm, leading to the identification of behavioural parameter sets. The procedure is applied to a set of river basins located in central Italy: the basins are treated alternatively as gauged and ungauged and, as a term of comparison, the results obtained with a traditional time-domain calibration are also presented. With respect to previous applications of analogous procedures, we investigate here the identification of the target statistics depending on the purposes of the application, and in particular when the focus is on the reproduction of the low-flows. The results show that a suitable choice of the statistics to be optimised leads to interesting results in real world case studies as far as the reproduction of the different flow regimes is concerned.

  9. Subtraction CT with Low-Flow-Rate Arterial Contrast Injection to Estimate Drug Distribution During Balloon-Occluded Arterial Chemotherapy Infusion for Bladder Cancer

    SciTech Connect

    Mori, Kensaku; Yoshioka, Hiroshi; Nakajima, Kotaro; Irie, Toshiyuki; Sugahara, Shinji; Nozawa, Kumiko; Saida, Yukihisa; Itai, Yuji; Ishikawa, Satoru; Hayashi, Hitoshi

    2000-03-15

    Purpose: To simulate drug distribution during balloon-occluded arterial chemotherapy infusion (BOAI) for urinary bladder cancer using subtraction computed tomography (CT) with low-flow-rate arterial contrast injection (S-CTLA).Methods: Ten patients with bladder cancer underwent S-CTLA, and the distribution of contrast agent during BOAI into both internal iliac arteries simultaneously was evaluated in nine pairs of internal iliac arteries and one single artery. For S-CTLA, spiral CT data were acquired before and after 0.2 ml/sec intraarterial injection of contrast material. The enhancement of the urinary bladder wall, the gluteal muscles, and the pelvic bones was categorized using a 4-grade scale. The grades were compared in each of the three pelvic components and differences were tested for significance using the Wilcoxon test for paired groups.Results: S-CTLA revealed the distribution of the contrast agent clearly. Gluteal muscles grades were significantly higher than those of the other two assessed components.Conclusion: BOAI does not improve the concentration of contrast agent to the bladder wall over neighboring structures, suggesting that the balloon occlusion technique does not achieve its desired goal for chemotherapy targeting.

  10. Study on critical heat flux enhancement in flow boiling of SiC nano-fluids under low pressure and low flow conditions

    SciTech Connect

    Lee, S. W.; Park, S. D.; Kang, S.; Kim, S. M.; Seo, H.; Lee, D. W.; Bang, I. C.

    2012-07-01

    Critical heat flux (CHF) is the thermal limit of a phenomenon in which a phase change occurs during heating (such as bubbles forming on a metal surface used to heat water), which suddenly decreases the heat transfer efficiency, thus causing localized overheating of the heating surface. The enhancement of CHF can increase the safety margins and allow operation at higher heat fluxes; thus, it can increase the economy. A very interesting characteristics of nano-fluids is their ability to significantly enhance the CHF. nano-fluids are nano-technology-based colloidal dispersions engineered through stable suspending of nanoparticles. All experiments were performed in round tubes with an inner diameter of 0.01041 m and a length of 0.5 m under low pressure and low flow (LPLF) conditions at a fixed inlet temperature using water, 0.01 vol. % Al{sub 2}O{sub 3}/water and SiC/water nano-fluids. It was found that the CHF of the nano-fluids was enhanced and the CHF of the SiC/water nano-fluid was more enhanced than that of the Al{sub 2}O{sub 3}/water nano-fluid. (authors)

  11. Development of a novel low-flow ion source/sampling cone geometry for inductively coupled plasma mass spectrometry and application in hyphenated techniques

    NASA Astrophysics Data System (ADS)

    Pfeifer, Thorben; Janzen, Rasmus; Steingrobe, Tobias; Sperling, Michael; Franze, Bastian; Engelhard, Carsten; Buscher, Wolfgang

    2012-10-01

    A novel ion source/sampling cone device for inductively coupled plasma mass spectrometry (ICP-MS) especially operated in the hyphenated mode as a detection system coupled with different separation modules is presented. Its technical setup is described in detail. Its main feature is the very low total argon consumption of less than 1.5 L min- 1, leading to significant reduction of operational costs especially when time-consuming speciation analysis is performed. The figures of merit of the new system with respect to sensitivity, detection power, long-term stability and working range were explored. Despite the profound differences of argon consumption of the new system in comparison to the conventional ICP-MS system, many of the characteristic features of the conventional ICP-MS could be maintained to a great extent. To demonstrate the ion source's capabilities, it was used as an element-selective detector for gas (GC) and high performance liquid chromatography (HPLC) where organic compounds of mercury and cobalt, respectively, were separated and detected with the new low-flow ICP-MS detection system. The corresponding chromatograms are shown. The applicability for trace element analysis has been validated with the certified reference material NIST 1643e.

  12. Variation in aluminum, iron, and particle concentrations in oxic ground-water samples collected by use of tangential-flow ultrafiltration with low-flow sampling

    USGS Publications Warehouse

    Szabo, Z.; Oden, J.H.; Gibs, J.; Rice, D.E.; Ding, Y.

    2001-01-01

    Particulates that move with ground water and those that are artificially mobilized during well purging could be incorporated into water samples during collection and could cause trace-element concentrations to vary in unfiltered samples, and possibly in filtered samples (typically 0.45-um (micron) pore size) as well, depending on the particle-size fractions present. Therefore, measured concentrations may not be representative of those in the aquifer. Ground water may contain particles of various sizes and shapes that are broadly classified as colloids, which do not settle from water, and particulates, which do. In order to investigate variations in trace-element concentrations in ground-water samples as a function of particle concentrations and particle-size fractions, the U.S. Geological Survey, in cooperation with the U.S. Air Force, collected samples from five wells completed in the unconfined, oxic Kirkwood-Cohansey aquifer system of the New Jersey Coastal Plain. Samples were collected by purging with a portable pump at low flow (0.2-0.5 liters per minute and minimal drawdown, ideally less than 0.5 foot). Unfiltered samples were collected in the following sequence: (1) within the first few minutes of pumping, (2) after initial turbidity declined and about one to two casing volumes of water had been purged, and (3) after turbidity values had stabilized at less than 1 to 5 Nephelometric Turbidity Units. Filtered samples were split concurrently through (1) a 0.45-um pore size capsule filter, (2) a 0.45-um pore size capsule filter and a 0.0029-um pore size tangential-flow filter in sequence, and (3), in selected cases, a 0.45-um and a 0.05-um pore size capsule filter in sequence. Filtered samples were collected concurrently with the unfiltered sample that was collected when turbidity values stabilized. Quality-assurance samples consisted of sequential duplicates (about 25 percent) and equipment blanks. Concentrations of particles were determined by light scattering

  13. Estimating Locations of Perennial Streams in Idaho Using a Generalized Least-Squares Regression Model of 7-Day, 2-Year Low Flows

    USGS Publications Warehouse

    Wood, Molly S.; Rea, Alan; Skinner, Kenneth D.; Hortness, Jon E.

    2009-01-01

    Many State and Federal agencies use information regarding the locations of streams having intermittent or perennial flow when making management and regulatory decisions. For example, the application of some Idaho water quality standards depends on whether streams are intermittent. Idaho Administrative Code defines an intermittent stream as one having a 7-day, 2-year low flow (7Q2) less than 0.1 ft3/s. However, there is a general recognition that the cartographic representation of perennial/intermittent status of streams on U.S. Geological Survey (USGS) topographic maps is not as accurate or consistent as desirable from one map to another, which makes broad management and regulatory assessments difficult and inconsistent. To help resolve this problem, the USGS has developed a methodology for predicting the locations of perennial streams based on regional generalized least-squares (GLS) regression equations for Idaho streams for the 7Q2 low-flow statistic. Using these regression equations, the 7Q2 streamflow may be estimated for naturally flowing streams in most areas in Idaho. The use of these equations in conjunction with a geographic information system (GIS) technique known as weighted flow accumulation allows for an automated and continuous estimation of 7Q2 streamflow at all points along stream reaches. The USGS has developed a GIS-based map of the locations of streams in Idaho with perennial flow based on a 7Q2 of 0.1 ft3/s and a transition zone of plus or minus 1 standard error. Idaho State cooperators plan to use this information to make regulatory and water-quality management decisions. Originally, 7Q2 equations were developed for eight regions of similar hydrologic characteristics in the study area, using long-term data from 234 streamflow-gaging stations. Equations in five of the regions were revised based on spatial patterns observed in the initial perennial streams map and unrealistic behavior of the equations in extrapolation. The standard errors of

  14. Low flow oxygen therapy from a portable oxygen concentrator or an oxygen cylinder effectively treats hypoxemia in anesthetized white-tailed deer (Odocoileus virginianus).

    PubMed

    Fahlman, Asa; Caulkett, Nigel; Woodbury, Murray; Duke-Novakovski, Tanya; Wourms, Vincent

    2014-06-01

    For treatment of hypoxemia, delivery of the minimum effective oxygen flow rate is advantageous during field anesthesia because it prolongs the life of the oxygen cylinder. Portable oxygen concentrators as the oxygen source require less logistical considerations than cylinders and are a safer alternative during helicopter field work because they are nonexplosive devices. The objective of this study was to evaluate low oxygen flow rates by continuous or pulsed intranasal delivery for treatment of hypoxemia in anesthetized white-tailed deer (Odocoileus virginianus). Nine captive adult female deer (body mass 56-72 kg) were physically restrained in a drop-floor chute and hand injected intramuscularly with medetomidine (0.1-0.14 mg/kg) and ketamine (2.5-4.3 mg/kg). Intranasal oxygen was delivered from an oxygen cylinder at continuous flow rates of 1 and 2 L/min or from a battery driven oxygen concentrator (EverGo Portable Oxygen Concentrator, Respironics) with pulse-dose delivery (maximum capacity of 1.05 L/min). The pulse-dose setting (pulse volume 12-70 ml) was adjusted according to the respiratory rate. Arterial blood gases were analyzed before, during, and after O2 supplementation. A 10-min washout period was allowed between treatment groups. All three treatments adequately treated hypoxemia. The partial pressure of arterial oxygenation increased significantly from baseline values of 55 +/- 10 to 115 +/- 31 mm Hg during supplementation from the oxygen concentrator, to 138 +/- 21 mm Hg during supplementation from the oxygen cylinder at 1 L/min, and to 201 +/- 42 mm Hg at 2 L/min. In conclusion, low flow rates of intranasal oxygen supplemented continuously from an oxygen cylinder or by pulsed delivery from a portable oxygen concentrator effectively treated hypoxemia in anesthetized white-tailed deer. PMID:25000687

  15. Detection of water quality trends at high, median, and low flow in a Catskill Mountain stream, New York, through a new statistical method

    NASA Astrophysics Data System (ADS)

    Murdoch, Peter S.; Shanley, James B.

    2006-08-01

    The effects of changes in acid deposition rates resulting from the Clean Air Act Amendments of 1990 should first appear in stream waters during rainstorms and snowmelt, when the surface of the watershed is most hydrologically connected to the stream. Early detection of improved stream water quality is possible if trends at high flow could be separately determined. Trends in concentrations of sulfate (SO42-), nitrate (NO3-), calcium plus magnesium (Ca2++Mg2+), and acid-neutralizing capacity (ANC) in Biscuit Brook, Catskill Mountains, New York, were assessed through segmented regression analysis (SRA). The method uses annual concentration-to-discharge relations to predict concentrations for specific discharges, then compares those annual values to determine trends at specific discharge levels. Median-flow trends using SRA were comparable to those predicted by the seasonal Kendall tau test and a multiple regression residual analysis. All of these methods show that stream water SO42- concentrations have decreased significantly since 1983; Ca2++Mg2+ concentrations have decreased at a steady but slower rate than SO42-; and ANC shows no trend. The new SRA method, however, reveals trends that differ at specified flow levels. ANC has increased, and NO3- concentrations have decreased at high flows, but neither has changed as significantly at low flows. The general downward trend in SO42- flattened at median flow and reversed at high flow between 1997 and 2002. The reversal of the high-flow SO42- trend is consistent with increases in SO42- concentrations in both precipitation and soil solutions at Biscuit Brook. Separate calculation of high-flow trends provides resource managers with an early detection system for assessing changes in water quality resulting from changes in acidic deposition.

  16. Source and fate of inorganic solutes in the Gibbon River, Yellowstone National Park, Wyoming, USA. I. Low-flow discharge and major solute chemistry

    NASA Astrophysics Data System (ADS)

    McCleskey, R. Blaine; Nordstrom, D. Kirk; Susong, David D.; Ball, James W.; Holloway, JoAnn M.

    2010-06-01

    The Gibbon River in Yellowstone National Park (YNP) is an important natural resource and habitat for fisheries and wildlife. However, the Gibbon River differs from most other mountain rivers because its chemistry is affected by several geothermal sources including Norris Geyser Basin, Chocolate Pots, Gibbon Geyser Basin, Beryl Spring, and Terrace Spring. Norris Geyser Basin is one of the most dynamic geothermal areas in YNP, and the water discharging from Norris is much more acidic (pH 3) than other geothermal basins in the upper-Madison drainage (Gibbon and Firehole Rivers). Water samples and discharge data were obtained from the Gibbon River and its major tributaries near Norris Geyser Basin under the low-flow conditions of September 2006. Surface inflows from Norris Geyser Basin were sampled to identify point sources and to quantify solute loading to the Gibbon River. The source and fate of the major solutes (Ca, Mg, Na, K, SiO 2, Cl, F, HCO 3, SO 4, NO 3, and NH 4) in the Gibbon River were determined in this study and these results may provide an important link in understanding the health of the ecosystem and the behavior of many trace solutes. Norris Geyser Basin is the primary source of Na, K, Cl, SO 4, and N loads (35-58%) in the Gibbon River. The largest source of HCO 3 and F is in the lower Gibbon River reach. Most of the Ca and Mg originate in the Gibbon River upstream from Norris Geyser Basin. All the major solutes behave conservatively except for NH 4, which decreased substantially downstream from Gibbon Geyser Basin, and SiO 2, small amounts of which precipitated on mixing of thermal drainage with the river. As much as 9-14% of the river discharge at the gage is from thermal flows during this period.

  17. Detection of water quality trends at high, median, and low flow in a Catskill Mountain stream, New York, through a new statistical method

    USGS Publications Warehouse

    Murdoch, Peter S.; Shanley, J.B.

    2006-01-01

    The effects of changes in acid deposition rates resulting from the Clean Air Act Amendments of 1990 should first appear in stream waters during rainstorms and snowmelt, when the surface of the watershed is most hydrologically connected to the stream. Early detection of improved stream water quality is possible if trends at high flow could be separately determined. Trends in concentrations of sulfate (8042-), nitrate (NO3-), calcium plus magnesium (Ca2++Mg 2+), and acid-neutralizing capacity (ANC) in Biscuit Brook, Catskill Mountains, New York, were assessed through segmented regression analysis (SRA). The method uses annual concentration-to-discharge relations to predict concentrations for specific discharges, then compares those annual values to determine trends at specific discharge levels. Median-flow trends using SRA were comparable to those predicted by the seasonal Kendall tau test and a multiple regression residual analysis. All of these methods show that stream water SO42- concentrations have decreased significantly since 1983; Ca2++Mg2+ concentrations have decreased at a steady but slower rate than SO42-; and ANC shows no trend. The new SRA method, however, reveals trends that differ at specified flow levels. ANC has increased, and NO3- concentrations have decreased at high flows, but neither has changed as significantly at low flows. The general downward trend in SO42- flattened at median flow and reversed at high flow between 1997 and 2002. The reversal of the high-flow SO42- trend is consistent with increases in SO 42- concentrations in both precipitation and soil solutions at Biscuit Brook. Separate calculation of high-flow trends provides resource managers with an early detection system for assessing changes in water quality resulting from changes in acidic deposition. Copyright 2006 by the American Geophysical Union.

  18. Development and Evaluation of an Externally Air-Cooled Low-Flow torch and the Attenuation of Space Charge and Matrix Effects in Inductively Coupled Plasma Mass Spectrometry

    SciTech Connect

    Praphairaksit, N.

    2000-09-12

    An externally air-cooled low-flow torch has been constructed and successfully demonstrated for applications in inductively coupled plasma mass spectrometry (ICP-MS). The torch is cooled by pressurized air flowing at {approximately}70 L/min through a quartz air jacket onto the exterior of the outer tube. The outer gas flow rate and operating RF forward power are reduced considerably. Although plasmas can be sustained at the operating power as low as 400 W with a 2 L/min of outer gas flow, somewhat higher power and outer gas flows are advisable. A stable and analytical useful plasma can be obtained at 850 W with an outer gas flow rate of {approximately}4 L/min. Under these conditions, the air-cooled plasma produces comparable sensitivities, doubly charged ion ratios, matrix effects and other analytical merits as those produced by a conventional torch while using significantly less argon and power requirements. Metal oxide ion ratios are slightly higher with the air-cooled plasma but can be mitigated by reducing the aerosol gas flow rate slightly with only minor sacrifice in analyte sensitivity. A methodology to alleviate the space charge and matrix effects in ICP-MS has been developed. A supplemental electron source adapted from a conventional electron impact ionizer is added to the base of the skimmer. Electrons supplied from this source downstream of the skimmer with suitable amount and energy can neutralize the positive ions in the beam extracted from the plasma and diminish the space charge repulsion between them. As a result, the overall ion transmission efficiency and consequent analyte ion sensitivities are significantly improved while other important analytical aspects, such as metal oxide ion ratio, doubly charged ion ratio and background ions remain relatively unchanged with the operation of this electron source. This technique not only improves the ion transmission efficiency but also minimizes the matrix effects drastically. The matrix-induced suppression

  19. Variation in aluminum, iron, and particle concentrations in oxic groundwater samples collected by use of tangential-flow ultrafiltration with low-flow sampling

    NASA Astrophysics Data System (ADS)

    Szabo, Zoltan; Oden, Jeannette H.; Gibs, Jacob; Rice, Donald E.; Ding, Yuan

    2002-02-01

    Particulates that move with ground water and those that are artificially mobilized during well purging could be incorporated into water samples during collection and could cause trace-element concentrations to vary in unfiltered samples, and possibly in filtered samples (typically 0.45-um (micron) pore size) as well, depending on the particle-size fractions present. Therefore, measured concentrations may not be representative of those in the aquifer. Ground water may contain particles of various sizes and shapes that are broadly classified as colloids, which do not settle from water, and particulates, which do. In order to investigate variations in trace-element concentrations in ground-water samples as a function of particle concentrations and particle-size fractions, the U.S. Geological Survey, in cooperation with the U.S. Air Force, collected samples from five wells completed in the unconfined, oxic Kirkwood-Cohansey aquifer system of the New Jersey Coastal Plain. Samples were collected by purging with a portable pump at low flow (0.2-0.5 liters per minute and minimal drawdown, ideally less than 0.5 foot). Unfiltered samples were collected in the following sequence: (1) within the first few minutes of pumping, (2) after initial turbidity declined and about one to two casing volumes of water had been purged, and (3) after turbidity values had stabilized at less than 1 to 5 Nephelometric Turbidity Units. Filtered samples were split concurrently through (1) a 0.45-um pore size capsule filter, (2) a 0.45-um pore size capsule filter and a 0.0029-um pore size tangential-flow filter in sequence, and (3), in selected cases, a 0.45-um and a 0.05-um pore size capsule filter in sequence. Filtered samples were collected concurrently with the unfiltered sample that was collected when turbidity values stabilized. Quality-assurance samples consisted of sequential duplicates (about 25 percent) and equipment blanks. Concentrations of particles were determined by light scattering.

  20. Frequency noise in frequency swept fiber laser.

    PubMed

    Pedersen, Anders Tegtmeier; Rottwitt, Karsten

    2013-04-01

    This Letter presents a measurement of the spectral content of frequency shifted pulses generated by a lightwave synthesized frequency sweeper. We found that each pulse is shifted in frequency with very high accuracy. We also discovered that noise originating from light leaking through the acousto- optical modulators and forward propagating Brillouin scattering appear in the spectrum. PMID:23546253

  1. Robustness Analysis of Regional Water Supply Portfolios using Synthetic Inflow Scenarios with Variable Drought Frequency

    NASA Astrophysics Data System (ADS)

    Herman, J. D.; Zeff, H. B.; Lamontagne, J. R.; Reed, P. M.; Characklis, G. W.

    2015-12-01

    Robustness analyses of water supply systems have moved toward exploratory simulation to discover scenarios in which existing or planned policies may fail to meet stakeholder objectives. Such assessments rely heavily on the choice of plausible future scenarios, which, in the case of drought management, requires sampling or generating a broad ensemble of reservoir inflows which do not necessarily reflect the historical record. Here we adapt a widely used synthetic streamflow generation method to adjust the frequency of low-flow periods, which can be related to impactful historical events from the perspective of decision makers. Specifically, the modified generation procedure allows the user to specify parameters n, p such that events with observed weekly non-exceedance frequency p appear in the synthetic scenario with approximate frequency np (i.e., the pth percentile flow occurs n times more frequently). Additionally, the generator preserves the historical autocorrelation of streamflow and its seasonality, as well as approximate multi-site correlation. Using model simulations from recent work in multi-objective urban drought portfolio planning in North Carolina, a region whose water supply faces both climate and population pressures, we illustrate the decision-relevant consequences caused by raising the frequency of low flows associated with the 2007-2008 drought. This method explores system performance under extreme events of increasing frequency prior to reconciling these findings with climate model projections, and thus can be used to support bottom-up robustness methods in water systems planning.

  2. Estimation of minimum 7-day, 2-year discharge for selected stream sites, and associated low-flow water-quality data, southeast Texas, 1997-98

    USGS Publications Warehouse

    East, Jeffery W.

    1999-01-01

    The U.S. Geological Survey (USGS) operates a network of streamflow-gaging stations in Texas that provides discharge data used for water-management decisions and various other purposes. Operating stations at all locations where discharge data are needed is not feasible, but the statistical characteristics of the network station data can be used to estimate discharge characteristics at ungaged sites. Regionalization techniques such as regression analyses relate discharge-frequency characteristics to selected physical and climatic characteristics of drainage basins. A particular discharge-frequency characteristic that can be regionalized is the minimum 7-day, 2-year discharge1 (7Q2). In Texas, the 7Q2 is used at stream sites to analyze permit applications for water allocation, water-supply planning, aquatic maintenance (instream flow) requirements, and waste-load allocation for point and nonpoint source discharges.

  3. Prediction of regional streamflow frequency using model tree ensembles

    NASA Astrophysics Data System (ADS)

    Schnier, Spencer; Cai, Ximing

    2014-09-01

    This study introduces a novel data-driven method called model tree ensembles (MTEs) to predict streamflow frequency statistics based on known drainage area characteristics, which yields insights into the dominant controls of regional streamflow. The database used to induce the models contains both natural and anthropogenic drainage area characteristics for 294 USGS stream gages (164 in Texas and 130 in Illinois). MTEs were used to predict complete flow duration curves (FDCs) of ungaged streams by developing 17 models corresponding to 17 points along the FDC. Model accuracy was evaluated using ten-fold cross-validation and the coefficient of determination (R2). During the validation, the gages withheld from the analysis represent ungaged watersheds. MTEs are shown to outperform global multiple-linear regression models for predictions in ungaged watersheds. The accuracy of models for low flow is enhanced by explicit consideration of variables that capture human interference in watershed hydrology (e.g., population). Human factors (e.g., population and groundwater use) appear in the regionalizations for low flows, while annual and seasonal precipitation and drainage area are important for regionalizations of all flows. The results of this study have important implications for predictions in ungaged watersheds as well as gaged watersheds subject to anthropogenically-driven hydrologic changes.

  4. AUTOMATIC FREQUENCY CONTROL SYSTEM

    DOEpatents

    Hansen, C.F.; Salisbury, J.D.

    1961-01-10

    A control is described for automatically matching the frequency of a resonant cavity to that of a driving oscillator. The driving oscillator is disconnected from the cavity and a secondary oscillator is actuated in which the cavity is the frequency determining element. A low frequency is mixed with the output of the driving oscillator and the resultant lower and upper sidebands are separately derived. The frequencies of the sidebands are compared with the secondary oscillator frequency. deriving a servo control signal to adjust a tuning element in the cavity and matching the cavity frequency to that of the driving oscillator. The driving oscillator may then be connected to the cavity.

  5. Questa baseline and pre-mining ground-water quality investigation. 2. Low-flow (2001) and snowmelt (2002) synoptic/tracer water chemistry for the Red River, New Mexico

    USGS Publications Warehouse

    McCleskey, R. Blaine; Nordstrom, D. Kirk; Steiger, Judy I.; Kimball, Briant A.; Verplanck, Philip L.

