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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. 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)

  3. Methods for estimating selected low-flow frequency statistics for unregulated streams in Kentucky

    USGS Publications Warehouse

    Martin, Gary R.; Arihood, Leslie D.

    2010-01-01

    This report provides estimates of, and presents methods for estimating, selected low-flow frequency statistics for unregulated streams in Kentucky including the 30-day mean low flows for recurrence intervals of 2 and 5 years (30Q2 and 30Q5) and the 7-day mean low flows for recurrence intervals of 5, 10, and 20 years (7Q2, 7Q10, and 7Q20). Estimates of these statistics are provided for 121 U.S. Geological Survey streamflow-gaging stations with data through the 2006 climate year, which is the 12-month period ending March 31 of each year. Data were screened to identify the periods of homogeneous, unregulated flows for use in the analyses. Logistic-regression equations are presented for estimating the annual probability of the selected low-flow frequency statistics being equal to zero. Weighted-least-squares regression equations were developed for estimating the magnitude of the nonzero 30Q2, 30Q5, 7Q2, 7Q10, and 7Q20 low flows. Three low-flow regions were defined for estimating the 7-day low-flow frequency statistics. The explicit explanatory variables in the regression equations include total drainage area and the mapped streamflow-variability index measured from a revised statewide coverage of this characteristic. The percentage of the station low-flow statistics correctly classified as zero or nonzero by use of the logistic-regression equations ranged from 87.5 to 93.8 percent. The average standard errors of prediction of the weighted-least-squares regression equations ranged from 108 to 226 percent. The 30Q2 regression equations have the smallest standard errors of prediction, and the 7Q20 regression equations have the largest standard errors of prediction. The regression equations are applicable only to stream sites with low flows unaffected by regulation from reservoirs and local diversions of flow and to drainage basins in specified ranges of basin characteristics. Caution is advised when applying the equations for basins with characteristics near the

  4. 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.

  5. Selected low-flow frequency statistics for continuous-record streamgage locations in Maryland, 2010

    USGS Publications Warehouse

    Doheny, Edward J.; Banks, William S.L.

    2010-01-01

    According to a 2008 report by the Governor's Advisory Committee on the Management and Protection of the State's Water Resources, Maryland's population grew by 35 percent between 1970 and 2000, and is expected to increase by an additional 27 percent between 2000 and 2030. Because domestic water demand generally increases in proportion to population growth, Maryland will be facing increased pressure on water resources over the next 20 years. Water-resources decisions should be based on sound, comprehensive, long-term data and low-flow frequency statistics from all available streamgage locations with unregulated streamflow and adequate record lengths. To provide the Maryland Department of the Environment with tools for making future water-resources decisions, the U.S. Geological Survey initiated a study in October 2009 to compute low-flow frequency statistics for selected streamgage locations in Maryland with 10 or more years of continuous streamflow records. This report presents low-flow frequency statistics for 114 continuous-record streamgage locations in Maryland. The computed statistics presented for each streamgage location include the mean 7-, 14-, and 30-consecutive day minimum daily low-flow dischages for recurrence intervals of 2, 10, and 20 years, and are based on approved streamflow records that include a minimum of 10 complete climatic years of record as of June 2010. Descriptive information for each of these streamgage locations, including the station number, station name, latitude, longitude, county, physiographic province, and drainage area, also is presented. The statistics are planned for incorporation into StreamStats, which is a U.S. Geological Survey Web application for obtaining stream information, and is being used by water-resource managers and decision makers in Maryland to address water-supply planning and management, water-use appropriation and permitting, wastewater and industrial discharge permitting, and setting minimum required

  6. Magnitude and frequency of low flows in the Suwannee River Water Management District, Florida

    USGS Publications Warehouse

    Giese, G.L.; Franklin, M.A.

    1996-01-01

    Low-flow frequency statistics for 20 gaging stations having at least 10 years of continuous record and 31 other stations having less than 10 years of continu ous record or a series of at least two low- flow measurements are presented for unregulated streams in the Suwannee River Water Management District in north-central Florida. Statistics for the 20 continuous-record stations included are the annual and monthly minimum consecutive-day average low- flow magnitudes for 1, 3, 7, 14, and 30 consecutive days for recurrence intervals of 2, 5, 10, 20, and, for some long-term stations, 50 years, based on records available through the 1994 climatic year.Only theannual statistics are given for the 31 other stations; these are for the 7- and 30-consecutive day periods only and for recurrence intervals of 2 and 10 years only. Annual low-flow frequency statistics range from zero for many small streams to 5,500 cubic feet per second for the annual 30- consecutive-day average flow with a recurrenceinterval of 2 years for the Suwannee River near Wilcox (station 02323500). Monthly low-flow frequency statistics range from zero for many small streams to 13,800 cubic feet per second for the minimum 30-consecutive-day average flow with a 2-year recurrence interval for the month of March for the same station. Generally, low-flow characteristics of streams in the Suwannee River Water Management District are controlled by climatic, topographic, and geologic fac tors. The carbonate Floridan aquifer system underlies, or is at the surface of, the entire District. The terrane's karstic nature results in manysinkholes and springs. In some places, springs may contribute greatly to low streamflow and the contributing areas of such springs may include areasoutside the presumed surface drainage area of the springs. In other places, water may enter sinkholes within a drainage basin, then reappear in springs downstream from a gage. Many of the smaller streams in the District go dry or have no flow

  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.