    2003-01-01

    Water analyses are reported for 259 samples collected from the Red River, New Mexico, and its tributaries during low-flow(2001) and spring snowmelt (2002) tracer studies. Water samples were collected along a 20-kilometer reach of the Red River beginning just east of the town of Red River and ending at the U.S. Geological Survey streamflow-gaging station located east of Questa, New Mexico. The study area was divided into three sections where separate injections and synoptic sampling events were performed during the low-flow tracer study. During the spring snowmelt tracer study, three tracer injections and synoptic sampling events were performed bracketing the areas with the greatest metal loading into the Red River as determined from the low-flow tracer study. The lowflow tracer synoptic sampling events were August 17, 20, and 24, 2001. The synoptic sampling events for the spring snowmelt tracer were March 30, 31, and April 1, 2002. Stream and large inflow water samples were sampled using equal-width and depth-integrated sampling methods and composited into half-gallon bottles. Grab water samples were collected from smaller inflows. Stream temperatures were measured at the time of sample collection. Samples were transported to a nearby central processing location where pH and specific conductance were measured and the samples processed for chemical analyses. Cations, trace metals, iron redox species, and fluoride were analyzed at the U.S. Geological Survey laboratory in Boulder, Colorado. Cations and trace metal concentrations were determined using inductively coupled plasma-optical emission spectrometry and graphite furnace atomic absorption spectrometry. Arsenic concentrations were determined using hydride generation atomic absorption spectrometry, iron redox species were measured using ultraviolet-visible spectrometry, and fluoride concentrations were determined using an ion-selective electrode. Alkalinity was measured by automated titration, and sulfate

  6. Encoding voice fundamental frequency into vibrotactile frequency.

    PubMed

    Rothenberg, M; Molitor, R D

    1979-10-01

    Measured in this study was the ability of eight hearing and five deaf subjects to identify the stress pattern in a short sentence from the variation in voice fundamental frequency (F0), when presented aurally (for hearing subjects) and when transformed into vibrotactile pulse frequency. Various transformations from F0 to pulse frequency were tested in an attempt to determine an optimum transformation, the amount of F0 information that could be transmitted, and what the limitations in the tactile channel might be. The results indicated that a one- or two-octave reduction of F0 vibrotactile frequency (transmitting every second or third glottal pulse) might result in a significant ability to discriminate the intonation patterns associated with moderate-to-strong patterns of sentence stress in English. However, accurate reception of the details of the intonation pattern may require a slower than normal pronounciation because of an apparent temporal indeterminacy of about 200 ms in the perception of variations in vibrotactile frequency. A performance deficit noted for the two prelingually, profoundly deaf subjects with marginally discriminable encodings offers some support for our previous hypothesis that there is a natural association between auditory pitch and perceived vibrotactile frequency. PMID:159917

  7. Effects of low-flow diversions from the South Wichita River on downstream salinity of the South Wichita River, Lake Kemp, and the Wichita River, North Texas, October 1982-September 1992

    USGS Publications Warehouse

    Baldys, Stanley; Bush, Peter W.; Kidwell, Charles C.

    1996-01-01

    In parts of the upper reaches of the Red River Basin in Texas, streamflow is characterized by levels of salinity that limit its usefulness for most purposes. Large dissolved solids and dissolved chloride concentrations are caused primarily by flow from natural salt springs in tributaries to the Red River. To reduce downstream salinity in the Wichita River, a dam in the South Wichita River downstream of an area of salt springs (designated salinity source area VIII) diverts low flows (which are the most saline) to a manmade brine lake for evaporation. Statistical tests on salinity data for the South Wichita River, Lake Kemp, and the Wichita River for the period October 1982–September 1992 were done to determine the effects on downstream salinity of low-flow diversions from the South Wichita River that began in May 1987. Salinity in the South Wichita River downstream of the low-flow diversion structure was (statistically) significantly less during the 65-month period of record after diversion than during the 55- month period of record before diversion. Wilcoxon rank-sum tests yielded strong evidence that discharge-weighted dissolved solids and dischargeweighted dissolved chloride concentrations, as well as discharge-weighted specific conductance, were significantly less after diversion. Whether salinity in Lake Kemp had a significant downward trend during the period of record August 1989–August 1992 could not be determined conclusively from observed salinity data. Mann-Kendall trend tests yielded weak evidence that volume-weighted dissolved solids and dissolved chloride concentrations in Lake Kemp tended to decrease with time. However, serial correlation in the time series of salinity data could have adversely affected the test results. The significant effects of low-flow diversions on salinity in the South Wichita River are not discernible in the Wichita River downstream from Lake Kemp. Although salinity was significantly less downstream from Lake Kemp after

  8. Modeling Frequency Comb Sources

    NASA Astrophysics Data System (ADS)

    Li, Feng; Yuan, Jinhui; Kang, Zhe; Li, Qian; Wai, P. K. A.

    2016-06-01

    Frequency comb sources have revolutionized metrology and spectroscopy and found applications in many fields. Stable, low-cost, high-quality frequency comb sources are important to these applications. Modeling of the frequency comb sources will help the understanding of the operation mechanism and optimization of the design of such sources. In this paper,we review the theoretical models used and recent progress of the modeling of frequency comb sources.

  9. Frequency Response Tool

    2014-03-13

    According to the North American Electric Reliability Corporation (NERC) definition: “Frequency response is a measure of an Interconnection’s ability to stabilize frequency immediately following the sudden loss of generation or load, and is a critical component of the reliable operation of the Bulk-Power System, particularly during disturbances and recoveries. Failure to maintain frequency can disrupt the operation of equipment and initiate disconnection of power plant equipment to prevent it from being damaged, which could leadmore » to wide-spread blackouts.” Frequency Response Tool automates the power system frequency response analysis process. The tool performs initial estimation of the system frequency parameters (initial frequency, minimum frequency, settling point). User can visually inspect and adjust these parameters. The tool also calculates the frequency response performance metrics of the system, archives the historic events and baselines the system performance. Frequency response performance characteristics of the system are calculated using phasor measurement unit (PMU) information. Methodology of the frequency response performance assessment implemented in the tool complies with the NERC Frequency response standard.« less

  10. Eastern Frequency Response Study

    SciTech Connect

    Miller, N.W.; Shao, M.; Pajic, S.; D'Aquila, R.

    2013-05-01

    This study was specifically designed to investigate the frequency response of the Eastern Interconnection that results from large loss-of-generation events of the type targeted by the North American Electric Reliability Corp. Standard BAL-003 Frequency Response and Frequency Bias Setting (NERC 2012a), under possible future system conditions with high levels of wind generation.

  11. Frequency Response Tool

    SciTech Connect

    Etingov, Pavel; Chassin, PNNL David; Zhang, PNNL Yu; PNNL,

    2014-03-13

    According to the North American Electric Reliability Corporation (NERC) definition: “Frequency response is a measure of an Interconnection’s ability to stabilize frequency immediately following the sudden loss of generation or load, and is a critical component of the reliable operation of the Bulk-Power System, particularly during disturbances and recoveries. Failure to maintain frequency can disrupt the operation of equipment and initiate disconnection of power plant equipment to prevent it from being damaged, which could lead to wide-spread blackouts.” Frequency Response Tool automates the power system frequency response analysis process. The tool performs initial estimation of the system frequency parameters (initial frequency, minimum frequency, settling point). User can visually inspect and adjust these parameters. The tool also calculates the frequency response performance metrics of the system, archives the historic events and baselines the system performance. Frequency response performance characteristics of the system are calculated using phasor measurement unit (PMU) information. Methodology of the frequency response performance assessment implemented in the tool complies with the NERC Frequency response standard.

  12. Making Sense of Frequency.

    ERIC Educational Resources Information Center

    Larsen-Freeman, Diane

    2002-01-01

    Responds to Ellis (2002), which focuses on frequency in language processing, language use, and language acquisition. Contextualizes the frequency factor in terms of the evolution of second language acquisition (SLA) research. Suggests that although relevant and important, the frequency factor requires greater definition and qualification.…

  13. Frequency discriminator/phase detector

    NASA Technical Reports Server (NTRS)

    Crow, R. B.

    1974-01-01

    Circuit provides dual function of frequency discriminator/phase detector which reduces frequency acquisition time without adding to circuit complexity. Both frequency discriminators, in evaluated frequency discriminator/phase detector circuits, are effective two decades above and below center frequency.

  14. Diophantine frequency synthesis.

    PubMed

    Sotiriadis, Paul Peter

    2006-11-01

    A methodology for fine-step, fast-hopping, low-spurs phase-locked loop based frequency synthesis is presented. It uses mathematical properties of integer numbers and linear Diophantine equations to overcome the constraining relation between frequency step and phase-comparator frequency that is inherent in conventional phase-locked loop based frequency synthesis. The methodology leads to fine-step, fast-hopping, modular-structured frequency synthesizers with potentially very low spurs, especially in the vicinity of the carrier. The paper focuses on the mathematical principles of the new methodology and the related number theoretic algorithms. PMID:17091835

  15. Frequency selective infrared sensors

    DOEpatents

    Davids, Paul; Peters, David W

    2013-05-28

    A frequency selective infrared (IR) photodetector having a predetermined frequency band. The exemplary frequency selective photodetector includes: a dielectric IR absorber having a first surface and a second surface substantially parallel to the first surface; an electrode electrically coupled to the first surface of the dielectric IR absorber; and a frequency selective surface plasmonic (FSSP) structure formed on the second surface of the dielectric IR absorber. The FSSP structure is designed to selectively transmit radiation in the predetermined frequency band that is incident on the FSSP structure substantially independent of the angle of incidence of the incident radiation on the FSSP structure.

  16. Frequency selective infrared sensors

    DOEpatents

    Davids, Paul; Peters, David W

    2014-11-25

    A frequency selective infrared (IR) photodetector having a predetermined frequency band. The exemplary frequency selective photodetector includes: a dielectric IR absorber having a first surface and a second surface substantially parallel to the first surface; an electrode electrically coupled to the first surface of the dielectric IR absorber; and a frequency selective surface plasmonic (FSSP) structure formed on the second surface of the dielectric IR absorber. The FSSP structure is designed to selectively transmit radiation in the predetermined frequency band that is incident on the FSSP structure substantially independent of the angle of incidence of the incident radiation on the FSSP structure.

  17. Regional flood frequency analysis

    SciTech Connect

    Singh, V.P.

    1987-01-01

    This book, the fourth of a four volume set, contains five sections encompassing major aspects of regional flood frequency analysis. Each section starts usually with an invited state-of-the-art paper followed by contributed papers. The first section provides an assessment of regional flood frequency analysis. Methods for performing regional frequency analysis for ungaged watersheds are presented in Section 2. More discussion on regional frequency analysis is provided in Section 3. Selection and comparison of regional frequency methods are dealt with in Section 4; these are of great interest to the user. Increasing attention is being focused these days on paleohydrologic flood analysis. This topic is covered in Section 5.

  18. Harmonic Frequency Lowering

    PubMed Central

    Kirchberger, Martin

    2016-01-01

    A novel algorithm for frequency lowering in music was developed and experimentally tested in hearing-impaired listeners. Harmonic frequency lowering (HFL) combines frequency transposition and frequency compression to preserve the harmonic content of music stimuli. Listeners were asked to make judgments regarding detail and sound quality in music stimuli. Stimuli were presented under different signal processing conditions: original, low-pass filtered, HFL, and nonlinear frequency compressed. Results showed that participants reported perceiving the most detail in the HFL condition. In addition, there was no difference in sound quality across conditions. PMID:26834122

  19. Frequency dependent squeezed light at audio frequencies

    NASA Astrophysics Data System (ADS)

    Miller, John

    2015-04-01

    Following successful implementation in the previous generation of instruments, squeezed states of light represent a proven technology for the reduction of quantum noise in ground-based interferometric gravitational-wave detectors. As a result of lower noise and increased circulating power, the current generation of detectors places one further demand on this technique - that the orientation of the squeezed ellipse be rotated as function of frequency. This extension allows previously negligible quantum radiation pressure noise to be mitigated in addition to quantum shot noise. I will present the results of an experiment which performs the appropriate rotation by reflecting the squeezed state from a detuned high-finesse optical cavity, demonstrating frequency dependent squeezing at audio frequencies for the first time and paving the way for broadband quantum noise reduction in Advanced LIGO. Further, I will indicate how a realistic implementation of this approach will impact Advanced LIGO both alone and in combination with other potential upgrades.

  20. Radio frequency detection assembly and method for detecting radio frequencies

    SciTech Connect

    Cown, Steven H.; Derr, Kurt Warren

    2010-03-16

    A radio frequency detection assembly is described and which includes a radio frequency detector which detects a radio frequency emission produced by a radio frequency emitter from a given location which is remote relative to the radio frequency detector; a location assembly electrically coupled with the radio frequency detector and which is operable to estimate the location of the radio frequency emitter from the radio frequency emission which has been received; and a radio frequency transmitter electrically coupled with the radio frequency detector and the location assembly, and which transmits a radio frequency signal which reports the presence of the radio frequency emitter.

  1. Frequency conversion system

    NASA Technical Reports Server (NTRS)

    Sanders, Steven (Inventor); Waarts, Robert G. (Inventor)

    2001-01-01

    A frequency conversion system comprises first and second gain sources providing first and second frequency radiation outputs where the second gain source receives as input the output of the first gain source and, further, the second gain source comprises a Raman or Brillouin gain fiber for wave shifting a portion of the radiation of the first frequency output into second frequency radiation output to provided a combined output of first and second frequencies. Powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Raman/Brillouin amplifier or oscillator between the high power source and the NFM device. Further, polarization conversion using Raman or Brillouin wavelength shifting is provided to optimize frequency conversion efficiency in the NFM device.

  2. Low frequency cultural noise

    NASA Astrophysics Data System (ADS)

    Sheen, Dong-Hoon; Shin, Jin Soo; Kang, Tae-Seob; Baag, Chang-Eob

    2009-09-01

    Abnormal cultural seismic noise is observed in the frequency range of 0.01-0.05 Hz. Cultural noise generated by human activities is generally observed in frequencies above 1 Hz, and is greater in the daytime than at night. The low-frequency noise presented in this paper exhibits a characteristic amplitude variation and can be easily identified from time domain seismograms in the frequency range of interest. The amplitude variation is predominantly in the vertical component, but the horizontal components also show variations. Low-frequency noise is markedly periodic, which reinforces its interpretation as cultural noise. Such noise is observed world-wide, but is limited to areas in the vicinity of railways. The amplitude variation in seismograms correlates strongly with railway timetables, and the waveform shows a wavelength shift associated with the Doppler effect, which indicates that the origin of seismic background noise in the frequency range 0.01-0.05 Hz is railways.

  3. Frequency Response Analysis Tool

    SciTech Connect

    Etingov, Pavel V.; Kosterev, Dmitry; Dai, T.

    2014-12-31

    Frequency response has received a lot of attention in recent years at the national level, which culminated in the development and approval of North American Electricity Reliability Corporation (NERC) BAL-003-1 Frequency Response and Frequency Bias Setting Reliability Standard. This report is prepared to describe the details of the work conducted by Pacific Northwest National Laboratory (PNNL) in collaboration with the Bonneville Power Administration and Western Electricity Coordinating Council (WECC) Joint Synchronized Information Subcommittee (JSIS) to develop a frequency response analysis tool (FRAT). The document provides the details on the methodology and main features of the FRAT. The tool manages the database of under-frequency events and calculates the frequency response baseline. Frequency response calculations are consistent with frequency response measure (FRM) in NERC BAL-003-1 for an interconnection and balancing authority. The FRAT can use both phasor measurement unit (PMU) data, where available, and supervisory control and data acquisition (SCADA) data. The tool is also capable of automatically generating NERC Frequency Response Survey (FRS) forms required by BAL-003-1 Standard.

  4. Frequency selective terahertz retroreflectors

    NASA Astrophysics Data System (ADS)

    Williams, Richard James

    The use of novel optical structures operating at terahertz frequencies in industrial and military applications continues to grow. Some of these novel structures include gratings, frequency selective surfaces, metamaterials and metasurfaces, and retroreflectors. A retroreflector is a device that exhibits enhanced backscatter by concentrating the reflected wave in the direction of the source. Retroreflectors have applications in a variety of diverse fields such as aviation, radar systems, antenna technology, communications, navigation, passive identification, and metrology due to their large acceptance angles and frequency bandwidth. This thesis describes the design, fabrication, and characterization of a retroreflector designed for terahertz frequencies and the incorporation of a frequency selective surface in order to endow the retroreflector with narrow-band frequency performance. The radar cross section of several spherical lens reflectors operating at terahertz frequencies was investigated. Spherical lens reflectors with diameters ranging from 2 mm to 8 mm were fabricated from fused silica ball lenses and their radar cross section was measured at 100 GHz, 160 GHz, and 350 GHz. Crossed-dipole frequency selective surfaces exhibiting band-pass characteristics at 350 GHz fabricated from 12 um-thick Nickel screens were applied to the apertures of the spherical lens reflectors. The radar cross section of the frequency selective retroreflectors was measured at 160 GHz and 350 GHz to demonstrate proof-of-concept of narrow-band terahertz performance.

  5. Word frequency affects hypermnesia.

    PubMed

    Macie, K M; Larsen, J D

    1996-12-01

    Hypermnesia, the tendency of participants to recall more items from a list they have studied when they are asked to recall the list several times on a free-recall test, is enhanced by factors that lead to better performance on free-recall tests. This study tested the hypothesis that words which appear with high frequency in the English language would produce hypermnesia but that low frequency words would not. The activity the 57 participants were required to do between repeated recall tests was also manipulated but had no effect on the number of words recalled. High frequency words resulted in hypermnesia but low frequency words did not. PMID:9009796

  6. Probability and Relative Frequency

    NASA Astrophysics Data System (ADS)

    Drieschner, Michael

    2016-01-01

    The concept of probability seems to have been inexplicable since its invention in the seventeenth century. In its use in science, probability is closely related with relative frequency. So the task seems to be interpreting that relation. In this paper, we start with predicted relative frequency and show that its structure is the same as that of probability. I propose to call that the `prediction interpretation' of probability. The consequences of that definition are discussed. The "ladder"-structure of the probability calculus is analyzed. The expectation of the relative frequency is shown to be equal to the predicted relative frequency. Probability is shown to be the most general empirically testable prediction.

  7. Frequencies of solar oscillations

    NASA Technical Reports Server (NTRS)

    Libbrecht, K. G.; Woodard, M. F.; Kaufman, J. M.

    1990-01-01

    Solar oscillations have been observed at three different spatial scales at Big Bear Solar Observatory during 1986-1987 and, using three data sets, a new and more accurate table of solar oscillation frequencies has been compiled. The oscillations, which are presented as functions of radial order n and spherical harmonic degree l, are averages over azimuthal order and therefore approximate the normal mode frequencies of a nonrotating, spherically symmetric sun, near solar minimum. The table contains frequencies for most of the solar p and f modes with l between 0 and 1860, n between 0 and 26, and oscillation mode frequencies between 1.0 and 5.3.

  8. Nonlinear Frequency Compression

    PubMed Central

    Scollie, Susan; Glista, Danielle; Seelisch, Andreas

    2013-01-01

    Frequency lowering technologies offer an alternative amplification solution for severe to profound high frequency hearing losses. While frequency lowering technologies may improve audibility of high frequency sounds, the very nature of this processing can affect the perceived sound quality. This article reports the results from two studies that investigated the impact of a nonlinear frequency compression (NFC) algorithm on perceived sound quality. In the first study, the cutoff frequency and compression ratio parameters of the NFC algorithm were varied, and their effect on the speech quality was measured subjectively with 12 normal hearing adults, 12 normal hearing children, 13 hearing impaired adults, and 9 hearing impaired children. In the second study, 12 normal hearing and 8 hearing impaired adult listeners rated the quality of speech in quiet, speech in noise, and music after processing with a different set of NFC parameters. Results showed that the cutoff frequency parameter had more impact on sound quality ratings than the compression ratio, and that the hearing impaired adults were more tolerant to increased frequency compression than normal hearing adults. No statistically significant differences were found in the sound quality ratings of speech-in-noise and music stimuli processed through various NFC settings by hearing impaired listeners. These findings suggest that there may be an acceptable range of NFC settings for hearing impaired individuals where sound quality is not adversely affected. These results may assist an Audiologist in clinical NFC hearing aid fittings for achieving a balance between high frequency audibility and sound quality. PMID:23539261

  9. Stabilized radio frequency quadrupole

    DOEpatents

    Lancaster, Henry D.; Fugitt, Jock A.; Howard, Donald R.

    1984-01-01

    A long-vane stabilized radio frequency resonator for accelerating charged particles and including means defining a radio frequency resonator cavity, a plurality of long vanes mounted in the defining means for dividing the cavity into sections, and means interconnecting opposing ones of the plurality of vanes for stabilizing the resonator.

  10. Stabilized radio frequency quadrupole

    DOEpatents

    Lancaster, H.D.; Fugitt, J.A.; Howard, D.R.

    1984-12-25

    Disclosed is a long-vane stabilized radio frequency resonator for accelerating charged particles and including means defining a radio frequency resonator cavity, a plurality of long vanes mounted in the defining means for dividing the cavity into sections, and means interconnecting opposing ones of the plurality of vanes for stabilizing the resonator. 5 figs.

  11. Microfabricated ion frequency standard

    DOEpatents

    Schwindt, Peter; Biedermann, Grant; Blain, Matthew G.; Stick, Daniel L.; Serkland, Darwin K.; Olsson, III, Roy H.

    2010-12-28

    A microfabricated ion frequency standard (i.e. an ion clock) is disclosed with a permanently-sealed vacuum package containing a source of ytterbium (Yb) ions and an octupole ion trap. The source of Yb ions is a micro-hotplate which generates Yb atoms which are then ionized by a ultraviolet light-emitting diode or a field-emission electron source. The octupole ion trap, which confines the Yb ions, is formed from suspended electrodes on a number of stacked-up substrates. A microwave source excites a ground-state transition frequency of the Yb ions, with a frequency-doubled vertical-external-cavity laser (VECSEL) then exciting the Yb ions up to an excited state to produce fluorescent light which is used to tune the microwave source to the ground-state transition frequency, with the microwave source providing a precise frequency output for the ion clock.

  12. Precision frequency synthesizing sources with excellent time/frequency performances

    NASA Technical Reports Server (NTRS)

    Zhou, Liren; Lin, Hai

    1994-01-01

    Precision frequency synthesizing sources are needed in the time / frequency measuring system, atomic frequency standards, telemetry, communication, and radar systems. This kind of frequency synthesizing source possesses high frequency accuracy and excellent long term and short term frequency stability. Several precision frequency synthesizing sources developed by Beijing Institute of Radio Metrology and Measurement (BIRMM) which have been successfully applied to the time / frequency measuring system, atomic frequency standards system, and radar system are described. In addition, the working principle, implementation approach, and the main technical specifications of the frequency synthesizing sources are also given.

  13. Simple sweep frequency generator

    NASA Astrophysics Data System (ADS)

    Yegorov, I.

    1985-01-01

    A sweep frequency generator is described whose center frequency can be varied from 10 kHz to 50 MHz, with seven 1 to 3 and 3 to 10 scales covering the 10 kHz to 30 MHz range and one 3 to 5 scale for the 30 to 50 MHz range. It consists of a tunable pulse generator with output voltage attenuator, a diode mixer for calibration, and a sawtooth voltage generator as a source of frequency deviation. The pulse generator is a multivibrator with two emitter coupled transistors and two diodes in the collector circuit of one. The first diode extends the tuning range and increases the frequency deviation, the second diode provides the necessary base bias to the other transistor. The pulse repetition rate is modulated either directly by the sweep voltage of the calibrating oscilloscope, this voltage being applied to the base of the transistor with the two diodes in its collector circuit through an additional attenuator or a special emitter follower, or by the separate sawtooth voltage generator. The latter is a conventional two transistor multivibrator and produces signals at any constant frequency within the 40 to 60 Hz range. The mixer receives unmodulated signals from a reference frequency source and produces different frequency signals which are sent through an RCR-filter to a calibrating oscilloscope.

  14. Frequency discriminating laser

    SciTech Connect

    Thomas, M.D.

    1987-10-20

    A laser is described for discriminating between a higher gain transition and a lower gain transition to permit the laser to lase at the lower gain transition. It consists of: a laser cavity, including more than two mirrors each of which is highly transmissive at the frequency of the higher gain transition, one of which is partially reflective at the frequency of the lower gain transition, and all but the one of which are highly reflective at the frequency of the lower gain transition; an active laser medium disposed within the cavity; and means for pumping the active laser medium.

  15. Optical Frequency Domain Imaging

    NASA Astrophysics Data System (ADS)

    Bouma, Brett E.; Tearney, Guillermo J.; Vakoc, Benjamin; Yun, Seok Hyun

    In this chapter, we discuss a frequency-domain approach, optical frequency-domain imaging (OFDI), which is based on optical frequency-domain reflectometry and uses a wavelength-swept laser and standard single-element photodetectors. The chapter begins with an overview of the fundamental aspects of the technology, including the detected signal, sensitivity, depth range, and resolution, and then goes on to discuss specific component technologies including the light source, interferometer and acquisition electronics, and image processing. The final section of the chapter provides a brief glimpse at some of the biomedical applications that most directly take advantage of the improved speed and sensitivity of OFDI.