    2016-09-06

    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. Forecast-informed low-flow frequency analysis in a Bayesian framework for the northeastern United States

    NASA Astrophysics Data System (ADS)

    Steinschneider, Scott; Brown, Casey

    2012-10-01

    Structured variation in the frequency spectrum of critical hydrologic variables can have important implications for the design and management of water resources infrastructure, yet traditional hydrologic frequency analysis often ignores the influence of exogenous factors that can both precede and exert control over hydrologic responses. Moreover, emerging literature that has addressed predictable low-frequency oscillations in the probabilistic nature of hydrologic variables has focused almost exclusively on flood flows. This study explores a new approach for conditioning the frequency spectrum of hydrologic extremes on seasonal predictors and applies the method to annual minimum 7 day low flows, a critical low-flow statistic often utilized in water quality management and planning. A semiparametric local likelihood method is used to condition quantile estimates of the 7 day low flow on year-to-year hydroclimatic forecasts for two major rivers in the northeast United States. The local likelihood approach is employed in a Bayesian framework in which regional information is used to inform prior distributions of model parameters. The method is compared against a baseline approach that applies a static Bayesian inference with noninformative priors to derive unconditional parameter and quantile estimates. The implications of the approach for the efficacy of water quality regulations and as an adaptation to climate change are discussed.

  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. Estimating the magnitude and frequency of low flows of streams in Massachusetts

    USGS Publications Warehouse

    Risley, J.C.

    1994-01-01

    The report presents techniques used for estimating 7-day 2-year (7Q2) and 7-day 10-year (7Q10) flows at continuous-record streamflow-gaging stations, partial-record stations, and ungaged sites on streams in Massachusetts. A two-parameter log-normal probability distribution was used to compute low flows at 31 continuous-record stream-flow-gaging stations. Graphical and mathematical techniques were used to estimate low flows at partial-record stations. Regional regression techniques commonly are used to estimate 7Q2 and 7Q10 flows at ungaged stream sites. The development and application of a low-flow regression model is described. The model contains two parameters, mean and standard deviation, computed from separate regression equations that use total drainage area and basin relief as independent variables. The coefficients of determination of the mean and standard deviation regression equations are 0.964 and 0.960, respec- tively; the percentage of standard error of the regression of each equation are 35 and 34, respec- tively. The model is applicable for basins in Massachusetts having a drainage area of 5 to 150 square miles, a slope of less than 4 percent, and an area of stratified drift greater than 4 percent of the total drainage area. A computer program is presented that can be used to compute 7Q2 and 7Q10 flows and the 95-percent intervals of confidence and prediction for a given basin.

  14. Methods for estimating selected low-flow frequency statistics and harmonic mean flows for streams in Iowa

    USGS Publications Warehouse

    Eash, David A.; Barnes, Kimberlee K.

    2012-01-01

    A statewide study was conducted to develop regression equations for estimating six selected low-flow frequency statistics and harmonic mean flows for ungaged stream sites in Iowa. The estimation equations developed for the six low-flow frequency statistics include: the annual 1-, 7-, and 30-day mean low flows for a recurrence interval of 10 years, the annual 30-day mean low flow for a recurrence interval of 5 years, and the seasonal (October 1 through December 31) 1- and 7-day mean low flows for a recurrence interval of 10 years. Estimation equations also were developed for the harmonic-mean-flow statistic. Estimates of these seven selected statistics are provided for 208 U.S. Geological Survey continuous-record streamgages using data through September 30, 2006. The study area comprises streamgages located within Iowa and 50 miles beyond the State's borders. Because trend analyses indicated statistically significant positive trends when considering the entire period of record for the majority of the streamgages, the longest, most recent period of record without a significant trend was determined for each streamgage for use in the study. The median number of years of record used to compute each of these seven selected statistics was 35. Geographic information system software was used to measure 54 selected basin characteristics for each streamgage. Following the removal of two streamgages from the initial data set, data collected for 206 streamgages were compiled to investigate three approaches for regionalization of the seven selected statistics. Regionalization, a process using statistical regression analysis, provides a relation for efficiently transferring information from a group of streamgages in a region to ungaged sites in the region. The three regionalization approaches tested included statewide, regional, and region-of-influence regressions. For the regional regression, the study area was divided into three low-flow regions on the basis of hydrologic

  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 Broad River basin through March 2008

    USGS Publications Warehouse

    Guimaraes, Wladmir B.; Feaster, Toby D.

    2010-01-01

    Of the 23 streamgaging stations for which recurrence interval computations were made, 14 had low-flow statistics that were published in previous U.S. Geological Survey reports. A comparison of the low-flow statistics for the minimum mean flow for a 7-consecutive-day period with a 10-year recurrence interval (7Q10) from this study with the most recently published values indicated that 8 of the 14 streamgaging stations had values that were within plus or minus 25 percent of the previous value. Ten of the 14 streamgaging stations had negative percent differences indicating the low-flow statistic had decreased since the previous study, and 4 streamgaging stations had positive percent differences indicating that the low-flow statistic had increased since the previous study. The low-flow statistics are influenced by length of record, hydrologic regime under which the record was collected, techniques used to do the analysis, and other changes, such as urbanization, diversions, and so on, that may have occurred in the basin.

  17. Regional regression equations for the estimation of selected monthly low-flow duration and frequency statistics at ungaged sites on streams in New Jersey

    USGS Publications Warehouse

    Watson, Kara M.; McHugh, Amy R.

    2014-01-01

    Regional regression equations were developed for estimating monthly flow-duration and monthly low-flow frequency statistics for ungaged streams in Coastal Plain and non-coastal regions of New Jersey for baseline and current land- and water-use conditions. The equations were developed to estimate 87 different streamflow statistics, which include the monthly 99-, 90-, 85-, 75-, 50-, and 25-percentile flow-durations of the minimum 1-day daily flow; the August–September 99-, 90-, and 75-percentile minimum 1-day daily flow; and the monthly 7-day, 10-year (M7D10Y) low-flow frequency. These 87 streamflow statistics were computed for 41 continuous-record streamflow-gaging stations (streamgages) with 20 or more years of record and 167 low-flow partial-record stations in New Jersey with 10 or more streamflow measurements. The regression analyses used to develop equations to estimate selected streamflow statistics were performed by testing the relation between flow-duration statistics and low-flow frequency statistics for 32 basin characteristics (physical characteristics, land use, surficial geology, and climate) at the 41 streamgages and 167 low-flow partial-record stations. The regression analyses determined drainage area, soil permeability, average April precipitation, average June precipitation, and percent storage (water bodies and wetlands) were the significant explanatory variables for estimating the selected flow-duration and low-flow frequency statistics. Streamflow estimates were computed for two land- and water-use conditions in New Jersey—land- and water-use during the baseline period of record (defined as the years a streamgage had little to no change in development and water use) and current land- and water-use conditions (1989–2008)—for each selected station using data collected through water year 2008. The baseline period of record is representative of a period when the basin was unaffected by change in development. The current period is

  18. Methods for estimating selected spring and fall low-flow frequency statistics for ungaged stream sites in Iowa, based on data through June 2014

    USGS Publications Warehouse

    Eash, David A.; Barnes, Kimberlee K.; O'Shea, Padraic S.

    2016-09-19

    A statewide study was led to develop regression equations for estimating three selected spring and three selected fall low-flow frequency statistics for ungaged stream sites in Iowa. The estimation equations developed for the six low-flow frequency statistics include spring (April through June) 1-, 7-, and 30-day mean low flows for a recurrence interval of 10 years and fall (October through December) 1-, 7-, and 30-day mean low flows for a recurrence interval of 10 years. Estimates of the three selected spring statistics are provided for 241 U.S. Geological Survey continuous-record streamgages, and estimates of the three selected fall statistics are provided for 238 of these streamgages, using data through June 2014. Because only 9 years of fall streamflow record were available, three streamgages included in the development of the spring regression equations were not included in the development of the fall regression equations. Because of regulation, diversion, or urbanization, 30 of the 241 streamgages were not included in the development of the regression equations. The study area includes Iowa and adjacent areas within 50 miles of the Iowa border. Because trend analyses indicated statistically significant positive trends when considering the period of record for most of the streamgages, the longest, most recent period of record without a significant trend was determined for each streamgage for use in the study. Geographic information system software was used to measure 63 selected basin characteristics for each of the 211streamgages used to develop the regional regression equations. The study area was divided into three low-flow regions that were defined in a previous study for the development of regional regression equations.Because several streamgages included in the development of regional regression equations have estimates of zero flow calculated from observed streamflow for selected spring and fall low-flow frequency statistics, the final equations for the

  19. 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

  20. Estimating Low-Flow Frequency Statistics and Hydrologic Analysis of Selected Streamflow-Gaging Stations, Nooksack River Basin, Northwestern Washington and Canada

    USGS Publications Warehouse

    Curran, Christopher A.; Olsen, Theresa D.

    2009-01-01

    Low-flow frequency statistics were computed at 17 continuous-record streamflow-gaging stations and 8 miscellaneous measurement sites in and near the Nooksack River basin in northwestern Washington and Canada, including the 1, 3, 7, 15, 30, and 60 consecutive-day low flows with recurrence intervals of 2 and 10 years. Using these low-flow statistics, 12 regional regression equations were developed for estimating the same low-flow statistics at ungaged sites in the Nooksack River basin using a weighted-least-squares method. Adjusted R2 (coefficient of determination) values for the equations ranged from 0.79 to 0.93 and the root-mean-squared error (RMSE) expressed as a percentage ranged from 77 to 560 percent. Streamflow records from six gaging stations located in mountain-stream or lowland-stream subbasins of the Nooksack River basin were analyzed to determine if any of the gaging stations could be removed from the network without significant loss of information. Using methods of hydrograph comparison, daily-value correlation, variable space, and flow-duration ratios, and other factors relating to individual subbasins, the six gaging stations were prioritized from most to least important as follows: Skookum Creek (12209490), Anderson Creek (12210900), Warm Creek (12207750), Fishtrap Creek (12212050), Racehorse Creek (12206900), and Clearwater Creek (12207850). The optimum streamflow-gaging station network would contain all gaging stations except Clearwater Creek, and the minimum network would include Skookum Creek and Anderson Creek.

  1. Methods for estimating selected low-flow frequency statistics and mean annual flow for ungaged locations on streams in North Georgia

    USGS Publications Warehouse

    Gotvald, Anthony J.