  16. Frequency stabilized laser

    NASA Astrophysics Data System (ADS)

    Mongeon, R. J.; Henschke, R. W.

    1984-08-01

    The document describes a frequency control system for a laser for compensating for thermally-induced laser resonator length changes. The frequency control loop comprises a frequency reference for producing an error signal and electrical means to move a length-controlling transducer in response thereto. The transducer has one of the laser mirrors attached thereto. The effective travel of the transducer is multiplied severalfold by circuitry for sensing when the transducer is running out of extension and in response thereto rapidly moving the transducer and its attached mirror toward its midrange position.

  17. A beat frequency buncher

    SciTech Connect

    Storm, D.W.; Corcoran, D.T.; Harper, G.C.

    1995-09-01

    A superconducting high energy buncher operating at 13/12 times the linac frequency has been built and installed, to combine with the low energy buncher operating at 1/12 the linac frequency. The system is synchronized so the linac and high energy buncher beat frequency remains in phase with the low energy buncher. On linac cycles not corresponding to a primary bunch, the high energy buncher bunches residual beam away from the linac longitudinal acceptance rather than into it. The resonator for the new high energy buncher was constructed by shortening an existing low-{beta} resonator.

  18. Histograms and Frequency Density.

    ERIC Educational Resources Information Center

    Micromath, 2003

    2003-01-01

    Introduces exercises on histograms and frequency density. Guides pupils to Discovering Important Statistical Concepts Using Spreadsheets (DISCUSS), created at the University of Coventry. Includes curriculum points, teaching tips, activities, and internet address (http://www.coventry.ac.uk/discuss/). (KHR)

  19. Laser Frequency and Time

    NASA Astrophysics Data System (ADS)

    Hänsch, Theodor W.

    2003-04-01

    The following two contributions in this volume are highlighting some remarkable recent developments at the interface between precision laser spectroscopy and ultrafast laser physics. After decades of struggle, we have finally found a practical method for measuring the frequency of light with extreme precision [1]. Femtosecond laser optical frequency comb synthesizers are opening exciting new perspectives for atomic spectroscopy and they can provide the clockwork for optical atomic clocks that will eventually far surpass the accuracy of the best microwave cesium clocks. J. C. Bergquist et al. [2] are reporting on a first optical atomic clock at NIST based on a single trapped Hg+ ion. The contribution by Jun Ye et al. [3] is illustrating the wealth of new opportunities for femtosecond laser frequency combs in the frequency and time domain.

  20. Acoustic emission frequency discrimination

    NASA Technical Reports Server (NTRS)

    Sugg, Frank E. (Inventor); Graham, Lloyd J. (Inventor)

    1988-01-01

    In acoustic emission nondestructive testing, broadband frequency noise is distinguished from narrow banded acoustic emission signals, since the latter are valid events indicative of structural flaws in the material being examined. This is accomplished by separating out those signals which contain frequency components both within and beyond (either above or below) the range of valid acoustic emission events. Application to acoustic emission monitoring during nondestructive bond verification and proof loading of undensified tiles on the Space Shuttle Orbiter is considered.

  1. On letter frequency effects.

    PubMed

    New, Boris; Grainger, Jonathan

    2011-10-01

    In four experiments we examined whether the frequency of occurrence of letters affects performance in the alphabetic decision task (speeded letter vs. pseudo-letter classification). Experiments 1A and 1B tested isolated letters and pseudo-letters presented at fixation, and Experiments 2A and 2B tested the same stimuli inserted at the 1st, 3rd, or 5th position in a string of Xs. Significant negative correlations between letter frequency and response times to letter targets were found in all experiments. The correlations were found to be stronger for token frequency counts compared with both type frequency and frequency rank, stronger for frequency counts based on a book corpus compared with film subtitles, and stronger for measures counting occurrences as the first letter of words compared with inner letters and final letters. Correlations for letters presented in strings of Xs were found to depend on letter case and position-in-string. The results are in favor of models of word recognition that implement case-specific and position-specific letter representations. PMID:21855049

  2. Frequency Standards and Metrology

    NASA Astrophysics Data System (ADS)

    Maleki, Lute

    2009-04-01

    Preface / Lute Maleki -- Symposium history / Jacques Vanier -- Symposium photos -- pt. I. Fundamental physics. Variation of fundamental constants from the big bang to atomic clocks: theory and observations (Invited) / V. V. Flambaum and J. C. Berengut. Alpha-dot or not: comparison of two single atom optical clocks (Invited) / T. Rosenband ... [et al.]. Variation of the fine-structure constant and laser cooling of atomic dysprosium (Invited) / N. A. Leefer ... [et al.]. Measurement of short range forces using cold atoms (Invited) / F. Pereira Dos Santos ... [et al.]. Atom interferometry experiments in fundamental physics (Invited) / S. W. Chiow ... [et al.]. Space science applications of frequency standards and metrology (Invited) / M. Tinto -- pt. II. Frequency & metrology. Quantum metrology with lattice-confined ultracold Sr atoms (Invited) / A. D. Ludlow ... [et al.]. LNE-SYRTE clock ensemble: new [symbol]Rb hyperfine frequency measurement - spectroscopy of [symbol]Hg optical clock transition (Invited) / M. Petersen ... [et al.]. Precise measurements of S-wave scattering phase shifts with a juggling atomic clock (Invited) / S. Gensemer ... [et al.]. Absolute frequency measurement of the [symbol] clock transition (Invited) / M. Chwalla ... [et al.]. The semiclassical stochastic-field/atom interaction problem (Invited) / J. Camparo. Phase and frequency noise metrology (Invited) / E. Rubiola ... [et al.]. Optical spectroscopy of atomic hydrogen for an improved determination of the Rydberg constant / J. L. Flowers ... [et al.] -- pt. III. Clock applications in space. Recent progress on the ACES mission (Invited) / L. Cacciapuoti and C. Salomon. The SAGAS mission (Invited) / P. Wolf. Small mercury microwave ion clock for navigation and radioScience (Invited) / J. D. Prestage ... [et al.]. Astro-comb: revolutionizing precision spectroscopy in astrophysics (Invited) / C. E. Kramer ... [et al.]. High frequency very long baseline interferometry: frequency standards and

  3. Monolithic THz Frequency Multipliers

    NASA Technical Reports Server (NTRS)

    Erickson, N. R.; Narayanan, G.; Grosslein, R. M.; Martin, S.; Mehdi, I.; Smith, P.; Coulomb, M.; DeMartinez, G.

    2001-01-01

    Frequency multipliers are required as local oscillator sources for frequencies up to 2.7 THz for FIRST and airborne applications. Multipliers at these frequencies have not previously been demonstrated, and the object of this work was to show whether such circuits are really practical. A practical circuit is one which not only performs as well as is required, but also can be replicated in a time that is feasible. As the frequency of circuits is increased, the difficulties in fabrication and assembly increase rapidly. Building all of the circuit on GaAs as a monolithic circuit is highly desirable to minimize the complexity of assembly, but at the highest frequencies, even a complete monolithic circuit is extremely small, and presents serious handling difficulty. This is compounded by the requirement for a very thin substrate. Assembly can become very difficult because of handling problems and critical placement. It is very desirable to make the chip big enough to that it can be seen without magnification, and strong enough that it may be picked up with tweezers. Machined blocks to house the chips present an additional challenge. Blocks with complex features are very expensive, and these also imply very critical assembly of the parts. It would be much better if the features in the block were as simple as possible and non-critical to the function of the chip. In particular, grounding and other electrical interfaces should be done in a manner that is highly reproducible.

  4. Frequency Standards and Metrology

    NASA Astrophysics Data System (ADS)

    Maleki, Lute

    2009-04-01

    Preface / Lute Maleki -- Symposium history / Jacques Vanier -- Symposium photos -- pt. I. Fundamental physics. Variation of fundamental constants from the big bang to atomic clocks: theory and observations (Invited) / V. V. Flambaum and J. C. Berengut. Alpha-dot or not: comparison of two single atom optical clocks (Invited) / T. Rosenband ... [et al.]. Variation of the fine-structure constant and laser cooling of atomic dysprosium (Invited) / N. A. Leefer ... [et al.]. Measurement of short range forces using cold atoms (Invited) / F. Pereira Dos Santos ... [et al.]. Atom interferometry experiments in fundamental physics (Invited) / S. W. Chiow ... [et al.]. Space science applications of frequency standards and metrology (Invited) / M. Tinto -- pt. II. Frequency & metrology. Quantum metrology with lattice-confined ultracold Sr atoms (Invited) / A. D. Ludlow ... [et al.]. LNE-SYRTE clock ensemble: new [symbol]Rb hyperfine frequency measurement - spectroscopy of [symbol]Hg optical clock transition (Invited) / M. Petersen ... [et al.]. Precise measurements of S-wave scattering phase shifts with a juggling atomic clock (Invited) / S. Gensemer ... [et al.]. Absolute frequency measurement of the [symbol] clock transition (Invited) / M. Chwalla ... [et al.]. The semiclassical stochastic-field/atom interaction problem (Invited) / J. Camparo. Phase and frequency noise metrology (Invited) / E. Rubiola ... [et al.]. Optical spectroscopy of atomic hydrogen for an improved determination of the Rydberg constant / J. L. Flowers ... [et al.] -- pt. III. Clock applications in space. Recent progress on the ACES mission (Invited) / L. Cacciapuoti and C. Salomon. The SAGAS mission (Invited) / P. Wolf. Small mercury microwave ion clock for navigation and radioScience (Invited) / J. D. Prestage ... [et al.]. Astro-comb: revolutionizing precision spectroscopy in astrophysics (Invited) / C. E. Kramer ... [et al.]. High frequency very long baseline interferometry: frequency standards and

  5. Single frequency multitransmitter telemetry

    NASA Technical Reports Server (NTRS)

    Carreno, Victor A. (Inventor)

    1986-01-01

    The invention relates to a single frequency multitransmitter telemetry system that will deliver a substantial amount of data at low cost. The invention consists essentially of a plurality of sensor transmitter units at different locations, with individual signal conditioning and logic, which send sampled data signals to a single receiver. The transmitters operate independently on the same frequency in a frequency shift keying modulation system and are not synchronized to the receiver. The problem of reception of data from more than one transmitter simultaneously is solved by discarding the data - when there is overlap of data from two or more transmitters, the data is discarded and when there is no overlap the data is retained. The invention utilizes a unique overlap detection technique to determine if data should be retained or discarded. When data is received from a transmitter, it goes into a shift register.

  6. Low Frequency Sky Surveys

    NASA Astrophysics Data System (ADS)

    Lubin, Philip M.

    2015-08-01

    We propose to survey the sky from 10-100 GHz covering greater than 50% of the sky in intensity and polarizatiton. This will allow us to mep out the synchrotron and free - free background as well as the spinning dust component to sufficient sensitivity to allow detailed modeling and removal of the galactic foregrounds allowing for deeper polarization surveys searching for signatures of inflation. While most measurements have concentrated on the region above 100 GHz this reggion is more complex in dust contmination that originally thought. Dust is best measured at high frequencies but the atmosphere greatly hinders extremely deep dust surveys due to water vapor. Surveys ar low frequency will be complimentary to the higher frequency measurements.

  7. Frequency conversion system

    NASA Technical Reports Server (NTRS)

    Sanders, Steven (Inventor); Lang, Robert J. (Inventor)

    2001-01-01

    Laser diode pumped mid-IR wavelength sources include at least one high power, near-IR wavelength, injection and/or sources wherein one or both of such sources may be tunable providing a pump wave output beam to a quasi-phase matched (QPM) nonlinear frequency mixing (NFM) device. The NFM device may be a difference frequency mixing (DFM) device or an optical parametric oscillation (OPO) device. Wavelength tuning of at least one of the sources advantageously provides the ability for optimizing pump or injection wavelengths to match the QPM properties of the NFM device enabling a broad range of mid-IR wavelength selectivity. Also, pump powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Raman/Brillouin amplifier or oscillator between the high power source and the NFM device. Further, polarization conversion using Raman or Brillouin wavelength shifting is provided to optimize frequency conversion efficiency in the NFM device.

  8. Hg(+) Frequency Standards

    NASA Technical Reports Server (NTRS)

    Prestage, John D.; Tjoelker, Robert L.; Maleki, Lute

    2000-01-01

    In this paper we review the development of Hg(+) microwave frequency standards for use in high reliability and continuous operation applications. In recent work we have demonstrated short-term frequency stability of 3 x 10(exp -14)/nu(sub tau) when a cryogenic oscillator of stability 2-3 x 10(exp 15) was used a the local oscillator. The trapped ion frequency standard employs a Hg-202 discharge lamp to optically pump the trapped Hg(+)-199 clock ions and a helium buffer gas to cool the ions to near room temperature. We describe a small Hg(+) ion trap based frequency standard with an extended linear ion trap (LITE) architecture which separates the optical state selection region from the clock resonance region. This separation allows the use of novel trap configurations in the resonance region since no optical pumping is carried out there. A method for measuring the size of an ion cloud inside a linear trap with a 12-rod trap is currently being investigated. At approx. 10(exp -12), the 2nd order Doppler shift for trapped mercury ion frequency standards is one of the largest frequency offsets and its measurement to the 1% level would represent an advance in insuring the very long-term stability of these standards to the 10(exp -14) or better level. Finally, we describe atomic clock comparison experiments that can probe for a time variation of the fine structure constant, alpha = e(exp 2)/2(pi)hc, at the level of 10(exp -20)/year as predicted in some Grand Unified String Theories.

  9. Frequency division multiplex technique

    NASA Technical Reports Server (NTRS)

    Brey, H. (Inventor)

    1973-01-01

    A system for monitoring a plurality of condition responsive devices is described. It consists of a master control station and a remote station. The master control station is capable of transmitting command signals which includes a parity signal to a remote station which transmits the signals back to the command station so that such can be compared with the original signals in order to determine if there are any transmission errors. The system utilizes frequency sources which are 1.21 multiples of each other so that no linear combination of any harmonics will interfere with another frequency.

  10. Frequency Tunable Wire Lasers

    NASA Technical Reports Server (NTRS)

    Hu, Qing (Inventor)

    2013-01-01

    The present invention provides frequency tunable solid-state radiation-generating devices, such as lasers and amplifiers, whose active medium has a size in at least one transverse dimension (e.g., its width) that is much smaller than the wavelength of radiation generated and/or amplified within the active medium. In such devices, a fraction of radiation travels as an evanescent propagating mode outside the active medium. It has been discovered that in such devices the radiation frequency can be tuned by the interaction of a tuning mechanism with the propagating evanescent mode.

  11. Dual frequency optical cavity

    DOEpatents

    George, E.V.; Schipper, J.F.

    Method and apparatus for generating two distinct laser frequencies in an optical cavity, using a T configuration laser cavity and means for intermittently increasing or decreasing the index of refraction n of an associated transmission medium in one arm of the optical cavity to enhance laser action in one arm or the second arm of the cavity.

  12. Dual frequency optical cavity

    DOEpatents

    George, E. Victor; Schipper, John F.

    1985-01-01

    Method and apparatus for generating two distinct laser frequencies in an optical cavity, using a "T" configuration laser cavity and means for intermittently increasing or decreasing the index of refraction n of an associated transmission medium in one arm of the optical cavity to enhance laser action in one arm or the second arm of the cavity.

  13. The Frequency Spectrum Radio.

    ERIC Educational Resources Information Center

    Howkins, John, Ed.

    1979-01-01

    This journal issue focuses on the frequency spectrum used in radio communication and on the World Administrative Radio Conference, sponsored by the International Telecommunication Union, held in Geneva, Switzerland, in the fall of 1979. Articles describe the World Administrative Radio Conference as the most important radio communication conference…

  14. Frequency of orthodontic extraction

    PubMed Central

    Dardengo, Camila de S.; Fernandes, Luciana Q. P.; Capelli, Jonas

    2016-01-01

    Introduction: The option of dental extraction for orthodontic purposes has been debated for more than 100 years, including periods when it was widely used in treatment, including the present, during which other methods are used to avoid dental extractions. The objective was to analyze the frequency of tooth extraction treatment performed between 1980 and 2011 at the Orthodontic Clinic of Universidade Estadual do Rio de Janeiro (UERJ). Material and Methods: The clinical records of 1484 patients undergoing orthodontic treatment were evaluated. The frequency of extractions was evaluated with regard to sex, Angle's classification, the different combinations of extractions and the period when orthodontic treatment began. Chi-square test was used to determine correlations between variables, while the chi-square test for trends was used to assess the frequency of extractions over the years. Results: There was a reduction of approximately 20% in the frequency of cases treated with tooth extraction over the last 32 years. The most frequently extracted teeth were first premolars. Patients with Class I malocclusion showed fewer extractions, while Class II patients underwent a higher number of extraction treatment. There were no statistically significant differences with regard to sex. Conclusion: New features introduced into the orthodontic clinic and new esthetic concepts contributed to reducing the number of cases treated with dental extractions. However, dental extractions for orthodontic purposes are still well indicated in certain cases. PMID:27007762

  15. Optical frequency comb spectroscopy.

    PubMed

    Foltynowicz, A; Masłowski, P; Ban, T; Adler, F; Cossel, K C; Briles, T C; Ye, J

    2011-01-01

    Optical frequency combs offer enormous potential in the detection and control of atoms and molecules by combining their vast spectral coverage with the extremely high spectral resolution of each individual comb component. Sensitive and multiplexed trace gas detection via cavity-enhanced direct frequency comb spectroscopy has been demonstrated for various molecules and applications; however, previous demonstrations have been confined to the visible and near-infrared wavelength range. Future spectroscopic capabilities are created by developing comb sources and spectrometers for the deep ultraviolet and mid-infrared spectral regions. Here we present a broadband high resolution mid-infrared frequency comb-based Fourier transform spectrometer operating in the important molecular fingerprint spectral region of 2100-3600 cm(-1) (2.8-4.8 microm). The spectrometer, employing a multipass cell, allows simultaneous acquisition of broadband, high resolution spectra (down to 0.0035 cm(-1) of many molecular species at concentrations in the part-per-billion range in less than 1 min acquisition time. The system enables precise measurements of concentration even in gas mixtures that exhibit continuous absorption bands. The current sensitivity, 2 x 10(-8) cm(-1) Hz-1/2 per spectral element, is expected to improve by two orders of magnitude with an external enhancement cavity. We have demonstrated this sensitivity increase by combining cavity-enhanced frequency comb spectroscopy with a scanning Fourier transform spectrometer in the near-infrared region and achieving a sensitivity of 4.7 x 10(-10) cm(-1) Hz(-1/2). A cavity-enhanced mid-infrared comb spectrometer will provide a near real-time, high sensitivity, high resolution, precisely frequency calibrated, broad bandwidth system for many applications. PMID:22457942

  16. Coarse frequency comb interferometry

    NASA Astrophysics Data System (ADS)

    Schwider, J.

    2008-08-01

    Real wedge interferometers of the Fizeau-type do not allow for fringes in case of a spectral broad band source - or in short: for white light fringes. Here, the use of a suitable frequency comb source will help to overcome this limitation on the one hand and on the other will offer the capability for enhanced phase sensitivity in high precision measurements of surface deviations. Frequency combs can be produced either by using a pulse train from a fs-laser or by passive filtering of the light emitted by a broad band source as a superlum-diode or a fs-laser. The frequency comb produced by a common fs-laser is extremely fine, i.e., the frequency difference of consecutive peaks is very small or the distance of consecutive pulses of the pulse train might be of the order of 1m. Therefore, the coarse pulse train produced by passive filtering of a broad band source is better adapted to the needs of surface testing interferometers. White light fringes are either applied for the profiling of discontinuous surfaces and/or can serve as an indication for the correct choice of multiplication factors in superposition interferometry. During the last decennium it became more and more clear that spatially incoherent sources provide better measuring accuracy in surface measurements due to the reduced influence of dust diffraction patterns. The advantage of laser illumination can nevertheless be maintained if the laser light is made spatially incoherent through moving scatterers in the light path. Here, we will discuss the application of spatially incoherent broad band light frequency filtered through a Fabry-Perot filter. The main applications are in the following fields: (1) surface profiling applications using two-beam Fizeau interferometers, (2) selection of single cavities out of a series of interlaced cavities, and (3) sensitivity enhancement for multi-beam interferometers for planeness or sphericity measurements. Some of the discussed possibilities will be experimentally

  17. Deep frequency modulation interferometry.

    PubMed

    Gerberding, Oliver

    2015-06-01

    Laser interferometry with pm/Hz precision and multi-fringe dynamic range at low frequencies is a core technology to measure the motion of various objects (test masses) in space and ground based experiments for gravitational wave detection and geodesy. Even though available interferometer schemes are well understood, their construction remains complex, often involving, for example, the need to build quasi-monolithic optical benches with dozens of components. In recent years techniques have been investigated that aim to reduce this complexity by combining phase modulation techniques with sophisticated digital readout algorithms. This article presents a new scheme that uses strong laser frequency modulations in combination with the deep phase modulation readout algorithm to construct simpler and easily scalable interferometers. PMID:26072834

  18. High frequency reference electrode

    DOEpatents

    Kronberg, J.W.

    1994-05-31

    A high frequency reference electrode for electrochemical experiments comprises a mercury-calomel or silver-silver chloride reference electrode with a layer of platinum around it and a layer of a chemically and electrically resistant material such as TEFLON around the platinum covering all but a small ring or halo' at the tip of the reference electrode, adjacent to the active portion of the reference electrode. The voltage output of the platinum layer, which serves as a redox electrode, and that of the reference electrode are coupled by a capacitor or a set of capacitors and the coupled output transmitted to a standard laboratory potentiostat. The platinum may be applied by thermal decomposition to the surface of the reference electrode. The electrode provides superior high-frequency response over conventional electrodes. 4 figs.

  19. Extended frequency turbofan model

    NASA Technical Reports Server (NTRS)

    Mason, J. R.; Park, J. W.; Jaekel, R. F.

    1980-01-01

    The fan model was developed using two dimensional modeling techniques to add dynamic radial coupling between the core stream and the bypass stream of the fan. When incorporated into a complete TF-30 engine simulation, the fan model greatly improved compression system frequency response to planar inlet pressure disturbances up to 100 Hz. The improved simulation also matched engine stability limits at 15 Hz, whereas the one dimensional fan model required twice the inlet pressure amplitude to stall the simulation. With verification of the two dimensional fan model, this program formulated a high frequency F-100(3) engine simulation using row by row compression system characteristics. In addition to the F-100(3) remote splitter fan, the program modified the model fan characteristics to simulate a proximate splitter version of the F-100(3) engine.

  20. [High frequency ultrasound].

    PubMed

    Sattler, E

    2015-07-01

    Diagnostic ultrasound has become a standard procedure in clinical dermatology. Devices with intermediate high frequencies of 7.5-15 MHz are used in dermato-oncology for the staging and postoperative care of skin tumor patients and in angiology for improved vessel diagnostics. In contrast, the high frequency ultrasound systems with 20-100 MHz probes offer a much higher resolution, yet with a lower penetration depth of about 1 cm. The main indications are the preoperative measurements of tumor thickness in malignant melanoma and other skin tumors and the assessment of inflammatory and soft tissue diseases, offering information on the course of these dermatoses and allowing therapy monitoring. This article gives an overview on technical principles, devices, mode of examination, influencing factors, interpretation of the images, indications but also limitations of this technique. PMID:25636803

  1. High frequency reference electrode

    DOEpatents

    Kronberg, James W.

    1994-01-01

    A high frequency reference electrode for electrochemical experiments comprises a mercury-calomel or silver-silver chloride reference electrode with a layer of platinum around it and a layer of a chemically and electrically resistant material such as TEFLON around the platinum covering all but a small ring or "halo" at the tip of the reference electrode, adjacent to the active portion of the reference electrode. The voltage output of the platinum layer, which serves as a redox electrode, and that of the reference electrode are coupled by a capacitor or a set of capacitors and the coupled output transmitted to a standard laboratory potentiostat. The platinum may be applied by thermal decomposition to the surface of the reference electrode. The electrode provides superior high-frequency response over conventional electrodes.

  2. Multiwire thermocouples: Frequency response

    NASA Technical Reports Server (NTRS)

    Forney, L. J.; Fralick, G. C.