    2017-01-13

    The U.S. Geological Survey, in cooperation with the Georgia Department of Natural Resources, Environmental Protection Division, developed regional regression equations for estimating selected low-flow frequency and mean annual flow statistics for ungaged streams in north Georgia that are not substantially affected by regulation, diversions, or urbanization. Selected low-flow frequency statistics and basin characteristics for 56 streamgage locations within north Georgia and 75 miles beyond the State’s borders in Alabama, Tennessee, North Carolina, and South Carolina were combined to form the final dataset used in the regional regression analysis. Because some of the streamgages in the study recorded zero flow, the final regression equations were developed using weighted left-censored regression analysis to analyze the flow data in an unbiased manner, with weights based on the number of years of record. The set of equations includes the annual minimum 1- and 7-day average streamflow with the 10-year recurrence interval (referred to as 1Q10 and 7Q10), monthly 7Q10, and mean annual flow. The final regional regression equations are functions of drainage area, mean annual precipitation, and relief ratio for the selected low-flow frequency statistics and drainage area and mean annual precipitation for mean annual flow. The average standard error of estimate was 13.7 percent for the mean annual flow regression equation and ranged from 26.1 to 91.6 percent for the selected low-flow frequency equations.The equations, which are based on data from streams with little to no flow alterations, can be used to provide estimates of the natural flows for selected ungaged stream locations in the area of Georgia north of the Fall Line. The regression equations are not to be used to estimate flows for streams that have been altered by the effects of major dams, surface-water withdrawals, groundwater withdrawals (pumping wells), diversions, or wastewater discharges. The regression

  2. Low-flow characteristics of Indiana streams

    USGS Publications Warehouse

    Stewart, J.A.

    1983-01-01

    Knowledge of low-flow data for Indiana streams is essential to the planners and developers of water resources for municipal, industrial, and recreational uses in the State. Low-flow data for 219 continuous-record gaging stations through the 1978 water year and for some stations since then are presented in tables and curves. Flow-duration and low-flow-frequency data were estimated or determined for continuous-record stations having more than 10 years of record. In addition, low-flow-frequency data were estimated for 248 partial-record stations. Methods for estimating these data are included in the report. (USGS)

  3. 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.

    2016-07-14

    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

  4. Low-flow characteristics of Indiana streams

    USGS Publications Warehouse

    Fowler, K.K.; Wilson, J.T.

    1996-01-01

    Knowledge of low-flow characteristics of streams is essential for management of water resources. Low-flow characteristics are presented for 229 continuous-record, streamflow-gaging stations and 285 partial-record stations in Indiana. Low- flow-frequency characteristics were computed for 210 continuous-record stations that had at least 10 years of record, and flow-duration curves were computed for all continuous-record stations. Low-flow-frequency and flow-duration analyses are based on available streamflow records through September 1993. Selected low-flow-frequency curves were computed for annual low flows and seasonal low flows. The four seasons are represented by the 3-month groups of March-May, June-August, September-November, and December- February. The 7-day, 10-year and the 7-day, 2 year low flows were estimated for 285 partial-record stations, which are ungaged sites where streamflow measurements were made at base flow. The same low-flow characteristics were estimated for 19 continuous-record stations where less than 10 years of record were available. Precipitation and geology directly influence the streams in Indiana. Streams in the northern, glaciated part of the State tend to have higher sustained base flows than those in the nonglaciated southern part. Flow at several of the continuous-record gaging stations is affected by some form of regulation or diversion. Low-flow characteristics for continuous-record stations at which flow is affected by regulation are determined using the period of record affected by regulation; natural flows prior to regulation are not used.

  5. Low-flow characteristics of Florida streams

    USGS Publications Warehouse

    Rumenik, R.P.

    1996-01-01

    Knowledge of the low-flow characteristics of Florida streams and rivers is essential in planning for the availability of adequate quantities of water for commercial- and public-water supply, agricultural irrigation, artificial recharge, and the dilution of waste discharge. This report provides low-flow characteristics for 216 continuous-record gaging stations using frequency analysis techniques. Included are low-flow frequency characteristics for 143 unregulated, gaging stations; and sample percentiles for 32 stations that were subject to regulation or diversion, and sample percentiles for 41 stations, regulated and unregulated, that exhibited significant trends in the annual low-flow time series. Estimates of low-flow frequency characteristics are provided for 242 partial-record stations and miscellaneous sites based on correlations with daily mean discharges at continuous-record stations. Low-flow measurement data are available at approximately 1,300 continuous-record gaging stations, partial- record stations and miscellaneous sites. Historic low-flow measurement data are accessible through the U.S. Geological Survey Automatic Data Processing System.

  6. Low-flow frequency and flow duration of selected South Carolina streams in the Catawba-Wateree and Santee River Basins through March 2012

    USGS Publications Warehouse

    Feaster, Toby D.; Guimaraes, Wladmir B.

    2014-01-01

    Part of the mission of both 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 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 11 selected streamgaging stations in the Catawba-Wateree and Santee River Basins in South Carolina and 2 in North Carolina. For five of the streamgaging stations, low-flow statistics include daily mean flow durations or 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. For the other eight streamgaging stations, only daily mean flow durations and (or) exceedance percentiles of annual minimum 7-day average flows are provided due to regulation. In either case, the low-flow statistics were computed from records available through March 31, 2012. Of the five streamgaging stations for which recurrence interval computations were made, three streamgaging stations in South Carolina were compared to low-flow statistics that were published in previous U.S. Geological Survey reports. A comparison of the low-flow

  7. 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

  8. 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

  9. Low-Flow Characteristics and Regionalization of Low-Flow Characteristics for Selected Streams in Arkansas

    USGS Publications Warehouse

    Funkhouser, Jaysson E.; Eng, Ken; Moix, Matthew W.

    2008-01-01

    Water use in Arkansas has increased dramatically in recent years. Since 1990, the use of water for all purposes except power generation has increased 53 percent (4,004 cubic feet per second in 1990 to 6,113 cubic feet per second in 2005). The biggest users are agriculture (90 percent), municipal water supply (4 percent) and industrial supply (2 percent). As the population of the State continues to grow, so does the demand for the State's water resources. The low-flow characteristics of a stream ultimately affect its utilization by humans. Specific information on the low-flow characteristics of streams is essential to State water-management agencies such as the Arkansas Department of Environmental Quality, the Arkansas Natural Resources Commission, and the Arkansas Game and Fish Commission when dealing with problems related to irrigation, municipal and industrial water supplies, fish and wildlife conservation, and dilution of waste. Low-flow frequency data are of particular value to management agencies responsible for the development and management of the State's water resources. This report contains the low-flow characteristics for 70 active continuous-streamflow record gaging stations, 59 inactive continuous-streamflow record stations, and 101 partial-record gaging stations. These characteristics are the annual 7-day, 10-year low flow and the annual 7-day, 2-year low flow, and the seasonal, bimonthly, and monthly 7-day, 10-year low flow for the 129 active and inactive continuous-streamflow record and 101 partial-record gaging stations. Low-flow characteristics were computed on the basis of streamflow data for the period of record through September 2005 for the continuous-streamflow record and partial-record streamflow gaging stations. The low-flow characteristics of these continuous- and partial-record streamflow gaging stations were utilized in a regional regression analysis to produce equations for estimating the annual, seasonal, bimonthly, and monthly

  10. 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.

    2016-02-09

    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.

  11. Low-flow characteristics for selected streams in Indiana

    USGS Publications Warehouse

    Fowler, Kathleen K.; Wilson, John T.

    2015-01-01

    The management and availability of Indiana’s water resources increase in importance every year. Specifically, information on low-flow characteristics of streams is essential to State water-management agencies. These agencies need low-flow information when working with issues related to irrigation, municipal and industrial water supplies, fish and wildlife protection, and the dilution of waste. Industrial, municipal, and other facilities must obtain National Pollutant Discharge Elimination System (NPDES) permits if their discharges go directly to surface waters. The Indiana Department of Environmental Management (IDEM) requires low-flow statistics in order to administer the NPDES permit program. Low-flow-frequency characteristics were computed for 272 continuous-record stations. The information includes low-flow-frequency analysis, flow-duration analysis, and harmonic mean for the continuous-record stations. For those stations affected by some form of regulation, low-flow frequency curves are based on the longest period of homogeneous record under current conditions. Low-flow-frequency values and harmonic mean flow (if sufficient data were available) were estimated for the 166 partial-record stations. Partial-record stations are ungaged sites where streamflow measurements were made at base flow.

  12. Low-flow characteristics of streams West Virginia

    USGS Publications Warehouse

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

    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)

  13. 77 FR 17563 - Low Flow Protection Policy

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-26

    ... 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 Policy... approved the release of a proposed Low Flow Protection Policy for public review and comment. The Policy...

  14. Low flow vortex shedding flowmeter

    NASA Technical Reports Server (NTRS)

    Waugaman, Charles J.

    1989-01-01

    The purpose was to continue a development project on a no moving parts vortex shedding flowmeter used for flow measurement of hypergols. The project involved the design and construction of a test loop to evaluate the meter for flow of Freon which simulates the hypergol fluids. Results were obtained on the output frequency characteristics of the flow meter as a function of flow rate. A family of flow meters for larger size lines and ranges of flow was sized based on the results of the tested meter.

  15. 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

  16. LFSTAT - An R-Package for Low-Flow Analysis

    NASA Astrophysics Data System (ADS)

    Koffler, D.; Laaha, G.

    2012-04-01

    When analysing daily streamflow data focusing on low flow and drought, the state of the art is well documented in the Manual on Low-Flow Estimation and Prediction [1] published by the WMO. While it is clear what has to be done, it is not so clear how to preform the analysis and make the calculation as reproducible as possible. Our software solution expands the high preforming statistical open source software package R to analyse daily stream flow data 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) to analyse data in R. Functionality includes estimation of the most important low-flow indices. Beside standardly used flow indices also BFI and Recession constants can be computed. The main applications of L-moment based Extreme value analysis and regional frequency analysis (RFA) are available. Calculation of streamflow deficits is another important feature. The most common graphics are prepared and can easily be modified according to the users preferences. Graphics include hydrographs for different periods, flexible streamflow deficit plots, baseflow visualisation, flow duration curves as well as double mass curves just to name a few. The package uses a S3-class called lfobj (low-flow objects). Once this objects are created, analysis can be preformed by mouse-click, and a script can be saved to make the analysis easy reproducible. At the moment we are offering implementation of all major methods proposed in the WMO manual on Low-flow Estimation and Predictions. Future plans include e.g. report export in odt-file using odf-weave. We hope to offer a tool to ease and structure the analysis of stream flow data focusing on low-flows and to make analysis transparent and communicable. The package is designed for hydrological research and water management practice, but can also be used in teaching students the first steps in low-flow hydrology.

  17. An assessment of low flows in streams in northeastern Wyoming

    USGS Publications Warehouse

    Armentrout, G.W.; Wilson, J.F.