    1994-01-01

    Experimental measurements are made with a novel two wire thermocouple. Signals from two wires of unequal diameters are recorded from the thermocouple suspended in constant flow with a periodic temperature fluctuation. It is demonstrated that the reconstructed signal from the two wire thermocouple requires no compensation for omega less than or equal to 2 omega(sub 1) where omega is the natural frequency of the smaller wire. A compensation factor is recommended for larger frequencies omega greater than 2 omega(sub 1). Theory and experimental measurements are compared with a novel three wire thermocouple. Signals from three wires of unequal diameters are recorded from the thermocouple suspended in constant flow with a periodic temperature fluctuation. It is demonstrated that the reconstructed signal from the three wire thermocouple requires no compensation for omega less than or equal to 5 omega(sub 1) where omega (sub 1) is the natural frequency of the smaller wire. The latter result represents a significant improvement compared to previous work with two wire thermocouples. A correction factor has also been derived to account for wires of arbitrary diameter. Measurements are recorded for multiwire thermocouples consisting of either two or three wires of unequal diameters. Signals from the multiwire probe are recorded for a reversing gas flow with a periodic temperature fluctuation. It is demonstrated that the reconstructed signal from the multiwire thermocouple requires no compensation provided omega/omega(sub 1) is less than 2.3 for two wires or omega/omega(sub 1) is less than 3.6 for three wires where omega(sub 1) is the natural frequency of the smaller wire based on the maximum gas velocity. The latter results were possible provided Fourier transformed data were used and knowledge of the gas velocity is available.

  3. Rapid frequency scan EPR.

    PubMed

    Tseitlin, Mark; Rinard, George A; Quine, Richard W; Eaton, Sandra S; Eaton, Gareth R

    2011-08-01

    In rapid frequency scan EPR with triangular scans, sufficient time must be allowed to insure that the magnetization in the x, y plane decays to baseline at the end of the scan, which typically is about 5T(2) after the spins are excited. To permit relaxation of signals excited toward the extremes of the scan the total scan time required may be much longer than 5T(2). However, with periodic, saw-tooth excitation, the slow-scan EPR spectrum can be recovered by Fourier deconvolution of data recorded with a total scan period of 5T(2), even if some spins are excited later in the scan. This scan time is similar to polyphase excitation methods. The peak power required for either polyphase excitation or rapid frequency scans is substantially smaller than for pulsed EPR. The use of an arbitrary waveform generator (AWG) and cross loop resonator facilitated implementation of the rapid frequency scan experiments reported here. The use of constant continuous low B(1), periodic excitation waveform, and constant external magnetic field is similar to polyphase excitation, but could be implemented without the AWG that is required for polyphase excitation. PMID:21664848

  4. Rapid Frequency Scan EPR

    PubMed Central

    Tseitlin, Mark; Rinard, George A.; Quine, Richard W.; Eaton, Sandra S.; Eaton, Gareth R.

    2011-01-01

    In rapid frequency scan EPR with triangular scans, sufficient time must be allowed to insure that the magnetization in the x,y plane decays to baseline at the end of the scan, which typically is about 5 T2 after the spins are excited. To permit relaxation of signals excited toward the extremes of the scan the total scan time required may be much longer than 5 T2. However, with periodic, saw-tooth excitation, the slow-scan EPR spectrum can be recovered by Fourier deconvolution of data recorded with a total scan period of 5 T2, even if some spins are excited later in the scan. This scan time is similar to polyphase excitation methods. The peak power required for either polyphase excitation or rapid frequency scans is substantially smaller than for pulsed EPR. The use of an arbitrary waveform generator (AWG) and cross loop resonator facilitated implementation of the rapid frequency scan experiments reported here. The use of constant continuous low B1, periodic excitation waveform, and constant external magnetic field is similar to polyphase excitation, but could be implemented without the AWG that is required for polyphase excitation. PMID:21664848

  5. Drought Frequency Index

    NASA Astrophysics Data System (ADS)

    Gonzalez, J.; Valdes, J. B.

    2003-04-01

    Droughts are related with prolonged time periods during moisture is significantly below normal situation. Drought indexes try to scale the main drought features based on similar definitions. The Standard Precipitation Index (SPI) is a well-known index, which for a given aggregation-time measures the deviation from the normality of the precipitation. One of the SPI weak points in the representation of drought phenomenon is that drought duration should be analyzed by using different aggregation-times. In this work, a new index is presented, which simultaneously characterize droughts based on the deviation from the normal precipitation regime and the drought persistence, both from the statistical point of view. The new index does not require aggregation at different time-lengths. Instead droughts are treated as multivariate events, whose dimensionality depends on the duration. Probabilistic events with different dimensionalities are compared on a common dimension of interest. In this case the dimension chosen is the mean frequency of recurrence. The derived index, named Drought Frequency Index (DFI) may be used to characterize historical droughts or current situation. It can be apply not only over precipitation but also over flows or other hydroclimatic variables. The new index was applied to several places in USA and Spain both for precipitation and flow historical sequences, and compared with SPI. The DFI allows the representation of the main drought characteristics in a single value, based on the stochastic feature of the phenomenon, and scaled on the mean frequency of recurrence.

  6. Active frequency selective surfaces

    NASA Astrophysics Data System (ADS)

    Buchwald, Walter R.; Hendrickson, Joshua; Cleary, Justin W.; Guo, Junpeng

    2013-05-01

    Split ring resonator arrays are investigated for use as active elements for the realization of voltage controllable frequency selective surfaces. Finite difference time domain simulations suggest the absorptive and reflective properties of such surfaces can be externally controlled through modifications of the split ring resonator gap impedance. In this work, such voltage-controlled resonance tuning is obtained through the addition of an appropriately designed high electron mobility transistor positioned across the split ring resonator gap. It is shown that a 0.5μm gate length high electron mobility transistor allows voltage controllable switching between the two resonant conditions associated with a split ring resonator and that of a closed loop geometry when the surface is illuminated with THz radiation. Partial switching between these two resonant conditions is observed at larger gate lengths. Such active frequency selective surfaces are proposed, for example, for use as modulators in THz detection schemes and as RF filters in radar applications when scaled to operate at GHz frequencies.

  7. Fiber optic frequency transfer link

    NASA Technical Reports Server (NTRS)

    Primas, Lori E. (Inventor); Sydnor, Richard L. (Inventor); Lutes, George F. (Inventor)

    1991-01-01

    A reference frequency distribution system is disclosed for transmitting a reference frequency from a reference unit to a remote unit while keeping the reference frequency at the reference unit and the remote unit in phase. A fiber optic cable connects the reference unit to the remote unit. A frequency source at the reference unit produces a reference frequency having an adjustable phase. A fiber optic transmitter at the reference unit modulates a light beam with the reference frequency and transmits the light beam into the fiber optic cable. A 50/50 reflector at the remote unit reflects a first portion of the light beam from the reference unit back into the fiber optic cable to the reference unit. A first fiber optic receiver disposed at the remote unit receives a second portion of the light beam and demodulates the reference frequency to be used at the remote unit. A second fiber optic receiver disposed at the reference unit receives the first portion of the light beam and demodulates a reference frequency component. A phase conjugator is connected to the frequency source for comparing the phase of the reference frequency component to the phase of the reference frequency modulating the light beam being transmitted from the reference unit to maintain a conjugate (anti-symmetric) relationship between the reference frequency component and the reference frequency modulating the light beam where virtually no phase difference exists between the phase of the reference frequency component and the phase of the reference frequency modulating the light beam.

  8. Behaviour of radiocaesium in coastal rivers of the Fukushima Prefecture (Japan) during conditions of low flow and low turbidity--Insight on the possible role of small particles and detrital organic compounds.

    PubMed

    Eyrolle-Boyer, Frédérique; Boyer, Patrick; Garcia-Sanchez, Laurent; Métivier, Jean-Michel; Onda, Yuichi; De Vismes, Anne; Cagnat, Xavier; Boulet, Béatrice; Cossonnet, Catherine

    2016-01-01

    To investigate riverine transfers from contaminated soils of the Fukushima Prefecture in Japan to the marine environment, suspended sediments, filtered water, sediments and detrital organic macro debris deposited onto river beds were collected in November 2013 within small coastal rivers during conditions of low flow rates and low turbidity. River waters were directly filtered on the field and high efficiency well-type Ge detectors were used to analyse radiocaesium concentrations in very small quantities of suspended particles and filtered water (a few mg to a few g). For such base-flow conditions, our results show that the watersheds studied present similar hydro-sedimentary behaviours at their outlets and that the exports of dissolved and particulate radiocaesium are comparable. Moreover, the contribution of these rivers to the instantaneous export of radiocaesium to the ocean is similar to that of the Abukuma River. Our preliminary results indicate that, in the estuaries, radiocaesium concentrations in suspended sediments would be reduced by more than 80%, while radiocaesium concentration in filtered waters would be maintained. Significant correlations between radiocaesium concentrations and radiocaesium inventories in the soils of the catchments indicate that there was at that time little intra and inter-watershed variability in the transfer processes of radiocaesium from lands to rivers at this regional scale. The apparent liquid-solid partition coefficient (KD) values acquired for the lowest loads/finest particles complement the values acquired by using sediment traps and highlight the strong capacity of the smallest particles to transfer radiocaesium. Finally, but not least, our observations suggest that there could be a significant transfer of highly contaminated detrital biomass from forest litter to the downstream rivers in a rather conservative way. PMID:26588202

  9. Evaluation of interactions between metal ions and nonionic surfactants in high-concentration HCl using low-pressure high-performance liquid chromatography with low-flow-resistance polystyrene-based monolithic column.

    PubMed

    Hirano, Tomohiko; Kitagawa, Shinya; Ohtani, Hajime; Kinoshita, Takehiko; Ishigaki, Yuzo; Shibata, Nobuyuki; Nii, Susumu

    2013-10-01

    A method for evaluating the interactions between metal ions and nonionic surfactants in aqueous solutions containing high-concentration HCl, using gas pressure-driven low-pressure high-performance liquid chromatography (LP-HPLC) as a highly acid-resistant HPLC system, was developed. To construct the LP-HPLC for this purpose, poly(styrene-co-divinylbenzene)-based low-flow-resistance monolithic columns tolerant to highly acidic conditions were prepared using low-conversion thermal polymerization. Thermal polymerization at 65 °C for 1.5 h (monomer conversions, 33% for styrene and 59% for divinylbenzene) allowed preparation of a column with both high separation efficiency (around 60,000 plates m(-1) for alkylbenzenes) and a quite low back pressure of 0.14 MPa at a linear flow rate of 1 mm s(-1) (2.8 × 10(-13) m(2) in permeability). The base column prepared under the above conditions was coated with a nonionic surfactant, polyoxyethylene nonylphenyl ether (PONPE, average oxyethylene unit numbers (n) = 3, 7.5, 15, and 20), and used for evaluation of the interactions between PONPEs and metal ions in 6 M HCl. The interactions between PONPEs and Au(III), Ga(III), Fe(III), Zn(II), and Cu(II) were successfully evaluated using both breakthrough and chromatographic methods. Furthermore, a study of the effect of the polyoxyethylene (POE) chain length revealed that the use of PONPE with the longer POE moiety enhanced the magnitude of the interaction together with the increase in the amount of oxyethylene (OE) units coated on the monolith. Moreover, the interactions of metal ions with a single OE unit were almost constant in the range of n = 7.5-20, whereas the suppression of the interaction between Au(III) with the shortest PONPE chain (n = 3) was also observed. PMID:23884474

  10. Radar frequency radiation

    NASA Astrophysics Data System (ADS)

    Malowicki, E.

    1981-11-01

    A method is presented for the determination of radar frequency radiation power densities that the PAVE PAWS radar system could produce in its air and ground environment. The effort was prompted by the concern of the people in the vicinity of OTIS AFB MA and BEALE AFB CA about the possible radar frequency radiation hazard of the PAVE PAWS radar. The method is based on the following main assumptions that: (a) the total field can be computed as the vector summation of the individual fields due to each antenna element; (b) the individual field can be calculated using distances for which the field point is in the far field of the antenna element. An RFR computer program was coded for the RADC HE 6180 digital computer and exercised to calculate the radiation levels in the air and ground space for the present baseline and the possible Six DB and 10 DB growth systems of the PAVE PAWS radar system at OTIS AFB MA. The average radiation levels due to the surveillance fence were computed for three regions: in the air space in front of the radar, at the radar hazard fence at OTIS AFB MA and at representative ground points in the OTIS AFB vicinity. It was concluded that the radar frequency radiation of PAVE PAWS does not present a hazard to personnel provided there is no entry to the air hazard zone or to the area within the hazard fence. The method developed offers a cost effective way to determine radiation levels from a phased array radar especially in the near field and transition regions.

  11. Resonance frequency analysis.

    PubMed

    Gupta, Rajiv K; Padmanabhan, Thallam V

    2011-01-01

    Initial stability at the placement and development of osseointegration are two major issues for implant survival. Implant stability is a mechanical phenomenon which is related to the local bone quality and quantity, type of implant, and placement technique used. The application of a simple, clinically applicable, non-invasive test to assess implant stability and osseointegration is considered highly desirable. Resonance frequency analysis (RFA) is one of such techniques which is most frequently used now days. The aim of this paper was to review and analyze critically the current available literature in the field of RFA, and to also discuss based on scientific evidence, the prognostic value of RFA to detect implants at risk of failure. A search was made using the PubMed database to find all the literature published on "Resonance frequency analysis for implant stability" till date. Articles discussed in vivo or in vitro studies comparing RFA with other methods of implant stability measurement and articles discussing its reliability were thoroughly reviewed and discussed. A limited number of clinical reports were found. Various studies have demonstrated the feasibility and predictability of the technique. However, most of these articles are based on retrospective data or uncontrolled cases. Randomized, prospective, parallel-armed longitudinal human trials are based on short-term results and long-term follow up are still scarce in this field. Nonetheless, from available literature, it may be concluded that RFA technique evaluates implant stability as a function of stiffness of the implant bone interface and is influenced by factors such as bone type, exposed implant height above the alveolar crest. Resonance frequency analysis could serve as a non-invasive diagnostic tool for detecting the implant stability of dental implants during the healing stages and in subsequent routine follow up care after treatment. Future studies, preferably randomized, prospective

  12. Frequency domain nonlinear optics

    NASA Astrophysics Data System (ADS)

    Legare, Francois

    2016-05-01

    The universal dilemma of gain narrowing occurring in fs amplifiers prevents ultra-high power lasers from delivering few-cycle pulses. This problem is overcome by a new amplification concept: Frequency domain Optical Parametric Amplification - FOPA. It enables simultaneous up-scaling of peak power and amplified spectral bandwidth and can be performed at any wavelength range of conventional amplification schemes, however, with the capability to amplify single cycles of light. The key idea for amplification of octave-spanning spectra without loss of spectral bandwidth is to amplify the broad spectrum ``slice by slice'' in the frequency domain, i.e. in the Fourier plane of a 4f-setup. The striking advantages of this scheme, are its capability to amplify (more than) one octave of bandwidth without shorting the corresponding pulse duration. This is because ultrabroadband phase matching is not defined by the properties of the nonlinear crystal employed but the number of crystals employed. In the same manner, to increase the output energy one simply has to increase the spectral extension in the Fourier plane and to add one more crystal. Thus, increasing pulse energy and shortening its duration accompany each other. A proof of principle experiment was carried out at ALLS on the sub-two cycle IR beam line and yielded record breaking performance in the field of few-cycle IR lasers. 100 μJ two-cycle pulses from a hollow core fibre compression setup were amplified to 1.43mJ without distorting spatial or temporal properties. Pulse duration at the input of FOPA and after FOPA remains the same. Recently, we have started upgrading this system to be pumped by 250 mJ to reach 40 mJ two-cycle IR few-cycle pulses and latest results will be presented at the conference. Furthermore, the extension of the concept of FOPA to other nonlinear optical processes will be discussed. Frequency domain nonlinear optics.

  13. Microwave Frequency Polarizers

    NASA Technical Reports Server (NTRS)

    Ha, Vien The; Mirel, Paul; Kogut, Alan J.

    2013-01-01

    This article describes the fabrication and analysis of microwave frequency polarizing grids. The grids are designed to measure polarization from the cosmic microwave background. It is effective in the range of 500 to 1500 micron wavelength. It is cryogenic compatible and highly robust to high load impacts. Each grid is fabricated using an array of different assembly processes which vary in the types of tension mechanisms to the shape and size of the grids. We provide a comprehensive study on the analysis of the grids' wire heights, diameters, and spacing.

  14. High frequency electromagnetic tomography

    SciTech Connect

    Daily, W.; Ramirez, A.; Ueng, T.; Latorre, R.

    1989-09-01

    An experiment was conducted in G Tunnel at the Nevada Test Site to evaluate high frequency electromagnetic tomography as a candidate for in situ monitoring of hydrology in the near field of a heater placed in densely welded tuff. Tomographs of 200 MHz electromagnetic permittivity were made for several planes between boreholes. Data were taken before the heater was turned on, during heating and during cooldown of the rockmass. This data is interpreted to yield maps of changes in water content of the rockmass as a function of time. This interpretation is based on laboratory measurement of electromagnetic permittivity as a function of water content for densely welded tuff. 8 refs., 6 figs.

  15. Frequency agile relativistic magnetrons

    SciTech Connect

    Levine, J.S.; Harteneck, B.D.; Price, H.D.

    1995-11-01

    The authors are developing a family of frequency agile relativistic magnetrons to continuously cover the bands from 1 to 3 GHz. They have achieved tuning ranges of > 33%. The magnetrons have been operated repetitively in burst mode at rates up to 100 pps for 10 sec. Power is extracted from two resonators, and is in the range of 400--600 MW, fairly flat across the tuning bandwidth. They are using a network of phase shifters and 3-dB hybrids to combine the power into a single arm and to provide a continuously adjustable attenuator.

  16. High-frequency ventilation.

    PubMed

    Crawford, M R

    1986-08-01

    Over the last six years high-frequency ventilation has been extensively evaluated both in the clinical and laboratory settings. It is now no longer the great mystery it once was, and it is now no longer believed (as many had hoped), that it will solve all the problems associated with mechanical pulmonary ventilation. Although the technique is safe and appears to cause no harm even in the long term, it has not yet been shown to offer any major advantages over conventional mechanical ventilation. PMID:3530042

  17. RADIO FREQUENCY ATTENUATOR

    DOEpatents

    Giordano, S.

    1963-11-12

    A high peak power level r-f attenuator that is readily and easily insertable along a coaxial cable having an inner conductor and an outer annular conductor without breaking the ends thereof is presented. Spaced first and second flares in the outer conductor face each other with a slidable cylindrical outer conductor portion therebetween. Dielectric means, such as water, contact the cable between the flares to attenuate the radio-frequency energy received thereby. The cylindrical outer conductor portion is slidable to adjust the voltage standing wave ratio to a low level, and one of the flares is slidable to adjust the attenuation level. An integral dielectric container is also provided. (AFC)

  18. Frequency shifts of high frequency p-modes

    NASA Technical Reports Server (NTRS)

    Jain, Rekha

    1995-01-01

    Frequency shifts of high frequency p-modes during the solar cycle are calculated for a non-magnetic polytrope convection zone model. An isothermal chromospheric atmosphere threaded by a uniform horizontal magnetic field is correlated to this model. The relevant observations of such frequency changes are discussed. The calculated simultaneous changes in the field strength and chromospheric temperature result in the frequency shifts that are similar to those of the observations.

  19. Frequency selective bolometers

    NASA Astrophysics Data System (ADS)

    Kowitt, M. S.; Fixsen, D. J.; Goldin, A.; Meyer, S. S.

    1996-10-01

    We propose a concept for radiometry in the millimeter, the submillimeter, and the far-IR spectral regions, the frequency selective bolometer (FSB). This system uses a bolometer as a coupled element of a tuned quasi-optical interference filter in which the absorption, the transmission, and the reflection characteristics of the filter depend on the frequency in a controlled manner. Several FSB's can be cascaded within a straight light pipe to produce a high-efficiency, compact, multiband radiometer. A prototype design is presented together with its anticipated performance based on a one-dimensional transmission-line model. Instruments based on FSB technology should have several advantages over current multiband bolometric radiometers including smaller and more compact cryogenic optics, reduced demands on cryostat size and weight, high coupling efficiency, minimum constraints on the geometry in the focal plane. An FSB system can be configured as a multiband, close-packed focal-plane array, permitting efficient use of the throughput of a telescope.

  20. Laser-frequency multiplication

    SciTech Connect

    Not Available

    1991-11-01

    A high quality mode locked pulse train was obtained at 9.55 micrometers, the CO2 wavelength chosen for frequency doubling into the atmospheric window at 4.8 micrometers. The pulse train consists of a 3 micro sec burst of 1.5 nsec pulses separated by 40 nsec, in a TEM(00) mode and with a total energy of 100 mJ. The pulse intensity without focussing is about 3 MW/sq.cm., already quite close to the target intensity of 10 MW/sq.cm. for frequency doubling in a AgGaSe2 crystal. The mode-locked train is obtained by intracavity modulation at 12.5 MHz using a germanium crystal driven with a power of about 30 Watts. Line selection is achieved firstly by the use of a 0.92 mm thick CaF2 plate at the Brewster angle within the cavity, which completely suppresses 10.6 micrometer band radiation. Secondly, a particular rotational line, the P20 at 9.55 micrometers, is selected by the injection of a continuous beam is mode-matched to the pulsed laser cavity using a long focal length lens, and for best line-locking it is necessary to fine tune the length of the pulsed laser resonator. Injection causes substantial depression of the gain switched spike.

  1. High-frequency ECG

    NASA Technical Reports Server (NTRS)

    Tragardh, Elin; Schlegel, Todd T.

    2006-01-01

    The standard ECG is by convention limited to 0.05-150 Hz, but higher frequencies are also present in the ECG signal. With high-resolution technology, it is possible to record and analyze these higher frequencies. The highest amplitudes of the high-frequency components are found within the QRS complex. In past years, the term "high frequency", "high fidelity", and "wideband electrocardiography" have been used by several investigators to refer to the process of recording ECGs with an extended bandwidth of up to 1000 Hz. Several investigators have tried to analyze HF-QRS with the hope that additional features seen in the QRS complex would provide information enhancing the diagnostic value of the ECG. The development of computerized ECG-recording devices that made it possible to record ECG signals with high resolution in both time and amplitude, as well as better possibilities to store and process the signals digitally, offered new methods for analysis. Different techniques to extract the HF-QRS have been described. Several bandwidths and filter types have been applied for the extraction as well as different signal-averaging techniques for noise reduction. There is no standard method for acquiring and quantifying HF-QRS. The physiological mechanisms underlying HF-QRS are still not fully understood. One theory is that HF-QRS are related to the conduction velocity and the fragmentation of the depolarization wave in the myocardium. In a three-dimensional model of the ventricles with a fractal conduction system it was shown that high numbers of splitting branches are associated with HF-QRS. In this experiment, it was also shown that the changes seen in HF-QRS in patients with myocardial ischemia might be due to the slowing of the conduction velocity in the region of ischemia. This mechanism has been tested by Watanabe et al by infusing sodium channel blockers into the left anterior descending artery in dogs. In their study, 60 unipolar ECGs were recorded from the entire

  2. Time, Frequency and Physical Measurement.

    ERIC Educational Resources Information Center

    Hellwig, Helmut; And Others

    1978-01-01

    Describes several developments in atomic clocks and frequency standards pointing out the feasibility and practicality in adopting a unified standard of time and frequency to replace other base standards of length, mass, and temperature. (GA)

  3. Firewater system inadvertent actuation frequencies

    SciTech Connect

    Schroeder, J.A.; Eide, S.A.

    1993-04-01

    This paper presents some recommended generic values for fire protection system inadvertent actuation frequencies. The frequencies are based on actual data from Department of Energy and commercial reactor plant facilities.

  4. Firewater system inadvertent actuation frequencies

    SciTech Connect

    Schroeder, J.A. ); Eide, S.A. )

    1993-01-01

    This paper presents some recommended generic values for fire protection system inadvertent actuation frequencies. The frequencies are based on actual data from Department of Energy and commercial reactor plant facilities.

  5. Frequency mixer having ferromagnetic film

    DOEpatents

    Khitun, Alexander; Roshchin, Igor V.; Galatsis, Kosmas; Bao, Mingqiang; Wang, Kang L.

    2016-03-29

    A frequency conversion device, which may include a radiofrequency (RF) mixer device, includes a substrate and a ferromagnetic film disposed over a surface of the substrate. An insulator is disposed over the ferromagnetic film and at least one microstrip antenna is disposed over the insulator. The ferromagnetic film provides a non-linear response to the frequency conversion device. The frequency conversion device may be used for signal mixing and amplification. The frequency conversion device may also be used in data encryption applications.

  6. FREQUENCY STABILIZING SYSTEM

    DOEpatents

    Kerns, Q.A.; Anderson, O.A.

    1960-05-01

    An electronic control circuit is described in which a first signal frequency is held in synchronization with a second varying reference signal. The circuit receives the first and second signals as inputs and produces an output signal having an amplitude dependent upon rate of phase change between the two signals and a polarity dependent on direction of the phase change. The output may thus serve as a correction signal for maintaining the desired synchronization. The response of the system is not dependent on relative phase angle between the two compared signals. By having practically no capacitance in the circuit, there is minimum delay between occurrence of a phase shift and a response in the output signal and therefore very fast synchronization is effected.