    1987-01-01

    Low flows were assessed and summarized in the following basins in northeastern Wyoming: Little Bighorn, Tongue, Powder, Little Missouri, Belle Fourche, Cheyenne, and Niobrara River, and about 200 river miles of the North Platte River and its tributaries. Only existing data from streamflow stations and miscellaneous observation sites during the period, 1930-80, were used. Data for a few stations in Montana and South Dakota were used in the analysis. Data were available for 56 perennial streams, 38 intermittent streams, and 34 ephemeral streams. The distribution of minimum observed flows of record at all stations and sites and the 7-day, 10-year low flows at mountain stations and main-stem plains stations are shown on a map. Seven day low flows were determined by fitting the log Pearsons Type III distribution to the data; results are tabulated only for the stations with at least 10 years of record that included at least one major drought. Most streams that originate in the foothills and plains have no flow during part of every year, and are typical of much of the study area. For stations on these streams , the frequency of the annual maximum number of consecutive days of no flow was determined, as an indicator of the likelihood of extended periods of no flow or drought. For estimates at ungaged sites on streams in the Bighorn Mountains only, a simple regression of 7-day, 10-year low flow on drainage area has a standard error of 64%, based on 19 stations with drainage areas of 2 to 200 sq mi. The 7-day, 10-year low flow in main-stem streams can be interpolated from graphs of 7-day, 10-year low flow versus distance along the main channel. Additional studies of low flow are needed. The data base, particularly synoptic baseflow information, needs considerable expansion. Also, the use of storage-analysis procedures should be considered as a means of assessing the availability of water in streams that otherwise are fully appropriated or that are ephemeral. (Author 's

  18. 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.

  19. Methods for estimating low-flow statistics for Massachusetts streams

    USGS Publications Warehouse

    Ries, Kernell G.; Friesz, Paul J.

    2000-01-01

    Methods and computer software are described in this report for determining flow duration, low-flow frequency statistics, and August median flows. These low-flow statistics can be estimated for unregulated streams in Massachusetts using different methods depending on whether the location of interest is at a streamgaging station, a low-flow partial-record station, or an ungaged site where no data are available. Low-flow statistics for streamgaging stations can be estimated using standard U.S. Geological Survey methods described in the report. The MOVE.1 mathematical method and a graphical correlation method can be used to estimate low-flow statistics for low-flow partial-record stations. The MOVE.1 method is recommended when the relation between measured flows at a partial-record station and daily mean flows at a nearby, hydrologically similar streamgaging station is linear, and the graphical method is recommended when the relation is curved. Equations are presented for computing the variance and equivalent years of record for estimates of low-flow statistics for low-flow partial-record stations when either a single or multiple index stations are used to determine the estimates. The drainage-area ratio method or regression equations can be used to estimate low-flow statistics for ungaged sites where no data are available. The drainage-area ratio method is generally as accurate as or more accurate than regression estimates when the drainage-area ratio for an ungaged site is between 0.3 and 1.5 times the drainage area of the index data-collection site. Regression equations were developed to estimate the natural, long-term 99-, 98-, 95-, 90-, 85-, 80-, 75-, 70-, 60-, and 50-percent duration flows; the 7-day, 2-year and the 7-day, 10-year low flows; and the August median flow for ungaged sites in Massachusetts. Streamflow statistics and basin characteristics for 87 to 133 streamgaging stations and low-flow partial-record stations were used to develop the equations. The

  20. Low-flow characteristics and discharge profiles for selected streams in the Neuse River basin, North Carolina

    USGS Publications Warehouse

    Weaver, J.C.

    1998-01-01

    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 50 continuous-record gaging stations and 113 partial-record measuring sites in the Neuse River Basin in North Carolina. Records of discharge collected through the 1996 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.

  1. Evolution of low flows in Czechia revisited

    NASA Astrophysics Data System (ADS)

    Ledvinka, O.

    2015-06-01

    Although a nationwide study focusing on the evolution of low flows in Czechia was conducted in the past, a need for the revision of the results has arisen. By means of the trend analysis, which specifically considers the presence of significant serial correlation at the first lag, the former study highlighted areas where 7-day low flows increase or decrease. However, taking into account only the lag-one autoregressive process might still have led to the detection of so-called pseudo-trends because, besides short-term persistence, also long-term persistence may adversely influence the variance of the test statistic when the independence among data is required. Therefore, one should carefully investigate the presence of persistence in time series. Before the trend analysis itself, the authors' previous studies aimed at the discrimination between short memory processes and long memory processes employing jointly the Phillips-Perron test and the Kwiatkowski-Phillips-Schmidt-Shin test. This analysis was accompanied by the Hurst exponent estimation. Here, the subsequent identification of trends is carried out using three modifications of the Mann-Kendall test that allow different kinds of persistence. These include the Bayley-Hammersley-Matalas-Langbein-Lettenmaier equivalent sample size approach, the trend-free pre-whitening approach and a block bootstrap with automatic selection of the block length, which was applied for the first time in hydrology. The general results are similar to those presented in the former study on trends. Nevertheless, the divergent minimum discharges evolution in the western part of Czechia is now much clear. Moreover, no significant increasing trend in series incorporating Julian days was found.

  2. Low-flow characteristics of streams in Ohio through water year 1997

    USGS Publications Warehouse

    Straub, David E.

    2001-01-01

    This report presents selected low-flow and flow-duration characteristics for 386 sites throughout Ohio. These sites include 195 long-term continuous-record stations with streamflow data through water year 1997 (October 1 to September 30) and for 191 low-flow partial-record stations with measurements into water year 1999. The characteristics presented for the long-term continuous-record stations are minimum daily streamflow; average daily streamflow; harmonic mean flow; 1-, 7-, 30-, and 90-day minimum average low flow with 2-, 5-, 10-, 20-, and 50-year recurrence intervals; and 98-, 95-, 90-, 85-, 80-, 75-, 70-, 60-, 50-, 40-, 30-, 20-, and 10-percent daily duration flows. The characteristics presented for the low-flow partial-record stations are minimum observed streamflow; estimated 1-, 7-, 30-, and 90-day minimum average low flow with 2-, 10-, and 20-year recurrence intervals; and estimated 98-, 95-, 90-, 85- and 80-percent daily duration flows. The low-flow frequency and duration analyses were done for three seasonal periods (warm weather, May 1 to November 30; winter, December 1 to February 28/29; and autumn, September 1 to November 30), plus the annual period based on the climatic year (April 1 to March 31).