  7. Frequency mixing crystal

    DOEpatents

    Ebbers, Christopher A.; Davis, Laura E.; Webb, Mark

    1992-01-01

    In a laser system for converting infrared laser light waves to visible light comprising a source of infrared laser light waves and means of harmoic generation associated therewith for production of light waves at integral multiples of the frequency of the original wave, the improvement of said means of harmonic generation comprising a crystal having the chemical formula X.sub.2 Y(NO.sub.3).sub.5 .multidot.2 nZ.sub.2 o wherein X is selected from the group consisting of Li, Na, K, Rb, Cs, and Tl; Y is selected from the group consisting of Sc, Y, La, Ce, Nd, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga, and In; Z is selected from the group consisting of H and D; and n ranges from 0 to 4.

  8. Frequency doubling crystals

    DOEpatents

    Wang, Francis; Velsko, Stephan P.

    1989-01-01

    A systematic approach to the production of frequency conversion crystals is described in which a chiral molecule has attached to it a "harmonic generating unit" which contributes to the noncentrosymmetry of the molecule. Certain preferred embodiments of such harmonic generating units include carboxylate, guanadyly and imidazolyl units. Certain preferred crystals include L-arginine fluoride, deuterated L-arginine fluoride, L-arginine chloride monohydrate, L-arginine acetate, dithallium tartrate, ammonium N-acetyl valine, N-acetyl tyrosine and N-acetyl hydroxyproline. Chemical modifications of the chiral molecule, such as deuteration, halogenation and controlled counterion substitution are available to adapt the dispersive properties of a crystal in a particular wavelength region.

  9. Flying radio frequency undulator

    SciTech Connect

    Kuzikov, S. V.; Vikharev, A. A.; Savilov, A. V.

    2014-07-21

    A concept for the room-temperature rf undulator, designed to produce coherent X-ray radiation by means of a relatively low-energy electron beam and pulsed mm-wavelength radiation, is proposed. The “flying” undulator is a high-power short rf pulse co-propagating together with a relativistic electron bunch in a helically corrugated waveguide. The electrons wiggle in the rf field of the −1st spatial harmonic with the phase velocity directed in the opposite direction in respect to the bunch velocity, so that particles can irradiate high-frequency Compton's photons. A high group velocity (close to the speed of light) ensures long cooperative motion of the particles and the co-propagating rf pulse.

  10. Radio frequency coaxial feedthrough

    DOEpatents

    Owens, Thomas L.

    1989-01-17

    An improved radio frequency coaxial transmission line vacuum feed-through provided based on the use of a half-wavelength annular dielectric pressure barrier disk, or multiple disks comprising an effective half wavelength structure to eliminate reflections from the barrier surfaces. Gas-tight seals are formed about the outer and inner diameter surfaces of the barrier disk using a sealing technique which generates radial forces sufficient to form seals by forcing the conductor walls against the surfaces of the barrier disks in a manner which does not deform the radii of the inner and outer conductors, thereby preventing enhancement of the electric field at the barrier faces which limits voltage and power handling capabilities of a feedthrough.

  11. High frequency nanotube oscillator

    DOEpatents

    Peng, Haibing; Zettl, Alexander K.

    2012-02-21

    A tunable nanostructure such as a nanotube is used to make an electromechanical oscillator. The mechanically oscillating nanotube can be provided with inertial clamps in the form of metal beads. The metal beads serve to clamp the nanotube so that the fundamental resonance frequency is in the microwave range, i.e., greater than at least 1 GHz, and up to 4 GHz and beyond. An electric current can be run through the nanotube to cause the metal beads to move along the nanotube and changing the length of the intervening nanotube segments. The oscillator can operate at ambient temperature and in air without significant loss of resonance quality. The nanotube is can be fabricated in a semiconductor style process and the device can be provided with source, drain, and gate electrodes, which may be connected to appropriate circuitry for driving and measuring the oscillation. Novel driving and measuring circuits are also disclosed.

  12. Instantaneous Frequency Attribute Comparison

    NASA Astrophysics Data System (ADS)

    Yedlin, M. J.; Margrave, G. F.; Ben Horin, Y.

    2013-12-01

    The instantaneous seismic data attribute provides a different means of seismic interpretation, for all types of seismic data. It first came to the fore in exploration seismology in the classic paper of Taner et al (1979), entitled " Complex seismic trace analysis". Subsequently a vast literature has been accumulated on the subject, which has been given an excellent review by Barnes (1992). In this research we will compare two different methods of computation of the instantaneous frequency. The first method is based on the original idea of Taner et al (1979) and utilizes the derivative of the instantaneous phase of the analytic signal. The second method is based on the computation of the power centroid of the time-frequency spectrum, obtained using either the Gabor Transform as computed by Margrave et al (2011) or the Stockwell Transform as described by Stockwell et al (1996). We will apply both methods to exploration seismic data and the DPRK events recorded in 2006 and 2013. In applying the classical analytic signal technique, which is known to be unstable, due to the division of the square of the envelope, we will incorporate the stabilization and smoothing method proposed in the two paper of Fomel (2007). This method employs linear inverse theory regularization coupled with the application of an appropriate data smoother. The centroid method application is straightforward and is based on the very complete theoretical analysis provided in elegant fashion by Cohen (1995). While the results of the two methods are very similar, noticeable differences are seen at the data edges. This is most likely due to the edge effects of the smoothing operator in the Fomel method, which is more computationally intensive, when an optimal search of the regularization parameter is done. An advantage of the centroid method is the intrinsic smoothing of the data, which is inherent in the sliding window application used in all Short-Time Fourier Transform methods. The Fomel technique

  13. High-Frequency Gated Oscillator

    NASA Technical Reports Server (NTRS)

    Berard, C. A.

    1982-01-01

    New gated oscillator generates bursts of high-frequency sine waves, square waves, and triangular waves in response to control signals. Each burst starts at zero phase, with tight tolerances on signal amplitude and frequency. Frequencies in megahertz range are made possible by using high-speed comparators and high-speed flip-flop as fast-response threshold detector.

  14. Frequency sensitivity for video compression

    NASA Astrophysics Data System (ADS)

    Seo, Guiwon; Lee, Jonghwa; Lee, Chulhee

    2014-03-01

    We investigate the frequency sensitivity of the human visual system, which reacts differently at different frequencies in video coding. Based on this observation, we used different quantization steps for different frequency components in order to explore the possibility of improving coding efficiency while maintaining perceptual video quality. In other words, small quantization steps were used for sensitive frequency components while large quantization steps were used for less sensitive frequency components. We performed subjective testing to examine the perceptual video quality of video sequences encoded by the proposed method. The experimental results showed that a reduction in bitrate is possible without causing a decrease in perceptual video quality.

  15. Frequency-bin entangled photons

    SciTech Connect

    Olislager, L.; Emplit, P.; Nguyen, A. T.; Massar, S.; Merolla, J.-M.; Huy, K. Phan

    2010-07-15

    A monochromatic laser pumping a parametric down-conversion crystal generates frequency-entangled photon pairs. We study this experimentally by addressing such frequency-entangled photons at telecommunication wavelengths (around 1550 nm) with fiber-optics components such as electro-optic phase modulators and narrow-band frequency filters. The theory underlying our approach uses the notion of frequency-bin entanglement. Our results show that the phase modulators address coherently up to eleven frequency bins, leading to an interference pattern which can violate by more than five standard deviations a Bell inequality adapted to our setup.

  16. Influence of modulation frequency in rubidium cell frequency standards

    NASA Technical Reports Server (NTRS)

    Audoin, C.; Viennet, J.; Cyr, N.; Vanier, J.

    1983-01-01

    The error signal which is used to control the frequency of the quartz crystal oscillator of a passive rubidium cell frequency standard is considered. The value of the slope of this signal, for an interrogation frequency close to the atomic transition frequency is calculated and measured for various phase (or frequency) modulation waveforms, and for several values of the modulation frequency. A theoretical analysis is made using a model which applies to a system in which the optical pumping rate, the relaxation rates and the RF field are homogeneous. Results are given for sine-wave phase modulation, square-wave frequency modulation and square-wave phase modulation. The influence of the modulation frequency on the slope of the error signal is specified. It is shown that the modulation frequency can be chosen as large as twice the non-saturated full-width at half-maximum without a drastic loss of the sensitivity to an offset of the interrogation frequency from center line, provided that the power saturation factor and the amplitude of modulation are properly adjusted.

  17. Mid-infrared frequency combs

    NASA Astrophysics Data System (ADS)

    Schliesser, Albert; Picqué, Nathalie; Hänsch, Theodor W.

    2012-07-01

    Laser frequency combs are coherent light sources that emit a broad spectrum of discrete, evenly spaced narrow lines whose absolute frequency can be measured to within the accuracy of an atomic clock. Their development in the near-infrared and visible domains has revolutionized frequency metrology while also providing numerous unexpected opportunities in other fields such as astronomy and attosecond science. Researchers are now exploring how to extend frequency comb techniques to the mid-infrared spectral region. Versatile mid-infrared frequency comb generators based on novel laser gain media, nonlinear frequency conversion or microresonators promise to significantly expand the applications of frequency combs. In particular, novel approaches to molecular spectroscopy in the 'fingerprint region', with dramatically improved precision, sensitivity, recording time and/or spectral bandwidth may lead to new discoveries in the various fields relevant to molecular science.

  18. A Biochemical Magic Frequency

    NASA Technical Reports Server (NTRS)

    Weber, Arthur L.

    1993-01-01

    Life is composed principally of four classes of biomolecules - protein, nucleic acid, polysaccharide and lipid. Using 1) estimates of the reducing equivalents (electron pairs) needed to synthesize these biomolecules from carbon dioxide, and 2) measurements of the molecular composition of different organisms, we calculated the average number of electron pairs required for the reduction of carbon dioxide to biological carbon (electron pairs/carbon atom). These calculations showed that the carbon of the Earths biosphere is at the reduction level of formaldehyde that requires 2 electron pairs/carbon atom to be synthesized from carbon dioxide. This was also the reduction level of carbon of individual organisms, except for those that stored large amounts of fuel as lipid. Since this chemical property of life is easily discovered and probably universal, it's most likely known by other intelligent life in the universe. It could be the one thing we know about other carbon-based life in the universe, and the one thing that other intelligent life knows about us. We believe this common knowledge that formaldehyde represents the reduction level of life's carbon could lead to the selection of the 72.83814 GHz line of the 0,0,0,1,0,1 ground-state rotational transition of formaldehyde as a frequency for interstellar communication.

  19. Flood frequency in Alaska

    USGS Publications Warehouse

    Childers, J.M.

    1970-01-01

    Records of peak discharge at 183 sites were used to study flood frequency in Alaska. The vast size of Alaska, its great ranges of physiography, and the lack of data for much of the State precluded a comprehensive analysis of all flood determinants. Peak stream discharges, where gaging-station records were available, were analyzed for 2-year, 5-year, 10-year, 25-year, and 50-year average-recurrence intervals. A regional analysis of the flood characteristics by multiple-regression methods gave a set of equations that can be used to estimate floods of selected recurrence intervals up to 50 years for any site on any stream in Alaska. The equations relate floods to drainage-basin characteristics. The study indicates that in Alaska the 50-year flood can be estimated from 10-year gaging- station records with a standard error of 22 percent whereas the 50-year flood can be estimated from the regression equation with a standard error of 53 percent. Also, maximum known floods at more than 500 gaging stations and miscellaneous sites in Alaska were related to drainage-area size. An envelope curve of 500 cubic feet per second per square mile covered all but 2 floods in the State.

  20. High spectral purity Kerr frequency comb radio frequency photonic oscillator.

    PubMed

    Liang, W; Eliyahu, D; Ilchenko, V S; Savchenkov, A A; Matsko, A B; Seidel, D; Maleki, L

    2015-01-01

    Femtosecond laser-based generation of radio frequency signals has produced astonishing improvements in achievable spectral purity, one of the basic features characterizing the performance of an radio frequency oscillator. Kerr frequency combs hold promise for transforming these lab-scale oscillators to chip-scale level. In this work we demonstrate a miniature 10 GHz radio frequency photonic oscillator characterized with phase noise better than -60 dBc Hz(-1) at 10 Hz, -90 dBc Hz(-1) at 100 Hz and -170 dBc Hz(-1) at 10 MHz. The frequency stability of this device, as represented by Allan deviation measurements, is at the level of 10(-10) at 1-100 s integration time-orders of magnitude better than existing radio frequency photonic devices of similar size, weight and power consumption. PMID:26260955

  1. High spectral purity Kerr frequency comb radio frequency photonic oscillator

    PubMed Central

    Liang, W.; Eliyahu, D.; Ilchenko, V. S.; Savchenkov, A. A.; Matsko, A. B.; Seidel, D.; Maleki, L.

    2015-01-01

    Femtosecond laser-based generation of radio frequency signals has produced astonishing improvements in achievable spectral purity, one of the basic features characterizing the performance of an radio frequency oscillator. Kerr frequency combs hold promise for transforming these lab-scale oscillators to chip-scale level. In this work we demonstrate a miniature 10 GHz radio frequency photonic oscillator characterized with phase noise better than −60 dBc Hz−1 at 10 Hz, −90 dBc Hz−1 at 100 Hz and −170 dBc Hz−1 at 10 MHz. The frequency stability of this device, as represented by Allan deviation measurements, is at the level of 10−10 at 1–100 s integration time—orders of magnitude better than existing radio frequency photonic devices of similar size, weight and power consumption. PMID:26260955

  2. High spectral purity Kerr frequency comb radio frequency photonic oscillator

    NASA Astrophysics Data System (ADS)

    Liang, W.; Eliyahu, D.; Ilchenko, V. S.; Savchenkov, A. A.; Matsko, A. B.; Seidel, D.; Maleki, L.

    2015-08-01

    Femtosecond laser-based generation of radio frequency signals has produced astonishing improvements in achievable spectral purity, one of the basic features characterizing the performance of an radio frequency oscillator. Kerr frequency combs hold promise for transforming these lab-scale oscillators to chip-scale level. In this work we demonstrate a miniature 10 GHz radio frequency photonic oscillator characterized with phase noise better than -60 dBc Hz-1 at 10 Hz, -90 dBc Hz-1 at 100 Hz and -170 dBc Hz-1 at 10 MHz. The frequency stability of this device, as represented by Allan deviation measurements, is at the level of 10-10 at 1-100 s integration time--orders of magnitude better than existing radio frequency photonic devices of similar size, weight and power consumption.

  3. Operational frequency stability of rubidium and cesium frequency standards

    NASA Technical Reports Server (NTRS)

    Lavery, J. E.

    1973-01-01

    The frequency stabilities under operational conditions of several commercially available rubidium and cesium frequency standards were determined from experimental data for frequency averaging times from 10 to the 7th power s and are presented in table and graph form. For frequency averaging times between 10 to the 5th power and 10 to the 7th power s, the rubidium standards tested have a stability of between 10 to the minus 12th power and 5 x 10 to the minus 12th power, while the cesium standards have a stability of between 2 x 10 to the minus 13th power and 5 x 10 to the minus 13th power.

  4. Light beam frequency comb generator

    DOEpatents

    Priatko, Gordon J.; Kaskey, Jeffrey A.

    1992-01-01

    A light beam frequency comb generator uses an acousto-optic modulator to generate a plurality of light beams with frequencies which are uniformly separated and possess common noise and drift characteristics. A well collimated monochromatic input light beam is passed through this modulator to produce a set of both frequency shifted and unshifted optical beams. An optical system directs one or more frequency shifted beams along a path which is parallel to the path of the input light beam such that the frequency shifted beams are made incident on the modulator proximate to but separated from the point of incidence of the input light beam. After the beam is thus returned to and passed through the modulator repeatedly, a plurality of mutually parallel beams are generated which are frequency-shifted different numbers of times and possess common noise and drift characteristics.

  5. Light beam frequency comb generator

    DOEpatents

    Priatko, G.J.; Kaskey, J.A.

    1992-11-24

    A light beam frequency comb generator uses an acousto-optic modulator to generate a plurality of light beams with frequencies which are uniformly separated and possess common noise and drift characteristics. A well collimated monochromatic input light beam is passed through this modulator to produce a set of both frequency shifted and unshifted optical beams. An optical system directs one or more frequency shifted beams along a path which is parallel to the path of the input light beam such that the frequency shifted beams are made incident on the modulator proximate to but separated from the point of incidence of the input light beam. After the beam is thus returned to and passed through the modulator repeatedly, a plurality of mutually parallel beams are generated which are frequency-shifted different numbers of times and possess common noise and drift characteristics. 2 figs.

  6. Effective switching frequency multiplier inverter

    SciTech Connect

    Su, Gui-Jia; Peng, Fang Z.

    2007-08-07

    A switching frequency multiplier inverter for low inductance machines that uses parallel connection of switches and each switch is independently controlled according to a pulse width modulation scheme. The effective switching frequency is multiplied by the number of switches connected in parallel while each individual switch operates within its limit of switching frequency. This technique can also be used for other power converters such as DC/DC, AC/DC converters.

  7. Frequency-Shift Hearing Aid

    NASA Technical Reports Server (NTRS)

    Weinstein, Leonard M.

    1994-01-01

    Proposed hearing aid maps spectrum of speech into band of lower frequencies at which ear remains sensitive. By redirecting normal speech frequencies into frequency band from 100 to 1,500 Hz, hearing aid allows people to understand normal conversation, including telephone calls. Principle operation of hearing aid adapted to other uses such as, clearing up noisy telephone or radio communication. In addition, loud-speakers more easily understood in presence of high background noise.

  8. International Frequency Control Symposium. Proceedings.

    NASA Astrophysics Data System (ADS)

    The following topics are dealt with: sensors; atomic clocks; space applications; GPS; stability; synchronisation; time keeping; BAW resonators; SAW resonators; STW; frequency control; oscillators; and aging.

  9. Automatic oscillator frequency control system

    NASA Technical Reports Server (NTRS)

    Smith, S. F. (Inventor)

    1985-01-01

    A frequency control system makes an initial correction of the frequency of its own timing circuit after comparison against a frequency of known accuracy and then sequentially checks and corrects the frequencies of several voltage controlled local oscillator circuits. The timing circuit initiates the machine cycles of a central processing unit which applies a frequency index to an input register in a modulo-sum frequency divider stage and enables a multiplexer to clock an accumulator register in the divider stage with a cyclical signal derived from the oscillator circuit being checked. Upon expiration of the interval, the processing unit compares the remainder held as the contents of the accumulator against a stored zero error constant and applies an appropriate correction word to a correction stage to shift the frequency of the oscillator being checked. A signal from the accumulator register may be used to drive a phase plane ROM and, with periodic shifts in the applied frequency index, to provide frequency shift keying of the resultant output signal. Interposition of a phase adder between the accumulator register and phase plane ROM permits phase shift keying of the output signal by periodic variation in the value of a phase index applied to one input of the phase adder.

  10. Frequency-Tracking-Error Detector

    NASA Technical Reports Server (NTRS)

    Randall, Richard L.

    1990-01-01

    Frequency-tracking-error detector compares average period of output signal from band-pass tracking filter with average period of signal of frequency 100 f(sub 0) that controls center frequency f(sub 0) of tracking filter. Measures difference between f(sub 0) and frequency of one of periodic components in output of bearing sensor. Bearing sensor is accelerometer, strain gauge, or deflectometer mounted on bearing housing. Detector part of system of electronic equipment used to measure vibrations in bearings in rotating machinery.

  11. Broadband optical serrodyne frequency shifting.

    PubMed

    Johnson, D M S; Hogan, J M; Chiow, S-w; Kasevich, M A

    2010-03-01

    We demonstrate serrodyne frequency shifting of light from 200 MHz to 1.2 GHz with an efficiency of better than 60%. The frequency shift is imparted by an electro-optic phase modulator driven by a high-frequency high-fidelity sawtooth waveform that is passively generated by a commercially available nonlinear transmission line. We also implement a push-pull configuration using two serrodyne-driven phase modulators, allowing for continuous tuning between -1.6 GHz and +1.6 GHz. Compared with competing technologies, this technique is simple and robust, and it offers the largest available tuning range in this frequency band. PMID:20195339

  12. Atomic frequency standards for ultra-high-frequency stability

    NASA Technical Reports Server (NTRS)

    Maleki, L.; Prestage, J. D.; Dick, G. J.

    1987-01-01

    The general features of the Hg-199(+) trapped-ion frequency standard are outlined and compared to other atomic frequency standards, especially the hydrogen maser. The points discussed are those which make the trapped Hg-199(+) standard attractive: high line Q, reduced sensitivity to external magnetic fields, and simplicity of state selection, among others.

  13. Frequency Discrimination in Young Infants.

    ERIC Educational Resources Information Center

    Olsho, Lynne Werner; And Others

    Frequency difference thresholds were determined for fourteen 4- to 9-month-old infants (mean age, 6 months 10 days) using a discrimination learning paradigm, following a one-up, two-down staircase procedure. The subject heard 500 msec tone bursts repeated at a rate of one per sec, with a fixed standard frequency. At various points in this pulse…

  14. Frequency conversion of structured light

    PubMed Central

    Steinlechner, Fabian; Hermosa, Nathaniel; Pruneri, Valerio; Torres, Juan P.

    2016-01-01

    Coherent frequency conversion of structured light, i.e. the ability to manipulate the carrier frequency of a wave front without distorting its spatial phase and intensity profile, provides the opportunity for numerous novel applications in photonic technology and fundamental science. In particular, frequency conversion of spatial modes carrying orbital angular momentum can be exploited in sub-wavelength resolution nano-optics and coherent imaging at a wavelength different from that used to illuminate an object. Moreover, coherent frequency conversion will be crucial for interfacing information stored in the high-dimensional spatial structure of single and entangled photons with various constituents of quantum networks. In this work, we demonstrate frequency conversion of structured light from the near infrared (803 nm) to the visible (527 nm). The conversion scheme is based on sum-frequency generation in a periodically poled lithium niobate crystal pumped with a 1540-nm Gaussian beam. We observe frequency-converted fields that exhibit a high degree of similarity with the input field and verify the coherence of the frequency-conversion process via mode projection measurements with a phase mask and a single-mode fiber. Our results demonstrate the suitability of exploiting the technique for applications in quantum information processing and coherent imaging. PMID:26875448

  15. Gaming Frequency and Academic Performance

    ERIC Educational Resources Information Center

    Ip, Barry; Jacobs, Gabriel; Watkins, Alan

    2008-01-01

    There are numerous claims that playing computer and video games may be educationally beneficial, but there has been little formal investigation into whether or not the frequency of exposure to such games actually affects academic performance. This paper explores the issue by analysing the relationships between gaming frequency--measured as the…

  16. Frequency conversion of structured light

    NASA Astrophysics Data System (ADS)

    Steinlechner, Fabian; Hermosa, Nathaniel; Pruneri, Valerio; Torres, Juan P.

    2016-02-01

    Coherent frequency conversion of structured light, i.e. the ability to manipulate the carrier frequency of a wave front without distorting its spatial phase and intensity profile, provides the opportunity for numerous novel applications in photonic technology and fundamental science. In particular, frequency conversion of spatial modes carrying orbital angular momentum can be exploited in sub-wavelength resolution nano-optics and coherent imaging at a wavelength different from that used to illuminate an object. Moreover, coherent frequency conversion will be crucial for interfacing information stored in the high-dimensional spatial structure of single and entangled photons with various constituents of quantum networks. In this work, we demonstrate frequency conversion of structured light from the near infrared (803 nm) to the visible (527 nm). The conversion scheme is based on sum-frequency generation in a periodically poled lithium niobate crystal pumped with a 1540-nm Gaussian beam. We observe frequency-converted fields that exhibit a high degree of similarity with the input field and verify the coherence of the frequency-conversion process via mode projection measurements with a phase mask and a single-mode fiber. Our results demonstrate the suitability of exploiting the technique for applications in quantum information processing and coherent imaging.