  3. 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

  4. Methods for estimating low-flow characteristics of ungaged streams in selected areas, northern Florida

    USGS Publications Warehouse

    Rumenik, R.P.; Grubbs, J.W.

    1996-01-01

    Methods for estimating low-flow frequency characteristics at ungaged sites were developed for two areas in northern Florida. In the Yellow, Blackwater, Escambia, and Perdido River Basins study area (northwestern Florida), regional regression equations were developed for estimating the 7- and 30-day, 2- and 10-year low-flow characteristic (Q7,2, Q7,10, Q30,2, and Q30,10) by determining values of basin characteristics from digital Geographical Information System (GIS) coverages or hardcopy maps. A GIS, ARC-INFO, was used to quantify basin characteristics that were used in regression equations. Sources of digital data used in this analysis are elevation data, from a digital elevation model, stream length and location data from a digital hydrography coverage, and watershed boundaries digitized from topographic maps. The most accurate regression equations employed a basin characteristic that was based on a simple conceptual model of one- dimensional ground-water flow using Darcy's law. Slightly less accurate equations were obtained using drainage area as the only explanatory variable. The standard error of prediction for the Darcy and drainage area equations of Q7,2 was 65 and 74 percent, respectively; Q7,10, 58 and 62 percent, respectively; Q30,2, 51 and, 54 percent, respectively; and Q30,10, 44 and 51 percent, respectively. In the Santa Fe River Basin study area (northeastern Florida), a flow-routing method was used to estimate low-flow characteristics at ungaged sites from low stream- flow analyses based on records at gaged sites. The use of the flow-routing method is suggested for areas where regression analysis proves unsuccessful, where low-flow characteristics have been defined at a significant number of sites, and where information about the basin characteristics has been thoroughly researched. Low-flow frequency characteristics determined at 40 sites and measurements made during five synoptic runs in 1989-91 were used to develop a flow-routing method. Low-flow

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    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. 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 confirmed that many of the step changes and around half of the sites with an increasing trend were associated with regulation. Around a third of the sites with a decreasing trend were associated with a change of gauge datum. 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 most sites, the majority of low flows occur in one season in the late summer to autumn, as driven by the lower precipitation and higher evaporative demand in this season, but this is complicated

  6. Low-flow characteristics of streams in Maryland and Delaware

    USGS Publications Warehouse

    Carpenter, David H.; Hayes, Donald C.

    1996-01-01

    Hydrologic information on the variability of streamflow during low-flow periods is presented. At-site data on low-flow characteristics of streamflow under natural conditions are given for 94 continuous-record gaging stations in Maryland, Delaware, and surrounding States, and for 131 low-flow partial-record gaging stations in Maryland and Delaware. Equations and transfer methods are developed to estimate low-flow characteristics at ungaged stream sites in Maryland and Delaware for average 7-, 14-, and 30-consecutive-day low-flow discharges for recurrence intervals of 2, 10, and 20 years. Estimates of the accuracy of the methods are presented. Maryland and Delaware are divided into four regions on the basis of physiography and the results of regression analyses. Equations are developed from a generalized least-squares multiple regression technique to estimate low-flow characteristics for the Eastern Shore region, the eastern-Piedmont region, and the western region. Adjustments are necessary to low-flow discharges estimated from the equation for the western region because of the effects of carbonate rocks on low flows. An equation is developed on the basis of a distance-weighted average of low-flow discharges at gaging stations to estimate low-flow characteristics for the southern region. Two methods are developed for transferring low-flow characteristics to ungaged sites on gaged streams. One method transfers low-flow characteristics to an ungaged site either upstream or downstream from a gaging station and the other method transfers the characteristics to an ungaged site between gaging stations.

  7. Low-flow characteristics of streams in the Puget Sound region, Washington

    USGS Publications Warehouse

    Hidaka, F.T.

    1973-01-01

    Periods of low streamflow are usually the most critical factor in relation to most water uses. The purpose of this report is to present data on low-flow characteristics of streams in the Puget Sound region, Washington, and to briefly explain some of the factors that influence low flow in the various basins. Presented are data on low-flow frequencies of streams in the Puget Sound region, as gathered at 150 gaging stations. Four indexes were computed from the flow-flow-frequency curves and were used as a basis to compare the low-flow characteristics of the streams. The indexes are the (1) low-flow-yield index, expressed in unit runoff per square mile; (2) base-flow index, or the ratio of the median 7-day low flow to the average discharge; (3) slope index, or slope of annual 7-day low-flow-frequency curve; and (4) spacing index, or spread between the 7-day and 183-day low-flow-frequency curves. The indexes showed a wide variation between streams due to the complex interrelation between climate, topography, and geology. The largest low-flow-yield indexes determined--greater than 1.5 cfs (cubic feet per second) per square mile--were for streams that head at high altitudes in the Cascade and Olympic Mountains and have their sources at glaciers. The smallest low-flow-yield indexes--less than 0.5 cfs per square mile--were for the small streams that drain the lowlands adjacent to Puget Sound. Indexes between the two extremes were for nonglacial streams that head at fairly high altitudes in areas of abundant precipitation. The base-flow index has variations that can be attributed to a basin's hydrogeology, with very little influence from climate. The largest base-flow indexes were obtained for streams draining permeable unconsolidated glacial and alluvial sediments in parts of the lowlands adjacent to Puget Sound. Large volume of ground water in these materials sustain flows during late summer. The smallest indexes were computed for streams draining areas underlain by

  8. The importance of context dependency for understanding the effects of low flow events on fish

    USGS Publications Warehouse

    Walters, Annika W.