  17. Frequency conversion of structured light.

    PubMed

    Steinlechner, Fabian; Hermosa, Nathaniel; Pruneri, Valerio; Torres, Juan P

    2016-01-01

    Coherent frequency conversion of structured light, i.e. the ability to manipulate the carrier frequency of a wave front without distorting its spatial phase and intensity profile, provides the opportunity for numerous novel applications in photonic technology and fundamental science. In particular, frequency conversion of spatial modes carrying orbital angular momentum can be exploited in sub-wavelength resolution nano-optics and coherent imaging at a wavelength different from that used to illuminate an object. Moreover, coherent frequency conversion will be crucial for interfacing information stored in the high-dimensional spatial structure of single and entangled photons with various constituents of quantum networks. In this work, we demonstrate frequency conversion of structured light from the near infrared (803 nm) to the visible (527 nm). The conversion scheme is based on sum-frequency generation in a periodically poled lithium niobate crystal pumped with a 1540-nm Gaussian beam. We observe frequency-converted fields that exhibit a high degree of similarity with the input field and verify the coherence of the frequency-conversion process via mode projection measurements with a phase mask and a single-mode fiber. Our results demonstrate the suitability of exploiting the technique for applications in quantum information processing and coherent imaging. PMID:26875448

  18. Lexical Frequency in Sign Languages

    ERIC Educational Resources Information Center

    Johnston, Trevor

    2012-01-01

    Measures of lexical frequency presuppose the existence of corpora, but true machine-readable corpora of sign languages (SLs) are only now being created. Lexical frequency ratings for SLs are needed because there has been a heavy reliance on the interpretation of results of psycholinguistic and neurolinguistic experiments in the SL research…

  19. Stabilized radio-frequency quadrupole

    DOEpatents

    Lancaster, H.D.; Fugitt, J.A.; Howard, D.R.

    1982-09-29

    A long-vane stabilized radio frequency resonator for accelerating charged particles and including means defining a radio frequency resonator cavity, a plurality of long vanes mounted in the defining means for dividing the cavity into sections, and means interconnecting opposing ones of the plurality of vanes for stabilizing the resonator.

  20. Contour Integration across Spatial Frequency

    ERIC Educational Resources Information Center

    Persike, Malte; Olzak, Lynn A.; Meinhardt, Gunter

    2009-01-01

    Association field models of contour integration suggest that local band-pass elements are spatially grouped to global contours within limited bands of spatial frequency (Field, Hayes, & Hess, 1993). While results for local orientation and spacing variation render support for AF models, effects of spatial frequency (SF) have rarely been addressed.…

  1. Variable frequency microwave excited plasma

    SciTech Connect

    Gathi, Z.; Wei, J.; Garard, S.; Lauf, R.J.; Clausing, R.; McMillan, A.

    1995-12-31

    This paper reports on the use of an agile frequency source in generating plasma. A Traveling Wave Tube (TWT) provides approximately one octave bandwidth and variable power level up to 2 KW. By controlling the frequency, efficient coupling to the load (materials and/or plasma) can be maintained even as the load is changing in properties or position. Furthermore, the variable frequency power source allows the localization of the plasma discharge in precise areas of interest to specific processes. The excitation frequencies can be continuously swept to scan the plasma across an arbitrary-shaped target surface. Plasma generation and position control is reviewed and experimental results on variable frequency microwave excited plasma are presented.

  2. Robust adiabatic sum frequency conversion.

    PubMed

    Suchowski, Haim; Prabhudesai, Vaibhav; Oron, Dan; Arie, Ady; Silberberg, Yaron

    2009-07-20

    We discuss theoretically and demonstrate experimentally the robustness of the adiabatic sum frequency conversion method. This technique, borrowed from an analogous scheme of robust population transfer in atomic physics and nuclear magnetic resonance, enables the achievement of nearly full frequency conversion in a sum frequency generation process for a bandwidth up to two orders of magnitude wider than in conventional conversion schemes. We show that this scheme is robust to variations in the parameters of both the nonlinear crystal and of the incoming light. These include the crystal temperature, the frequency of the incoming field, the pump intensity, the crystal length and the angle of incidence. Also, we show that this extremely broad bandwidth can be tuned to higher or lower central wavelengths by changing either the pump frequency or the crystal temperature. The detailed study of the properties of this converter is done using the Landau-Zener theory dealing with the adiabatic transitions in two level systems. PMID:19654679

  3. Frequency synthesizers for telemetry receivers

    NASA Astrophysics Data System (ADS)

    Stirling, Ronald C.

    1990-07-01

    The design of a frequency synthesizer is presented for telemetry receivers. The synthesizer contains two phase-locked loops, each with a programmable frequency counter, and incorporates fractional frequency synthesis but does not use a phase accumulator. The selected receiver design has a variable reference loop operating as a part of the output loop. Within the synthesizer, a single VTO generates the output frequency that is voltage-tunable from 375-656 MHz. The single-sideband phase noise is measured with an HP 8566B spectrum analyzer, and the receiver's bit error rate (BER) is measured with a carrier frequency of 250 MHz, synthesized LO at 410 MHz, and the conditions of BPSK, NRZ-L, and 2.3 kHz bit rate. The phase noise measurement limits and the BER performance data are presented in tabular form.

  4. Laser Spectroscopy and Frequency Combs

    NASA Astrophysics Data System (ADS)

    Hänsch, Theodor W.; Picqué, Nathalie

    2013-12-01

    The spectrum of a frequency comb, commonly generated by a mode-locked femtosecond laser consists of several hundred thousand precisely evenly spaced spectral lines. Such laser frequency combs have revolutionized the art measuring the frequency of light, and they provide the long-missing clockwork for optical atomic clocks. The invention of the frequency comb technique has been motivated by precision laser spectroscopy of the simple hydrogen atom. The availability of commercial instruments is facilitating the evolution of new applications far beyond the original purpose. Laser combs are becoming powerful instruments for broadband molecular spectroscopy by dramatically improving the resolution and recording speed of Fourier spectrometers and by creating new opportunities for highly multiplexed nonlinear spectroscopy, such as two-photon spectroscopy or coherent Raman spectroscopy. Other emerging applications of frequency combs range from fundamental research in astronomy, chemistry, or attosecond science to telecommunications and satellite navigation.

  5. Frequency fluctuations in silicon nanoresonators

    NASA Astrophysics Data System (ADS)

    Sansa, Marc; Sage, Eric; Bullard, Elizabeth C.; Gély, Marc; Alava, Thomas; Colinet, Eric; Naik, Akshay K.; Villanueva, Luis Guillermo; Duraffourg, Laurent; Roukes, Michael L.; Jourdan, Guillaume; Hentz, Sébastien

    2016-06-01

    Frequency stability is key to the performance of nanoresonators. This stability is thought to reach a limit with the resonator's ability to resolve thermally induced vibrations. Although measurements and predictions of resonator stability usually disregard fluctuations in the mechanical frequency response, these fluctuations have recently attracted considerable theoretical interest. However, their existence is very difficult to demonstrate experimentally. Here, through a literature review, we show that all studies of frequency stability report values several orders of magnitude larger than the limit imposed by thermomechanical noise. We studied a monocrystalline silicon nanoresonator at room temperature and found a similar discrepancy. We propose a new method to show that this was due to the presence of frequency fluctuations, of unexpected level. The fluctuations were not due to the instrumentation system, or to any other of the known sources investigated. These results challenge our current understanding of frequency fluctuations and call for a change in practices.

  6. Frequency fluctuations in silicon nanoresonators.

    PubMed

    Sansa, Marc; Sage, Eric; Bullard, Elizabeth C; Gély, Marc; Alava, Thomas; Colinet, Eric; Naik, Akshay K; Villanueva, Luis Guillermo; Duraffourg, Laurent; Roukes, Michael L; Jourdan, Guillaume; Hentz, Sébastien

    2016-06-01

    Frequency stability is key to the performance of nanoresonators. This stability is thought to reach a limit with the resonator's ability to resolve thermally induced vibrations. Although measurements and predictions of resonator stability usually disregard fluctuations in the mechanical frequency response, these fluctuations have recently attracted considerable theoretical interest. However, their existence is very difficult to demonstrate experimentally. Here, through a literature review, we show that all studies of frequency stability report values several orders of magnitude larger than the limit imposed by thermomechanical noise. We studied a monocrystalline silicon nanoresonator at room temperature and found a similar discrepancy. We propose a new method to show that this was due to the presence of frequency fluctuations, of unexpected level. The fluctuations were not due to the instrumentation system, or to any other of the known sources investigated. These results challenge our current understanding of frequency fluctuations and call for a change in practices. PMID:26925826

  7. Single-frequency tunable laser for pumping cesium frequency standards

    SciTech Connect

    Zhuravleva, O V; Ivanov, Andrei V; Leonovich, A I; Kurnosov, V D; Kurnosov, K V; Chernov, Roman V; Shishkov, V V; Pleshanov, S A

    2006-08-31

    A single-frequency tunable laser for pumping the cesium frequency standard is studied. It is shown experimentally that the laser emits at a single frequency despite the fact that a few longitudinal modes of the external cavity fall within the reflection band of a fibre Bragg grating (FBG) written in the optical fibre. The laser wavelength can be tuned by varying the pump current of the laser, its temperature, and the FBG temperature. The laser linewidth does not exceed 2 MHz for 10 mW of output power. (lasers)

  8. Geometrical representation of sum frequency generation and adiabatic frequency conversion

    NASA Astrophysics Data System (ADS)

    Suchowski, Haim; Oron, Dan; Arie, Ady; Silberberg, Yaron

    2008-12-01

    We present a geometrical representation of the process of sum frequency generation in the undepleted pump approximation, in analogy with the known optical Bloch equations. We use this analogy to propose a technique for achieving both high efficiency and large bandwidth in sum frequency conversion using the adiabatic inversion scheme. The process is analogous with rapid adiabatic passage in NMR, and adiabatic constraints are derived in this context. This adiabatic frequency conversion scheme is realized experimentally using an aperiodically poled potassium titanyl phosphate (KTP) device, where we achieved high efficiency signal-to-idler conversion over a bandwidth of 140nm .

  9. Acoustic resonance frequency locked photoacoustic spectrometer

    DOEpatents

    Pilgrim, Jeffrey S.; Bomse, David S.; Silver, Joel A.

    2003-09-09

    A photoacoustic spectroscopy method and apparatus for maintaining an acoustic source frequency on a sample cell resonance frequency comprising: providing an acoustic source to the sample cell, the acoustic source having a source frequency; repeatedly and continuously sweeping the source frequency across the resonance frequency at a sweep rate; and employing an odd-harmonic of the source frequency sweep rate to maintain the source frequency sweep centered on the resonance frequency.

  10. Surface-water-quality assessment of the lower Kansas River basin, Kansas and Nebraska; dissolved oxygen and Escherichia coli bacteria in streams during low flow, July 1988 through July 1989

    USGS Publications Warehouse

    Pope, L.M.

    1995-01-01

    respiratory demand in combination with reduced physical reaeration associated with extreme low flow probably also contributes to temporary, localized deficiencies. Densities of E. coli were determined at 57 surface-water sampling sites during the syn- optic survey in July 1988. Results indicate large regional differences in E. coli densities within the study unit. Densities orE. coli in water at 19 sites in the Big Blue River subbasin, exclusive of the Little Blue River subbasin, ranged from 120 to 260,000 col/100 mL (colonies per 100 milliliters), with a median density of 2,400 col/100 mL. Densities at the 11 sites in the Little Blue River ranged from 100 to 30,000 col/100 mL, with a median density of 940 col/100 mL. Densities at the 27 sites in the Kansas River subbasin ranged from less than 1 to 1,000 col/100 mL, with a median density of 88 col/100 mL. Densities at 84 percent of the sites in the Big Blue River subbasin exceeded the USEPA E. coli criterion of 576 col/100 mL for infrequently used full-body contact recreation, and 53 percent exceeded the 2,000 cot/I00 mL fecal coliform criterion for uses other than full-body contact established by the Kansas Department of Health and Environment. Densities at 73 percent of the sites in the Little Blue River subbasin exceeded the 576 col/100 mL E. coli criterion, and 36 percent exceeded the 2,000 col/100 mL fecal coliform criterion. Densities at one of the sites in the Kansas River subbasin exceeded the 576 col/100 mL E. coli criterion, and none exceeded the 2,000 col/100 mL fecal-coliform criterion. The largest densities of E. coli in the study unit were the result of discharges from municipal wastewater-treatment plants; however, densities in the Big Blue and Little Blue River subbasins were generally larger than those in the Kansas River subbasin. These larger densities in the Big Blue and Little Blue River subbasins may have been the result of irrigation return flow from fields where manure was used as a soil

  11. Monolithically integrated absolute frequency comb laser system

    DOEpatents

    Wanke, Michael C.

    2016-07-12

    Rather than down-convert optical frequencies, a QCL laser system directly generates a THz frequency comb in a compact monolithically integrated chip that can be locked to an absolute frequency without the need of a frequency-comb synthesizer. The monolithic, absolute frequency comb can provide a THz frequency reference and tool for high-resolution broad band spectroscopy.

  12. Active laser ranging with frequency transfer using frequency comb

    NASA Astrophysics Data System (ADS)

    Zhang, Hongyuan; Wei, Haoyun; Yang, Honglei; Li, Yan

    2016-05-01

    A comb-based active laser ranging scheme is proposed for enhanced distance resolution and a common time standard for the entire system. Three frequency combs with different repetition rates are used as light sources at the two ends where the distance is measured. Pulse positions are determined through asynchronous optical sampling and type II second harmonic generation. Results show that the system achieves a maximum residual of 379.6 nm and a standard deviation of 92.9 nm with 2000 averages over 23.6 m. Moreover, as for the frequency transfer, an atom clock and an adjustable signal generator, synchronized to the atom clock, are used as time standards for the two ends to appraise the frequency deviation introduced by the proposed system. The system achieves a residual fractional deviation of 1.3 × 10-16 for 1 s, allowing precise frequency transfer between the two clocks at the two ends.

  13. Medium-Frequency Pseudonoise Georadar

    NASA Technical Reports Server (NTRS)

    Arendt, G. Dickey; Carl, J. R.; Byerly, Kent A.; Amini, B. Jon

    2005-01-01

    Ground-probing radar systems featuring medium-frequency carrier signals phase-modulated by binary pseudonoise codes have been proposed. These systems would be used to locate and detect movements of subterranean surfaces; the primary intended application is in warning of the movement of underground water toward oil-well intake ports in time to shut down those ports to avoid pumping of water. Other potential applications include oil-well logging and monitoring of underground reservoirs. A typical prior georadar system operates at a carrier frequency of at least 50 MHz in order to provide useable range resolution. This frequency is too high for adequate penetration of many underground layers of interest. On the other hand, if the carrier frequency were to be reduced greatly to increase penetration, then bandwidth and thus range resolution would also have to be reduced, thereby rendering the system less useful. The proposed medium-frequency pseudonoise georadar systems would offer the advantage of greater penetration at lower carrier frequencies, but without the loss of resolution that would be incurred by operating typical prior georadar systems at lower frequencies.

  14. Laser frequency stabilization for LISA

    NASA Technical Reports Server (NTRS)

    Mueller, Guido; McNamara, Paul; Thorpe, Ira; Camp, Jordan

    2005-01-01

    The requirement on laser frequency noise in the Laser Interferometer Space Antenna (LISA) depends on the velocity and our knowledge of the position of each spacecraft of the interferometer. Currently it is assumed that the lasers must have a pre-stabilized frequency stability of 30Hz/square root of Hz over LISA'S most sensitive frequency band (3 mHz - 30 mHz). The intrinsic frequency stability of even the most stable com- mercial lasers is several orders of magnitude above this level. Therefore it is necessary to stabilize the laser frequency to an ultra-stable frequency reference which meets the LISA requirements. The baseline frequency reference for the LISA lasers are high finesse optical cavities based on ULE spacers. We measured the stability of two ULE spacer cavities with respect to each other. Our current best results show a noise floor at, or below, 30 Hz/square root of Hz above 3 mHz. In this report we describe the experimental layout of the entire experiment and discuss the limiting noise sources.

  15. Pulsed optically pumped frequency standard

    SciTech Connect

    Godone, Aldo; Micalizio, Salvatore; Levi, Filippo

    2004-08-01

    We reconsider the idea of a pulsed optically pumped frequency standard conceived in the early 1960s to eliminate the light-shift effect. The development of semiconductor lasers and of pulsed electronic techniques for atomic fountains and new theoretical findings allow an implementation of this idea which may lead to a frequency standard whose frequency stability is limited only by the thermal noise in the short term and by the temperature drift in the long term. We shall also show both theoretically and experimentally the possibility of doubling the atomic quality factor with respect to the classical Ramsey technique approach.

  16. Blazars at Low Radio Frequencies

    NASA Astrophysics Data System (ADS)

    Trüstedt, J.; Kadler, M.; Brüggen, M.; Falcke, H.; Heald, G.; McKean, J.; Mueller, C.; Ros, E.; Schulz, R.; Wilms, J.

    We explore the low radio-frequency properties of the MOJAVE 1 blazar sample using the LOFAR Multi-Frequency Snapshot Sky Survey (MSSS). We find the characteristically flat blazar spectrum to extend down to the LOFAR bands, demonstrating that the emission at these low radio frequencies is still dominated by relativistically beamed emission. As most sources remain unresolved at the MSSS angular resolution, we are reimaging these data using LOFAR baselines beyond the standard MSSS uv-range resulting in an angular resolution of ~24 arcsec. We present first LOFAR images of MOJAVE sources from this project.

  17. Microcontroller interrupts in frequency controlling

    NASA Astrophysics Data System (ADS)

    Panoiu, C.; Rob, R.; Panoiu, M.

    2015-06-01

    Present paper represents an educational software application that permits to measure the signals frequency. The application is accomplished in MicroC compiler that also permit to user to program a microcontroller PIC18F45K22 using a developing board EasyPICv7. An important issue of present application is to measure the frequency of an external signal that is acquired by an input pin of the microcontroller. The frequency value is displayed on the seven segment display provided by the developing board.

  18. Digital varying-frequency generator

    NASA Technical Reports Server (NTRS)

    Allen, M. J.

    1977-01-01

    Generator employs up/down counters, digital-to-analog converters, and integrator to determine frequency and time duration of output. Circuit can be used where varying signal must be controlled accurately over long period of time.

  19. High Frequency Electronic Packaging Technology

    NASA Technical Reports Server (NTRS)

    Herman, M.; Lowry, L.; Lee, K.; Kolawa, E.; Tulintseff, A.; Shalkhauser, K.; Whitaker, J.; Piket-May, M.

    1994-01-01

    Commercial and government communication, radar, and information systems face the challenge of cost and mass reduction via the application of advanced packaging technology. A majority of both government and industry support has been focused on low frequency digital electronics.

  20. Discussion of human resonant frequency

    NASA Astrophysics Data System (ADS)

    Brownjohn, James M. W.; Zheng, Xiahua

    2001-06-01

    Human bodies are often exposed to vertical vibrations when they are in the workplace or on vehicles. Prolonged exposure may cause undue stress and discomfort in the human body especially at its resonant frequency. By testing the response of the human body on a vibrating platform, many researchers found the human whole-body fundamental resonant frequency to be around 5 Hz. However, in recent years, an indirect method has been prosed which appears to increase the resonant frequency to approximately 10 Hz. To explain this discrepancy, experimental work was carried out in NTU. The study shows that the discrepancy lies in the vibration magnitude used in the tests. A definition of human natural frequency in terms of vibration magnitude is proposed.

  1. Frequency coded sensors incorporating tapers

    NASA Technical Reports Server (NTRS)

    Hines, Jacqueline H. (Inventor); Solie, Leland P. (Inventor)

    2010-01-01

    A surface acoustic wave device includes a piezoelectric substrate on which is formed a transducer that generates acoustic waves on the surface of the substrate from electrical waves received by the transducer. The waves are carried along an acoustic track to either a second transducer or a reflector. The transducers or transducer and reflector are formed of subsections that are constructed to operate at mutually different frequencies. The subsections of at least one of the transducers or transducer and reflector are out of alignment with respect to one another relative to the transverse of the propagation direction. The out of aligned subsections provide not only a frequency component but also a time to the signal output signal. Frequency response characteristics are improved. An alternative embodiment provides that the transducers and/or reflectors are continuously tapered instead of having discrete frequency subsections.

  2. Dual-frequency microwave antenna

    NASA Technical Reports Server (NTRS)

    Bathker, D. A.; Brunstein, S. A.; Ludwig, A. C.; Potter, P. D.

    1980-01-01

    Single antenna using two feed horns (one for receiving and radiation X-band signals, and one for S-band signals), in conjunction with ellipsoid reflector and dichronic plate, can accommodate two different frequencies simultaneously.

  3. Frequency regulator for synchronous generators

    DOEpatents

    Karlicek, Robert F.

    1982-01-01

    The present invention is directed to a novel frequency regulator which controls a generator output frequency for variations in both the input power to the generator and the power supplied to an uncontrolled external load. The present invention further includes over current and current balance protection devices which are relatively inexpensive to manufacture, which may be encapsulated to provide protection from the operating environment and which respond more quickly than previously known electromechanical devices.

  4. Prospects for atomic frequency standards

    NASA Technical Reports Server (NTRS)

    Audoin, C.

    1984-01-01

    The potentialities of different atomic frequency standards which are not yet into field operation, for most of them, but for which preliminary data, obtained in laboratory experiments, give confidence that they may improve greatly the present state of the art are described. The review will mainly cover the following devices: (1) cesium beam frequency standards with optical pumping and detection; (2) optically pumped rubidium cells; (3) magnesium beam; (4) cold hydrogen masers; and (5) traps with stored and cooled ions.

  5. The classical microwave frequency standards

    NASA Technical Reports Server (NTRS)

    Busca, Giovanni; Thomann, Pierre; Laurent-Guy, Bernier; Willemin, Philippe; Schweda, Hartmut S.

    1990-01-01

    Some key problems are presented encountered in the classical microwave frequency standards which are still not solved today. The point of view expressed benefits from the experience gained both in the industry and in the research lab, on the following classical microwave frequency standards: active and passive H, conventional and laser pumped Cs beam tube, small conventional and laser pumped Rubidium. The accent is put on the Rubidium standard.

  6. Low-Frequency Radioastronomy Basics

    NASA Astrophysics Data System (ADS)

    Zarka, P.

    2011-04-01

    With the many large instruments in construction or in project, the present epoch corresponds to a renewal of low-frequency radioastronomy. The field will attract new researchers and students not expert of the radioastronomy techniques. With this audience in mind, we present here a very brief introduction to radioastronomy basics, including propagation and polarization of low-frequency radio waves as well as instrumental aspects. Basic formulas are given. The references and internet links will allow the interested reader to go further.

  7. Frequency regulator for synchronous generators

    DOEpatents

    Karlicek, R.F.

    1982-08-10

    The present invention is directed to a novel frequency regulator which controls a generator output frequency for variations in both the input power to the generator and the power supplied to an uncontrolled external load. The present invention further includes over current and current balance protection devices which are relatively inexpensive to manufacture, which may be encapsulated to provide protection from the operating environment and which respond more quickly than previously known electromechanical devices. 11 figs.

  8. The measurement of optical frequencies

    NASA Astrophysics Data System (ADS)

    Hollberg, L.; Diddams, S.; Bartels, A.; Fortier, T.; Kim, K.

    2005-06-01

    Surprising as it might seem, it is possible to phase-coherently track, synthesize, count and divide optical frequencies of visible laser sources. In essence, the technologies described here now allow direct connection of basically any frequency from DC to 1000 THz. Modern 'self-referenced' femtosecond mode-locked lasers have enormously simplified the required technology. These revolutionary new systems build on a long history of optical frequency metrology that spans from the early days of the laser. The latest systems rely heavily on technologies previously developed for laser frequency stabilization, optical phase-locked-loops, nonlinear mixing, ultra-fast optics and precision opto-electronic metrology. Using examples we summarize some of the heroic efforts that led to the successful development of harmonic optical frequency chains. Those systems played critical roles in defining the speed of light and in redefining the metre. We then describe the present state-of-the-art technology in femtosecond laser frequency combs, their extraordinary performance capabilities and some of the latest results.

  9. Stepped frequency ground penetrating radar

    DOEpatents

    Vadnais, Kenneth G.; Bashforth, Michael B.; Lewallen, Tricia S.; Nammath, Sharyn R.

    1994-01-01

    A stepped frequency ground penetrating radar system is described comprising an RF signal generating section capable of producing stepped frequency signals in spaced and equal increments of time and frequency over a preselected bandwidth which serves as a common RF signal source for both a transmit portion and a receive portion of the system. In the transmit portion of the system the signal is processed into in-phase and quadrature signals which are then amplified and then transmitted toward a target. The reflected signals from the target are then received by a receive antenna and mixed with a reference signal from the common RF signal source in a mixer whose output is then fed through a low pass filter. The DC output, after amplification and demodulation, is digitized and converted into a frequency domain signal by a Fast Fourier Transform. A plot of the frequency domain signals from all of the stepped frequencies broadcast toward and received from the target yields information concerning the range (distance) and cross section (size) of the target.

  10. Parametric Effects of Word Frequency in Memory for Mixed Frequency Lists

    ERIC Educational Resources Information Center

    Lohnas, Lynn J.; Kahana, Michael J.

    2013-01-01

    The "word frequency paradox" refers to the finding that low frequency words are better recognized than high frequency words yet high frequency words are better recalled than low frequency words. Rather than comparing separate groups of low and high frequency words, we sought to quantify the functional relation between word frequency and…

  11. 47 CFR 87.375 - Frequencies.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Frequencies. 87.375 Section 87.375... Aeronautical Search and Rescue Stations § 87.375 Frequencies. (a) The frequency 123.100 MHz is available for... rescue station must be equipped to operate on this frequency. (b) The frequency 122.900 MHz is...

  12. 47 CFR 87.375 - Frequencies.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Frequencies. 87.375 Section 87.375... Aeronautical Search and Rescue Stations § 87.375 Frequencies. (a) The frequency 123.100 MHz is available for... rescue station must be equipped to operate on this frequency. (b) The frequency 122.900 MHz is...

  13. 47 CFR 74.464 - Frequency tolerance.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false Frequency tolerance. 74.464 Section 74.464....464 Frequency tolerance. For operations on frequencies above 25 MHz using authorized bandwidths up to... frequency of each station in compliance with the frequency tolerance requirements of § 90.213 of...

  14. 47 CFR 87.375 - Frequencies.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Frequencies. 87.375 Section 87.375... Aeronautical Search and Rescue Stations § 87.375 Frequencies. (a) The frequency 123.100 MHz is available for... rescue station must be equipped to operate on this frequency. (b) The frequency 122.900 MHz is...

  15. 47 CFR 5.303 - Frequencies.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 1 2013-10-01 2013-10-01 false Frequencies. 5.303 Section 5.303... Licenses § 5.303 Frequencies. Licensees may operate in any frequency band, except for frequency bands... licensees are permitted to operate in frequency bands above 38.6 GHz, unless these bands are listed...

  16. 47 CFR 87.375 - Frequencies.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Frequencies. 87.375 Section 87.375... Aeronautical Search and Rescue Stations § 87.375 Frequencies. (a) The frequency 123.100 MHz is available for... rescue station must be equipped to operate on this frequency. (b) The frequency 122.900 MHz is...

  17. 47 CFR 74.464 - Frequency tolerance.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Frequency tolerance. 74.464 Section 74.464....464 Frequency tolerance. For operations on frequencies above 25 MHz using authorized bandwidths up to... frequency of each station in compliance with the frequency tolerance requirements of § 90.213 of...

  18. 47 CFR 74.464 - Frequency tolerance.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Frequency tolerance. 74.464 Section 74.464....464 Frequency tolerance. For operations on frequencies above 25 MHz using authorized bandwidths up to... frequency of each station in compliance with the frequency tolerance requirements of § 90.213 of...

  19. 47 CFR 74.464 - Frequency tolerance.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Frequency tolerance. 74.464 Section 74.464....464 Frequency tolerance. For operations on frequencies above 25 MHz using authorized bandwidths up to... frequency of each station in compliance with the frequency tolerance requirements of § 90.213 of...

  20. 47 CFR 74.464 - Frequency tolerance.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false Frequency tolerance. 74.464 Section 74.464....464 Frequency tolerance. For operations on frequencies above 25 MHz using authorized bandwidths up to... frequency of each station in compliance with the frequency tolerance requirements of § 90.213 of...

  1. 47 CFR 87.375 - Frequencies.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Frequencies. 87.375 Section 87.375... Aeronautical Search and Rescue Stations § 87.375 Frequencies. (a) The frequency 123.100 MHz is available for... rescue station must be equipped to operate on this frequency. (b) The frequency 122.900 MHz is...

  2. Active Faraday optical frequency standard.

    PubMed

    Zhuang, Wei; Chen, Jingbiao

    2014-11-01

    We propose the mechanism of an active Faraday optical clock, and experimentally demonstrate an active Faraday optical frequency standard based on narrow bandwidth Faraday atomic filter by the method of velocity-selective optical pumping of cesium vapor. The center frequency of the active Faraday optical frequency standard is determined by the cesium 6 (2)S(1/2) F=4 to 6 (2)P(3/2) F'=4 and 5 crossover transition line. The optical heterodyne beat between two similar independent setups shows that the frequency linewidth reaches 281(23) Hz, which is 1.9×10(4) times smaller than the natural linewidth of the cesium 852-nm transition line. The maximum emitted light power reaches 75 μW. The active Faraday optical frequency standard reported here has advantages of narrow linewidth and reduced cavity pulling, which can readily be extended to other atomic transition lines of alkali and alkaline-earth metal atoms trapped in optical lattices at magic wavelengths, making it useful for new generation of optical atomic clocks. PMID:25361349

  3. Quantum Cascade Laser Frequency Combs

    NASA Astrophysics Data System (ADS)

    Faist, Jérôme; Villares, Gustavo; Scalari, Giacomo; Rösch, Markus; Bonzon, Christopher; Hugi, Andreas; Beck, Mattias

    2016-06-01

    It was recently demonstrated that broadband quantum cascade lasers can operate as frequency combs. As such, they operate under direct electrical pumping at both mid-infrared and THz frequencies, making them very attractive for dual-comb spectroscopy. Performance levels are continuously improving, with average powers over 100mW and frequency coverage of 100 cm-1 in the mid-infrared region. In the THz range, 10mW of average power and 600 GHz of frequency coverage are reported. As a result of the very short upper state lifetime of the gain medium, the mode proliferation in these sources arises from four-wave mixing rather than saturable absorption. As a result, their optical output is characterized by the tendency of small intensity modulation of the output power, and the relative phases of the modes to be similar to the ones of a frequency modulated laser. Recent results include the proof of comb operation down to a metrological level, the observation of a Schawlow-Townes broadened linewidth, as well as the first dual-comb spectroscopy measurements. The capability of the structure to integrate monothically nonlinear optical elements as well as to operate as a detector shows great promise for future chip integration of dual-comb systems.

  4. Frequency response of ice streams

    PubMed Central

    Williams, C. Rosie; Hindmarsh, Richard C. A.; Arthern, Robert J.

    2012-01-01

    Changes at the grounding line of ice streams have consequences for inland ice dynamics and hence sea level. Despite substantial evidence documenting upstream propagation of frontal change, the mechanisms by which these changes are transmitted inland are not well understood. In this vein, the frequency response of an idealized ice stream to periodic forcing in the downstream strain rate is examined for basally and laterally resisted ice streams using a one-dimensional, linearized membrane stress approximation. This reveals two distinct behavioural branches, which we find to correspond to different mechanisms of upstream velocity and thickness propagation, depending on the forcing frequency. At low frequencies (centennial to millennial periods), slope and thickness covary hundreds of kilometres inland, and the shallow-ice approximation is sufficient to explain upstream propagation, which occurs through changes in grounding-line flow and geometry. At high frequencies (decadal to sub-decadal periods), penetration distances are tens of kilometres; while velocity adjusts rapidly to such forcing, thickness varies little and upstream propagation occurs through the direct transmission of membrane stresses. Propagation properties vary significantly between 29 Antarctic ice streams considered. A square-wave function in frontal stress is explored by summing frequency solutions, simulating some aspects of the dynamical response to sudden ice-shelf change. PMID:23197934

  5. Transparency in nonlinear frequency conversion

    NASA Astrophysics Data System (ADS)

    Longhi, Stefano

    2016-04-01

    Suppression of wave scattering and the realization of transparency effects in engineered optical media and surfaces have attracted great attention in the past recent years. In this work the problem of transparency is considered for optical wave propagation in a nonlinear dielectric medium with second-order χ(2 ) susceptibility. Because of nonlinear interaction, a reference signal wave at carrier frequency ω1 can exchange power, thus being amplified or attenuated, when phase-matching conditions are satisfied and frequency conversion takes place. Therefore, rather generally the medium is not transparent to the signal wave because of "scattering" in the frequency domain. Here we show that broadband transparency, corresponding to the full absence of frequency conversion in spite of phase matching, can be observed for the signal wave in the process of sum frequency generation whenever the effective susceptibility χ(2 ) along the nonlinear medium is tailored following a suitable spatial apodization profile and the power level of the pump wave is properly tuned. While broadband transparency is observed under such conditions, the nonlinear medium is not invisible owing to an additional effective dispersion for the signal wave introduced by the nonlinear interaction.

  6. Variable frequency drive applications guide

    SciTech Connect

    Laloudakis, D.J.

    1991-10-01

    Traditionally, fans and pumps have been designed to be capable of handling the maximum demand of the system in which they are installed. However, quite often the actual demand can vary and it can be much lower than the original design capacity. These situations have been corrected in the past through additions of outlet dampers to fans or throttling valves to pumps. While these can be effective and simple controls they severely affect the efficiency of the system. Variable frequency (speed) is the most efficient means of capacity control. The most cost effective method of achieving variable speed capacity control is using AC adjustable frequency drives. AC adjustable frequency controls convert any fixed speed AC motor into an adjustable speed device. Adjusting the speed of a motor, by controlling the frequency of the AC power to that motor, reduces its horsepower requirements. According to pump and fan laws, capacity is proportional to speed while horsepower is proportional to the cube of the speed. Therefore, by reducing the speed of an AC motor by 20 percent the horsepower requirement is reduced by nearly 50 percent. Reduced speed through variable frequency control allows for flexibility of meeting changing weather and comfort requirements without operating costly equipment at full capacity.

  7. Frequency response of ice streams.

    PubMed

    Williams, C Rosie; Hindmarsh, Richard C A; Arthern, Robert J

    2012-11-01

    Changes at the grounding line of ice streams have consequences for inland ice dynamics and hence sea level. Despite substantial evidence documenting upstream propagation of frontal change, the mechanisms by which these changes are transmitted inland are not well understood. In this vein, the frequency response of an idealized ice stream to periodic forcing in the downstream strain rate is examined for basally and laterally resisted ice streams using a one-dimensional, linearized membrane stress approximation. This reveals two distinct behavioural branches, which we find to correspond to different mechanisms of upstream velocity and thickness propagation, depending on the forcing frequency. At low frequencies (centennial to millennial periods), slope and thickness covary hundreds of kilometres inland, and the shallow-ice approximation is sufficient to explain upstream propagation, which occurs through changes in grounding-line flow and geometry. At high frequencies (decadal to sub-decadal periods), penetration distances are tens of kilometres; while velocity adjusts rapidly to such forcing, thickness varies little and upstream propagation occurs through the direct transmission of membrane stresses. Propagation properties vary significantly between 29 Antarctic ice streams considered. A square-wave function in frontal stress is explored by summing frequency solutions, simulating some aspects of the dynamical response to sudden ice-shelf change. PMID:23197934

  8. Swept Frequency Laser Metrology System

    NASA Technical Reports Server (NTRS)

    Zhao, Feng (Inventor)

    2010-01-01

    A swept frequency laser ranging system having sub-micron accuracy that employs multiple common-path heterodyne interferometers, one coupled to a calibrated delay-line for use as an absolute reference for the ranging system. An exemplary embodiment uses two laser heterodyne interferometers to create two laser beams at two different frequencies to measure distance and motions of target(s). Heterodyne fringes generated from reflections off a reference fiducial X(sub R) and measurement (or target) fiducial X(sub M) are reflected back and are then detected by photodiodes. The measured phase changes Delta phi(sub R) and Delta phi (sub m) resulting from the laser frequency swept gives target position. The reference delay-line is the only absolute reference needed in the metrology system and this provides an ultra-stable reference and simple/economical system.

  9. Atomic frequency standards at NICT

    NASA Astrophysics Data System (ADS)

    Ido, T.; Fujieda, M.; Hachisu, H.; Hayasaka, K.; Kajita, M.; Kojima, R.; Kumagai, M.; Locke, C.; Li, Y.; Matsubara, K.; Nogami, A.; Shiga, N.; Yamaguchi, A.; Koyama, Y.; Hosokawa, M.; Hanado, Y.

    2011-10-01

    Various activities of atomic frequency standards studied in National Institute of Information and Communications Technology (NICT) are briefly reviewed. After BIPM accepted the first cesium fountain clock in NICT as a reference to determine International Atomic Time (TAI), efforts to further reduce the uncertainty of collision shifts are ongoing. A second fountain clock using atomic molasses is being built to enable the operation with less atomic density. Single ion clock using calcium has been pursued for several years in NICT. The absolute frequency measured in 2008 has CIPM to adopt the Ca+ clock transition as a part of the list of radiation (LoR) to realize the meter. Sr lattice clock has started its operation last year. The absolute frequency agreed well with those obtained in other institutes. Study of stable cavities to stabilize clock lasers are also introduced.

  10. Variable frequency microwave heating apparatus

    DOEpatents

    Bible, Don W.; Lauf, Robert J.; Johnson, Arvid C.; Thigpen, Larry T.

    1999-01-01

    A variable frequency microwave heating apparatus (10) designed to allow modulation of the frequency of the microwaves introduced into a multi-mode microwave cavity (34) for testing or other selected applications. The variable frequency microwave heating apparatus (10) includes a microwave signal generator (12) and a high-power microwave amplifier (20) or a high-power microwave oscillator (14). A power supply (22) is provided for operation of the high-power microwave oscillator (14) or microwave amplifier (20). A directional coupler (24) is provided for detecting the direction and amplitude of signals incident upon and reflected from the microwave cavity (34). A first power meter (30) is provided for measuring the power delivered to the microwave furnace (32). A second power meter (26) detects the magnitude of reflected power. Reflected power is dissipated in the reflected power load (28).

  11. Frequency Synthesizer For Tracking Filter

    NASA Technical Reports Server (NTRS)

    Randall, Richard L.

    1990-01-01

    Digital frequency-synthesizing subsystem generates trains of pulses, free of jitter, for use as frequency-control signals in tracking filters. Part of assembly of electronic equipment used to measure vibrations in bearings in rotating machinery. Designed to meet requirements for tracking narrow-band cage-rotation and ball-pass components of vibrations, as discussed in "Frequency-Tracking Error Detector" (MFS-29538) and "Ball-Pass Cage-Modulation Detector" (MFS-29539). Synthesizer includes preset counter, output of which controls signal for ball-pass filter. Input to this preset counter updated every 2 microseconds: responds almost immediately, effectively eliminating relatively long response time (lock-in time) and phase jitter.

  12. The instantaneous frequency rate spectrogram

    NASA Astrophysics Data System (ADS)

    Czarnecki, Krzysztof

    2016-01-01

    An accelerogram of the instantaneous phase of signal components referred to as an instantaneous frequency rate spectrogram (IFRS) is presented as a joint time-frequency distribution. The distribution is directly obtained by processing the short-time Fourier transform (STFT) locally. A novel approach to amplitude demodulation based upon the reassignment method is introduced as a useful by-product. Additionally, an estimator of energy density versus the instantaneous frequency rate (IFR) is proposed and referred to as the IFR profile. The energy density is estimated based upon both the classical energy spectrogram and the IFRS smoothened by the median filter. Moreover, the impact of an analyzing window width, additive white Gaussian noise and observation time is tested. Finally, the introduced method is used for the analysis of the acoustic emission of an automotive engine. The recording of the engine of a Lamborghini Gallardo is analyzed as an example.

  13. High frequency gyrokinetic particle simulation

    SciTech Connect

    Kolesnikov, R. A.; Lee, W. W.; Qin, H.; Startsev, E.

    2007-07-15

    The gyrokinetic approach for arbitrary frequency dynamics in magnetized plasmas is explored, using the gyrocenter-gauge kinetic theory. Contrary to low-frequency gyrokinetics, which views each particle as a rigid charged ring, arbitrary frequency response of a particle is described by a quickly changing Kruskal ring. This approach allows the separation of gyrocenter and gyrophase responses and thus allows for, in many situations, larger time steps for the gyrocenter push than for the gyrophase push. The gyrophase response which determines the shape of Kruskal rings can be described by a Fourier series in gyrophase for some problems, thus allowing control over the cyclotron harmonics at which the plasma responds. A computational algorithm for particle-in-cell simulation based on this concept has been developed. An example of the ion Bernstein wave is used to illustrate its numerical properties, and comparison with a direct Lorentz-force approach is presented.

  14. Gabor: frequency, time, and memory.

    PubMed

    Korpel, A

    1982-10-15

    Dennis Gabor is well-known as the inventor of holography. Less well-known, perhaps, are his contributions to other areas. Yet they are important and, like holography, characteristic of his foresight. In the field of communications, Gabor investigated the classic dichotomy of time and frequency. Guided by analogies to quantum mechanics, he postulated a set of elementary signals and made brilliant use of time-frequency diagrams to analyze communication systems. Applying his theories to acoustics, he researched the mechanism of hearing, defining acoustical quanta in the process and inventing early prototype frequency compressors and expanders. In a completely different field, Gabor, inspired by some early work of Longuet-Higgins on models for holographic temporal recall in the brain, suggested novel approaches which contributed significantly to the understanding of associative memories. In this paper we describe Gabor's pioneering work in these areas and trace the subsequent development by himself and others. PMID:20396288

  15. Bichromatically pumped microresonator frequency combs

    NASA Astrophysics Data System (ADS)

    Hansson, T.; Wabnitz, S.

    2014-07-01

    A study is made of the nonlinear dynamics of bichromatically pumped microresonator Kerr frequency combs described by a driven and damped nonlinear Schrödinger equation, with an additional degree of freedom in the form of the modulation frequency. A truncated four-wave model is derived for the pump modes and the dominant sideband pair, which is found to be able to describe much of the essential dynamical behavior of the full equation. The stability of stationary states within the four-wave model is investigated, and numerical simulations are made to demonstrate that a large range of solutions, including cavity solitons, are possible beyond previously considered low-intensity patterns.

  16. Mobile high frequency vibrator system

    SciTech Connect

    Fair, D.W.; Buller, P.L.

    1985-01-08

    A carrier mounted seismic vibrator system that is primarily adapted for generation of high force, high frequency seismic energy into an earth medium. The apparatus includes first and second vibrators as supported by first and second lift systems disposed in tandem juxtaposition generally centrally in said vehicle, and the lift systems are designed to maintain equal hold-down force on the vibrator coupling baseplates without exceeding the weight of the carrier vehicle. The juxtaposed vibrators are then energized in synchronized relationship to propagate increased amounts of higher frequency seismic energy into an earth medium.

  17. Rotation frequency relay for hydrogenerator

    SciTech Connect

    Matveev, V.V.

    1980-09-01

    The rotation frequency relay (RFR) is one of the most critical elements of automatic control system of the hydrogenerators. Accurate fixing of braking, subsynchronous and acceleration angular speeds contribute to operational reliability of many units of mechanical and electrical parts of the hydrogenerator and vise versa. Both experimental and theoretical investigations were performed on hydrogenerators. It was concluded that the rotation frequency relay, where an integrated voltage of the regulator generator is used as reference voltage and the elements of comparison are executed on the operating amplifiers, has a fairly high accuracy and stability of settings, and practically does not require regulation for manufacture and operation.

  18. DSS 13 frequency stability tests

    NASA Technical Reports Server (NTRS)

    Otoshi, T. Y.; Franco, M. M.

    1987-01-01

    In a previous article, the results of frequency stability tests at DSS 13 were presented in table form for tau = 1000 s for the test period May 1985 through March 1986. This article is a continuation of that initial report and presents specially selected Allan sigma (square root of variance) plots of each of the subsystem test previously reported. An additional result obtained from tests performed during July 1986 was included for completeness. The Allan sigma plots are useful in that frequency stability information is not only given for tau = 1000 s, but for tau values in the regions of 1, 100, 500, and 2000 s as well.

  19. Power enhanced frequency conversion system

    NASA Technical Reports Server (NTRS)

    Sanders, Steven (Inventor); Lang, Robert J. (Inventor); Waarts, Robert G. (Inventor)

    2001-01-01

    A frequency conversion system includes at least one source providing a first near-IR wavelength output including a gain medium for providing high power amplification, such as double clad fiber amplifier, a double clad fiber laser or a semiconductor tapered amplifier to enhance the power output level of the near-IR wavelength output. The NFM device may be a difference frequency mixing (DFM) device or an optical parametric oscillation (OPO) device. Pump powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Ra-man/Brillouin amplifier or oscillator between the high power source and the NFM device.

  20. Two-frequency Ramsey interferometry

    SciTech Connect

    Seidel, D.; Muga, J. G.

    2007-02-15

    We investigate Ramsey interferometry for two separated fields oscillating with different frequencies. It is shown that the interplay between average and relative detuning leads to interference effects not present in the standard, single-frequency setup. For a large free-flight time of ground-state atoms before entering the first field region, the Ramsey fringes with respect to the relative detuning become much narrower than the usual ones. The stability of these effects with respect to phase or velocity fluctuations is discussed.

  1. Organ vascularity and metastatic frequency.

    PubMed Central

    Weiss, L.; Haydock, K.; Pickren, J. W.; Lane, W. W.

    1980-01-01

    The "hemodynamic" or "mechanical" theory proposes that the frequency of metastases in different organs is primarily determined by the numbers of cancer cells delivered to them in their arterial blood. This theory has not yet been adequately tested in man because reproducible, noninvasive measurements of organ blood flow have only recently become available. Correlation between these data and the metastatic frequency in 10 organs, in groups of patients with primary cancers in 15 anatomic sites, has therefore been sought. No correlation was obtained between metastatic frequency and organ weights, blood volumes, blood volumes per gram, "transit times," or blood flow. However, correlations significant at the 4-8% level were obtained between organ blood flow per gram and metastatic frequency in 4 of 5 groups of primary cancers with initial venous drainage into the portal system, compared with 1 of 10 draining into the caval system. At present, no definitive explanation can be offered for the apparent compliance of one set of primary cancers with the "hemodynamic" theory of metastasis, but not the others. PMID:7446696

  2. High frequency integrated MOS filters

    NASA Technical Reports Server (NTRS)

    Peterson, C.

    1990-01-01

    Several techniques exist for implementing integrated MOS filters. These techniques fit into the general categories of sampled and tuned continuous-time filters. Advantages and limitations of each approach are discussed. This paper focuses primarily on the high frequency capabilities of MOS integrated filters.

  3. Frequency agile optical parametric oscillator

    DOEpatents

    Velsko, Stephan P.

    1998-01-01

    The frequency agile OPO device converts a fixed wavelength pump laser beam to arbitrary wavelengths within a specified range with pulse to pulse agility, at a rate limited only by the repetition rate of the pump laser. Uses of this invention include Laser radar, LIDAR, active remote sensing of effluents/pollutants, environmental monitoring, antisensor lasers, and spectroscopy.

  4. Frequency agile optical parametric oscillator

    DOEpatents

    Velsko, S.P.

    1998-11-24

    The frequency agile OPO device converts a fixed wavelength pump laser beam to arbitrary wavelengths within a specified range with pulse to pulse agility, at a rate limited only by the repetition rate of the pump laser. Uses of this invention include Laser radar, LIDAR, active remote sensing of effluents/pollutants, environmental monitoring, antisensor lasers, and spectroscopy. 14 figs.

  5. Connecting colors to flexible frequencies

    NASA Astrophysics Data System (ADS)

    Shaw, Mike

    2010-11-01

    Here is a simple way to reinforce the relationships among wavelength, frequency, and color in the visible light spectrum. All that is required is a 3-ft section of plastic or metal electric dryer venting hose, cans of red and violet spray paint, a couple of 5-in elastic bands, and a metric ruler.

  6. OPTIMUM FREQUENCY OF CALIBRATION MONITORING

    EPA Science Inventory

    The paper develops an algorithm by which to compute the optimal frequency of calibration monitoring to minimize the total cost of analyzing a set of samples and the required calibration standards. Optimum calibration monitoring is needed because of the high cost and calibration d...

  7. Frequency Allocation; The Radio Spectrum.

    ERIC Educational Resources Information Center

    Federal Communications Commission, Washington, DC.

    The Federal Communications Commission (FCC) assigns segments of the radio spectrum to categories of users, and specific frequencies within each segment to individual users. Since demand for channel space exceeds supply, the process is complex. The radio spectrum can be compared to a long ruler: the portion from 10-540 kiloHertz has been set aside…

  8. Judged Frequency of Lethal Events.

    ERIC Educational Resources Information Center

    Lichtenstein, Sarah; And Others

    1978-01-01

    College student and adult subjects were studied in five experimental formats to gauge how well people can estimate the frequency of death from specific causes. Subjects tended to overestimate the rate of rare causes, underestimate likely causes, and be influenced by drama or vividness. (Author/SJL)

  9. Low Frequency Radio Experiment (LORE)

    NASA Astrophysics Data System (ADS)

    Manoharan, P. K.; Naidu, Arun; Joshi, B. C.; Roy, Jayashree; Kate, G.; Pethe, Kaiwalya; Galande, Shridhar; Jamadar, Sachin; Mahajan, S. P.; Patil, R. A.

    2016-03-01

    In this paper, we present a case study of Low Frequency Radio Experiment (LORE) payload to probe the corona and the solar disturbances at solar offsets greater than 2 solar radii, i.e., at frequencies below 30 MHz. The LORE can be complimentary to the planned Indian solar mission, “Aditya-L1” and its other payloads as well as synergistic to ground-based interplanetary scintillation (IPS) observations, which are routinely carried out by the Ooty Radio Telescope. We discuss the baseline design and technical details of the proposed LORE and its particular suitability for providing measurements on the detailed time and frequency structure of fast drifting type-III and slow drifting type-II radio bursts with unprecedented time and frequency resolutions. We also brief the gonio-polarimetry, which is possible with better-designed antennas and state-of-the-art electronics, employing FPGAs and an intelligent data management system. These would enable us to make a wide range of studies, such as nonlinear plasma processes in the Sun-Earth distance, in-situ radio emission from coronal mass ejections (CMEs), interplanetary CME driven shocks, nature of ICMEs driving decelerating IP shocks and space weather effects of solar wind interaction regions.

  10. Pulsed Single Frequency Fiber Lasers

    NASA Astrophysics Data System (ADS)

    Jiang, Shibin

    2016-06-01

    Pulsed single frequency fiber lasers with mJ level near 1 micron, 1.55 micron and 2 micron wavelengths were demonstrated by using our proprietary highly doped fibers. These fiber lasers exhibit excellent long term stable operation with M2<1.2.

  11. Spatial frequency domain error budget

    SciTech Connect

    Hauschildt, H; Krulewich, D

    1998-08-27

    The aim of this paper is to describe a methodology for designing and characterizing machines used to manufacture or inspect parts with spatial-frequency-based specifications. At Lawrence Livermore National Laboratory, one of our responsibilities is to design or select the appropriate machine tools to produce advanced optical and weapons systems. Recently, many of the component tolerances for these systems have been specified in terms of the spatial frequency content of residual errors on the surface. We typically use an error budget as a sensitivity analysis tool to ensure that the parts manufactured by a machine will meet the specified component tolerances. Error budgets provide the formalism whereby we account for all sources of uncertainty in a process, and sum them to arrive at a net prediction of how "precisely" a manufactured component can meet a target specification. Using the error budget, we are able to minimize risk during initial stages by ensuring that the machine will produce components that meet specifications before the machine is actually built or purchased. However, the current error budgeting procedure provides no formal mechanism for designing machines that can produce parts with spatial-frequency-based specifications. The output from the current error budgeting procedure is a single number estimating the net worst case or RMS error on the work piece. This procedure has limited ability to differentiate between low spatial frequency form errors versus high frequency surface finish errors. Therefore the current error budgeting procedure can lead us to reject a machine that is adequate or accept a machine that is inadequate. This paper will describe a new error budgeting methodology to aid in the design and characterization of machines used to manufacture or inspect parts with spatial-frequency-based specifications. The output from this new procedure is the continuous spatial frequency content of errors that result on a machined part. If the machine

  12. Ionospheric very low frequency transmitter

    SciTech Connect

    Kuo, Spencer P.

    2015-02-15

    The theme of this paper is to establish a reliable ionospheric very low frequency (VLF) transmitter, which is also broad band. Two approaches are studied that generate VLF waves in the ionosphere. The first, classic approach employs a ground-based HF heater to directly modulate the high latitude ionospheric, or auroral electrojet. In the classic approach, the intensity-modulated HF heater induces an alternating current in the electrojet, which serves as a virtual antenna to transmit VLF waves. The spatial and temporal variations of the electrojet impact the reliability of the classic approach. The second, beat-wave approach also employs a ground-based HF heater; however, in this approach, the heater operates in a continuous wave mode at two HF frequencies separated by the desired VLF frequency. Theories for both approaches are formulated, calculations performed with numerical model simulations, and the calculations are compared to experimental results. Theory for the classic approach shows that an HF heater wave, intensity-modulated at VLF, modulates the electron temperature dependent electrical conductivity of the ionospheric electrojet, which, in turn, induces an ac electrojet current. Thus, the electrojet becomes a virtual VLF antenna. The numerical results show that the radiation intensity of the modulated electrojet decreases with an increase in VLF radiation frequency. Theory for the beat wave approach shows that the VLF radiation intensity depends upon the HF heater intensity rather than the electrojet strength, and yet this approach can also modulate the electrojet when present. HF heater experiments were conducted for both the intensity modulated and beat wave approaches. VLF radiations were generated and the experimental results confirm the numerical simulations. Theory and experimental results both show that in the absence of the electrojet, VLF radiation from the F-region is generated via the beat wave approach. Additionally, the beat wave approach

  13. Generation of multiple optical frequencies referenced to a frequency comb for precision free-space frequency transfer

    NASA Astrophysics Data System (ADS)

    Chun, Byung Jae; Kang, Hyun Jay; Kim, Young-Jin; Kim, Seung-Woo

    2016-03-01

    Generating multiple optical frequencies referenced to the frequency standard is an important task in optical clock dissemination and optical communication. An apparatus for frequency-comb-referenced generation of multiple optical frequencies is demonstrated for high-precision free-space transfer of multiple optical frequencies. The relative linewidth and frequency instability at each channel corresponds to sub-1 Hz and 1.06×10-15 at 10 s averaging time, respectively. During the free-space transfer, the refractive index change of transmission media caused by atmospheric turbulences induces phase and frequency noise on optical frequencies. These phase and frequency noise causes induced linewidth broadening and frequency shift in optical frequencies which can disturb the accurate frequency transfer. The proposed feedback loop with acousto-optic modulator can monitor and compensate phase/frequency noise on optical frequencies. As a result, a frequency-comb-referenced single optical mode is compensated with a high signal to noise ratio (SNR) of 80 dB. By sharing the same optical paths, this feedback loop is confirmed to be successfully transferred to the neighboring wavelength channels (a 100 GHz spaced channel). This result confirms our proposed system can transfer optical frequencies to the remote site in free-space without performance degradation.

  14. 47 CFR 74.503 - Frequency selection.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false Frequency selection. 74.503 Section 74.503... § 74.503 Frequency selection. (a) Each application for a new station or change in an existing station shall be specific with regard to frequency. In general, the lowest suitable frequency will be...

  15. 47 CFR 74.661 - Frequency tolerance.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Frequency tolerance. 74.661 Section 74.661... Stations § 74.661 Frequency tolerance. Stations in this service shall maintain the carrier frequency of each authorized transmitter to within the following percentage of the assigned frequency....

  16. 47 CFR 87.303 - Frequencies.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Frequencies. 87.303 Section 87.303... Flight Test Stations § 87.303 Frequencies. (a) These frequencies are available for assignment to flight....375 3 123.450 3 (b) These additional frequencies are available for assignment only to flight...

  17. 47 CFR 87.217 - Frequencies.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Frequencies. 87.217 Section 87.217... Aeronautical Advisory Stations (Unicoms) § 87.217 Frequencies. (a) Only one unicom frequency will be assigned at any one airport. Applicants must request a particular frequency, which will be taken...

  18. 47 CFR 80.45 - Frequencies.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Frequencies. 80.45 Section 80.45... MARITIME SERVICES Applications and Licenses § 80.45 Frequencies. For applications other than ship stations, the applicant must propose frequencies and ensure that those requested frequencies are consistent...

  19. 47 CFR 87.349 - Frequencies.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Frequencies. 87.349 Section 87.349... Aeronautical Utility Mobile Stations § 87.349 Frequencies. (a) The frequency assigned to an aeronautical... frequency used by the control tower for ground traffic control or by the flight service station...

  20. 47 CFR 80.45 - Frequencies.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Frequencies. 80.45 Section 80.45... MARITIME SERVICES Applications and Licenses § 80.45 Frequencies. For applications other than ship stations, the applicant must propose frequencies and ensure that those requested frequencies are consistent...

  1. 47 CFR 24.129 - Frequencies.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 2 2012-10-01 2012-10-01 false Frequencies. 24.129 Section 24.129... SERVICES Narrowband PCS § 24.129 Frequencies. The following frequencies are available for narrowband PCS: (a) Eighteen frequencies are available for assignment on a nationwide basis as follows: (1) Seven...

  2. 47 CFR 74.161 - Frequency tolerances.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Frequency tolerances. 74.161 Section 74.161... Technical Operation and Operators § 74.161 Frequency tolerances. The departure of the carrier frequency or frequencies of an experimental broadcast station must not exceed the tolerance specified in the instrument...

  3. 47 CFR 87.351 - Frequency changes.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Frequency changes. 87.351 Section 87.351... Aeronautical Utility Mobile Stations § 87.351 Frequency changes. When the aeronautical utility frequency is... control of unicom frequency) the licensee must submit an application for modification to specify the...

  4. 47 CFR 87.287 - Frequencies.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Frequencies. 87.287 Section 87.287... Data Link Land Test Stations § 87.287 Frequencies. (a) The frequencies assignable to aircraft data link..., 136.925 MHz, 136.950 MHz, and 136.975 MHz. Interstitial frequencies separated by 8.33 kilohertz...

  5. 47 CFR 87.217 - Frequencies.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Frequencies. 87.217 Section 87.217... Aeronautical Advisory Stations (Unicoms) § 87.217 Frequencies. (a) Only one unicom frequency will be assigned at any one airport. Applicants must request a particular frequency, which will be taken...

  6. 47 CFR 74.661 - Frequency tolerance.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Frequency tolerance. 74.661 Section 74.661... Stations § 74.661 Frequency tolerance. Stations in this service shall maintain the carrier frequency of each authorized transmitter to within the following percentage of the assigned frequency....

  7. 47 CFR 87.449 - Frequencies.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Frequencies. 87.449 Section 87.449... Operational Fixed Stations § 87.449 Frequencies. The following frequencies in the 72-76 MHz band are... TV reception on Channels 4 and 5. These frequencies are shared with the Land Mobile and the...

  8. 47 CFR 80.45 - Frequencies.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Frequencies. 80.45 Section 80.45... MARITIME SERVICES Applications and Licenses § 80.45 Frequencies. For applications other than ship stations, the applicant must propose frequencies and ensure that those requested frequencies are consistent...

  9. 47 CFR 74.161 - Frequency tolerances.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Frequency tolerances. 74.161 Section 74.161... Technical Operation and Operators § 74.161 Frequency tolerances. The departure of the carrier frequency or frequencies of an experimental broadcast station must not exceed the tolerance specified in the instrument...

  10. 47 CFR 95.853 - Frequency segments.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Frequency segments. 95.853 Section 95.853... SERVICES 218-219 MHz Service Technical Standards § 95.853 Frequency segments. There are two frequency segments available for assignment to the 218-219 MHz Service in each service area. Frequency segment A...

  11. 47 CFR 95.853 - Frequency segments.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Frequency segments. 95.853 Section 95.853... SERVICES 218-219 MHz Service Technical Standards § 95.853 Frequency segments. There are two frequency segments available for assignment to the 218-219 MHz Service in each service area. Frequency segment A...

  12. 47 CFR 24.135 - Frequency stability.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Frequency stability. 24.135 Section 24.135... SERVICES Narrowband PCS § 24.135 Frequency stability. (a) The frequency stability of the transmitter shall be maintained within ±0.0001 percent (±1 ppm) of the center frequency over a temperature variation...

  13. 47 CFR 87.195 - Frequencies.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Frequencies. 87.195 Section 87.195... Aircraft Stations Emergency Locator Transmitters § 87.195 Frequencies. (a) ELTs transmit on the frequency 121.500 MHz, using A3E, A3X or NON emission. ELTs that transmit on the frequency 406.0-406.1 MHz...

  14. 47 CFR 74.802 - Frequency assignment.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Frequency assignment. 74.802 Section 74.802... Frequency assignment. (a) Frequencies within the following bands may be assigned for use by low power... MHz. All zones 113 km (70 miles) (c) Specific frequency operation is required when operating...

  15. 47 CFR 87.303 - Frequencies.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Frequencies. 87.303 Section 87.303... Flight Test Stations § 87.303 Frequencies. (a) These frequencies are available for assignment to flight....375 3 123.450 3 (b) These additional frequencies are available for assignment only to flight...

  16. 47 CFR 80.375 - Radiodetermination frequencies.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Radiodetermination frequencies. 80.375 Section... SERVICES STATIONS IN THE MARITIME SERVICES Frequencies Radiodetermination § 80.375 Radiodetermination frequencies. This section describes the carrier frequencies assignable to radiodetermination stations....

  17. 47 CFR 87.449 - Frequencies.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Frequencies. 87.449 Section 87.449... Operational Fixed Stations § 87.449 Frequencies. The following frequencies in the 72-76 MHz band are... TV reception on Channels 4 and 5. These frequencies are shared with the Land Mobile and the...

  18. 47 CFR 87.421 - Frequencies.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Frequencies. 87.421 Section 87.421... Airport Control Tower Stations § 87.421 Frequencies. The Commission will assign VHF frequencies after coordination with the FAA. Frequencies in the following bands are available to control towers and RCOs....

  19. 47 CFR 74.802 - Frequency assignment.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Frequency assignment. 74.802 Section 74.802... Frequency assignment. (a) Frequencies within the following bands may be assigned for use by low power... MHz. All zones 113 km (70 miles) (c) Specific frequency operation is required when operating...

  20. 47 CFR 80.375 - Radiodetermination frequencies.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Radiodetermination frequencies. 80.375 Section... SERVICES STATIONS IN THE MARITIME SERVICES Frequencies Radiodetermination § 80.375 Radiodetermination frequencies. This section describes the carrier frequencies assignable to radiodetermination stations....

  1. 47 CFR 74.103 - Frequency assignment.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Frequency assignment. 74.103 Section 74.103....103 Frequency assignment. (a) Frequencies allocated to broadcasting and the various categories of auxiliary stations, in the FCC's Table of Frequency Allocations (Part 2 of this chapter), may be...

  2. 47 CFR 80.375 - Radiodetermination frequencies.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Radiodetermination frequencies. 80.375 Section... SERVICES STATIONS IN THE MARITIME SERVICES Frequencies Radiodetermination § 80.375 Radiodetermination frequencies. This section describes the carrier frequencies assignable to radiodetermination stations....

  3. 47 CFR 74.503 - Frequency selection.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Frequency selection. 74.503 Section 74.503... § 74.503 Frequency selection. (a) Each application for a new station or change in an existing station shall be specific with regard to frequency. In general, the lowest suitable frequency will be...

  4. 47 CFR 74.161 - Frequency tolerances.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Frequency tolerances. 74.161 Section 74.161... Technical Operation and Operators § 74.161 Frequency tolerances. The departure of the carrier frequency or frequencies of an experimental broadcast station must not exceed the tolerance specified in the instrument...

  5. 47 CFR 24.235 - Frequency stability.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 2 2013-10-01 2013-10-01 false Frequency stability. 24.235 Section 24.235... SERVICES Broadband PCS § 24.235 Frequency stability. The frequency stability shall be sufficient to ensure that the fundamental emission stays within the authorized frequency block....

  6. 47 CFR 80.375 - Radiodetermination frequencies.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Radiodetermination frequencies. 80.375 Section... SERVICES STATIONS IN THE MARITIME SERVICES Frequencies Radiodetermination § 80.375 Radiodetermination frequencies. This section describes the carrier frequencies assignable to radiodetermination stations....

  7. 47 CFR 24.229 - Frequencies.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 2 2013-10-01 2013-10-01 false Frequencies. 24.229 Section 24.229... SERVICES Broadband PCS § 24.229 Frequencies. The frequencies available in the Broadband PCS service are listed in this section in accordance with the frequency allocations table of § 2.106 of this chapter....

  8. 47 CFR 73.754 - Frequency monitors.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Frequency monitors. 73.754 Section 73.754... International Broadcast Stations § 73.754 Frequency monitors. (a) The licensee of each international broadcast station shall operate a frequency monitor at the transmitter independent of the frequency control of...

  9. 47 CFR 95.1113 - Frequency coordinator.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Frequency coordinator. 95.1113 Section 95.1113... SERVICES Wireless Medical Telemetry Service (WMTS) General Provisions § 95.1113 Frequency coordinator. (a) The Commission will designate a frequency coordinator(s) to manage the usage of the frequency...

  10. 47 CFR 74.103 - Frequency assignment.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Frequency assignment. 74.103 Section 74.103....103 Frequency assignment. (a) Frequencies allocated to broadcasting and the various categories of auxiliary stations, in the FCC's Table of Frequency Allocations (Part 2 of this chapter), may be...

  11. 47 CFR 5.303 - Frequencies.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 1 2014-10-01 2014-10-01 false Frequencies. 5.303 Section 5.303... Licenses § 5.303 Frequencies. Licensees may operate in any frequency band, except for the following: (a) Frequency bands at or below 38.6 GHz that are designated as restricted in § 15.205(a) of this chapter;...

  12. 47 CFR 87.217 - Frequencies.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Frequencies. 87.217 Section 87.217... Aeronautical Advisory Stations (Unicoms) § 87.217 Frequencies. (a) Only one unicom frequency will be assigned at any one airport. Applicants must request a particular frequency, which will be taken...

  13. 47 CFR 74.1261 - Frequency tolerance.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Frequency tolerance. 74.1261 Section 74.1261... FM Broadcast Booster Stations § 74.1261 Frequency tolerance. (a) The licensee of an FM translator or... frequency at the output of the translator within 0.01 percent of its assigned frequency. (b) The licensee...

  14. 47 CFR 74.1261 - Frequency tolerance.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Frequency tolerance. 74.1261 Section 74.1261... FM Broadcast Booster Stations § 74.1261 Frequency tolerance. (a) The licensee of an FM translator or... frequency at the output of the translator within 0.01 percent of its assigned frequency. (b) The licensee...

  15. 47 CFR 74.802 - Frequency assignment.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false Frequency assignment. 74.802 Section 74.802... Frequency assignment. (a) Frequencies within the following bands may be assigned for use by low power... MHz. All zones 113 km (70 miles) (c) Specific frequency operation is required when operating...

  16. 47 CFR 87.351 - Frequency changes.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Frequency changes. 87.351 Section 87.351... Aeronautical Utility Mobile Stations § 87.351 Frequency changes. When the aeronautical utility frequency is... control of unicom frequency) the licensee must submit an application for modification to specify the...

  17. 47 CFR 87.421 - Frequencies.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Frequencies. 87.421 Section 87.421... Airport Control Tower Stations § 87.421 Frequencies. The Commission will assign VHF frequencies after coordination with the FAA. Frequencies in the following bands are available to control towers and RCOs....

  18. 47 CFR 87.449 - Frequencies.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Frequencies. 87.449 Section 87.449... Operational Fixed Stations § 87.449 Frequencies. The following frequencies in the 72-76 MHz band are... TV reception on Channels 4 and 5. These frequencies are shared with the Land Mobile and the...

  19. 47 CFR 74.661 - Frequency tolerance.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false Frequency tolerance. 74.661 Section 74.661... Stations § 74.661 Frequency tolerance. Stations in this service shall maintain the carrier frequency of each authorized transmitter to within the following percentage of the assigned frequency....

  20. 47 CFR 87.351 - Frequency changes.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Frequency changes. 87.351 Section 87.351... Aeronautical Utility Mobile Stations § 87.351 Frequency changes. When the aeronautical utility frequency is... control of unicom frequency) the licensee must submit an application for modification to specify the...

  1. 47 CFR 87.349 - Frequencies.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Frequencies. 87.349 Section 87.349... Aeronautical Utility Mobile Stations § 87.349 Frequencies. (a) The frequency assigned to an aeronautical... frequency used by the control tower for ground traffic control or by the flight service station...

  2. 47 CFR 87.303 - Frequencies.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Frequencies. 87.303 Section 87.303... Flight Test Stations § 87.303 Frequencies. (a) These frequencies are available for assignment to flight....375 3 123.450 3 (b) These additional frequencies are available for assignment only to flight...

  3. 47 CFR 101.507 - Frequency stability.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Frequency stability. 101.507 Section 101.507... SERVICES 24 GHz Service and Digital Electronic Message Service § 101.507 Frequency stability. The frequency...% for each DEMS User Station transmitter. The frequency stability in the 24,250-25,250 MHz bands must...

  4. 47 CFR 87.303 - Frequencies.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Frequencies. 87.303 Section 87.303... Flight Test Stations § 87.303 Frequencies. (a) These frequencies are available for assignment to flight....375 3 123.450 3 (b) These additional frequencies are available for assignment only to flight...

  5. 47 CFR 74.561 - Frequency tolerance.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false Frequency tolerance. 74.561 Section 74.561... § 74.561 Frequency tolerance. In the bands above 944 MHz, the operating frequency of the transmitter shall be maintained in accordance with the following table: Frequency band (MHz) Tolerance as...

  6. 47 CFR 87.421 - Frequencies.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Frequencies. 87.421 Section 87.421... Airport Control Tower Stations § 87.421 Frequencies. The Commission will assign VHF frequencies after coordination with the FAA. Frequencies in the following bands are available to control towers and RCOs....

  7. 47 CFR 74.561 - Frequency tolerance.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Frequency tolerance. 74.561 Section 74.561... § 74.561 Frequency tolerance. In the bands above 944 MHz, the operating frequency of the transmitter shall be maintained in accordance with the following table: Frequency band (MHz) Tolerance as...

  8. 47 CFR 24.235 - Frequency stability.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Frequency stability. 24.235 Section 24.235... SERVICES Broadband PCS § 24.235 Frequency stability. The frequency stability shall be sufficient to ensure that the fundamental emission stays within the authorized frequency block....

  9. 47 CFR 87.349 - Frequencies.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Frequencies. 87.349 Section 87.349... Aeronautical Utility Mobile Stations § 87.349 Frequencies. (a) The frequency assigned to an aeronautical... frequency used by the control tower for ground traffic control or by the flight service station...

  10. 47 CFR 24.135 - Frequency stability.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 2 2014-10-01 2014-10-01 false Frequency stability. 24.135 Section 24.135... SERVICES Narrowband PCS § 24.135 Frequency stability. (a) The frequency stability of the transmitter shall be maintained within ±0.0001 percent (±1 ppm) of the center frequency over a temperature variation...

  11. 47 CFR 87.303 - Frequencies.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Frequencies. 87.303 Section 87.303... Flight Test Stations § 87.303 Frequencies. (a) These frequencies are available for assignment to flight....375 3 123.450 3 (b) These additional frequencies are available for assignment only to flight...

  12. 47 CFR 74.1261 - Frequency tolerance.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Frequency tolerance. 74.1261 Section 74.1261... FM Broadcast Booster Stations § 74.1261 Frequency tolerance. (a) The licensee of an FM translator or... frequency at the output of the translator within 0.01 percent of its assigned frequency. (b) The licensee...

  13. 47 CFR 24.135 - Frequency stability.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 2 2011-10-01 2011-10-01 false Frequency stability. 24.135 Section 24.135... SERVICES Narrowband PCS § 24.135 Frequency stability. (a) The frequency stability of the transmitter shall be maintained within ±0.0001 percent (±1 ppm) of the center frequency over a temperature variation...

  14. 47 CFR 24.135 - Frequency stability.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 2 2012-10-01 2012-10-01 false Frequency stability. 24.135 Section 24.135... SERVICES Narrowband PCS § 24.135 Frequency stability. (a) The frequency stability of the transmitter shall be maintained within ±0.0001 percent (±1 ppm) of the center frequency over a temperature variation...

  15. 47 CFR 24.229 - Frequencies.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 2 2011-10-01 2011-10-01 false Frequencies. 24.229 Section 24.229... SERVICES Broadband PCS § 24.229 Frequencies. The frequencies available in the Broadband PCS service are listed in this section in accordance with the frequency allocations table of § 2.106 of this chapter....

  16. 47 CFR 24.135 - Frequency stability.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 2 2013-10-01 2013-10-01 false Frequency stability. 24.135 Section 24.135... SERVICES Narrowband PCS § 24.135 Frequency stability. (a) The frequency stability of the transmitter shall be maintained within ±0.0001 percent (±1 ppm) of the center frequency over a temperature variation...

  17. 47 CFR 101.507 - Frequency stability.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Frequency stability. 101.507 Section 101.507... SERVICES 24 GHz Service and Digital Electronic Message Service § 101.507 Frequency stability. The frequency...% for each DEMS User Station transmitter. The frequency stability in the 24,250-25,250 MHz bands must...

  18. 47 CFR 74.503 - Frequency selection.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Frequency selection. 74.503 Section 74.503... § 74.503 Frequency selection. (a) Each application for a new station or change in an existing station shall be specific with regard to frequency. In general, the lowest suitable frequency will be...

  19. 47 CFR 24.129 - Frequencies.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 2 2013-10-01 2013-10-01 false Frequencies. 24.129 Section 24.129... SERVICES Narrowband PCS § 24.129 Frequencies. The following frequencies are available for narrowband PCS: (a) Eighteen frequencies are available for assignment on a nationwide basis as follows: (1) Seven...

  20. 47 CFR 73.754 - Frequency monitors.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Frequency monitors. 73.754 Section 73.754... International Broadcast Stations § 73.754 Frequency monitors. (a) The licensee of each international broadcast station shall operate a frequency monitor at the transmitter independent of the frequency control of...