    2014-01-01

    The natural hydrology of streams and rivers has been extensively altered by dam construction, water diversion, and climate change. An increased frequency of low-flow events will affect fish by changing habitat availability, resource availability, and reproductive cues. I reviewed the literature to characterize the approaches taken to assess low-flow events and fish, the main effects of low-flow events on fish, and the associated mechanistic drivers. Most studies are focused on temperate streams and are comparative in nature. Decreased stream flow is associated with decreased survival, growth, and abundance of fish populations and shifts in community composition, but effects are variable. This variability in effects is probably caused by context dependence. I propose 3 main sources of context dependence that drive the variation in fish responses to low-flow events: attributes of the low-flow event, attributes of the habitat, and attributes of the fish. Awareness of these sources of context dependence can help managers interpret and explain data, predict vulnerability of fish communities, and prioritize appropriate management actions.

  9. 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.

  10. 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

  11. Low-flow characteristics and profiles for selected streams in the Roanoke River basin, North Carolina

    USGS Publications Warehouse

    Weaver, J.C.

    1996-01-01

    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 22 continuous-record gaging stations in North Carolina (19 sites) and Virginia (3 sites) and 60 partial-record gaging stations in the North Carolina Roanoke River Basin. Records of discharge collected through the 1994 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 that flow during November through March only is considered; and (5) 7Q2 low-flow discharge. The potential for sustaining base flows is moderate to high in the western part of the basin as well as in the eastern and western fringes of the Piedmont and Coastal Plain physiographic provinces, respectively. Areas of low potential for sustaining base flow exist in the central part of the basin (between eastern Caswell County and western Warren County), where soils have low infiltration rates, and in lower regions of the Coastal Plain, where small streams tend to have zero flow during prolonged drought. Drainage area and low-flow discharge profiles are presented for 10 streams in the Roanoke River Basin in North Carolina and reflect a wide range in basin size, characteristics, and streamflow conditions. The selected streams are Town Fork Creek, Hogans Creek, Mayo River, Buffalo Creek, Smith River, Country Line Creek, Dan River, Marlow Creek, Hyco River, and Roanoke River. The drainage-area profiles show the increases in drainage areas as streams travel their course in the basin. At the mouths of streams profiles, the drainage areas range from 22 miles to about 9,700 miles. Low-flow discharges for each stream

  12. Analyzing Drought From Paleo-Reconstructions Of 7-Day Low Flow In The Hudson River Basin

    NASA Astrophysics Data System (ADS)

    Zamora, M. R.; Cook, E.; Gelman, A.; Lall, U.

    2002-12-01

    The annual 7-day low flow in a stream is a measure of the dry season conditions in a stream. Consequently, it is a useful indicator for multi-year droughts. Here, we first present the application of a Generalized Linear Model in a Bayesian Hierarchical Modeling Framework for reconstructing the annual 7-day low flow series at 5 locations in the Hudson River Basin using 11 regional tree ring chronologies. This technique directly provides estimates of the posterior probability distribution of each reconstructed streamflow value, considering model parameter uncertainty. Given these reconstructions, we examine the frequency and recurrence attributes of extreme droughts in the region and their potential connections to known low frequency climate modes.

  13. Low-flow analysis with a conditional Weilbull tail model

    NASA Astrophysics Data System (ADS)

    Durrans, S. Rocky

    Estimates of low-flow quantiles, such as the 7-day, 10-year low flow, which are usually obtained by statistical modeling of observed data series, are widely used in water quality management. This paper presents a conditional modeling approach to low-flow analysis that employs only those data values which are less than or equal to a ceiling value. Modeling in this fashion has been motivated by the observation that annual low flows may derive from mixed processes and by the subjective nature of graphical methods, such as those employed by the U.S. Geological Survey, which are often employed in such cases. Results of Monte Carlo experiments demonstrate that the conditional modeling approach yields a low-flow quantile estimator whose bias and RMSE are comparable to more conventional modeling approaches of fitting a classical textbook probability distribution on the basis of all observed data values, even when the underlying population is of a ``well-behaved'' form. Since the complex forms of mixed low-flow data distributions are not capable of being represented by classical textbook distributions and since the conditional modeling approach performs comparably to those models even when the data derive from well-behaved probability distributions, these results imply that the conditional modeling approach is worthy of consideration for use by hydrologists. The conditional modeling approach also leads rather naturally to a scheme, much like that used in index flood methods, whereby a regional low-flow estimator might be devised. An application of the conditional modeling approach to 48 low-flow data series in Alabama is presented.

  14. 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

  15. 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.

  16. 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.

  17. 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...

  18. 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.

  19. Evaluation of low flow characteristics of the Vermont Yankee plant

    SciTech Connect

    Ganther, S.; LeFrancoi, M.; Bergeron, P.

    1997-12-01

    Boiling water reactor (BWR) core flow instrumentation inaccuracies under low-flow conditions have been the subject of both reactor vendor and regulatory communications in response to incidents of the reported core flow being less than the flow corresponding to the natural-circulation line on the power flow map. During single recirculation loop operation, low-flow conditions exist in the idle recirculation loop, and these flow inaccuracies can affect the usefulness of the reported core flow. Accurate core flow indications are needed above 25% power to administer fuel thermal limits and comply with restrictions associated with the potential for thermal-hydraulic instability. While the natural-circulation line on the power flow map is recognized to be a nominal estimate of the flow expected at and near natural-circulation conditions, the boundaries of the stability regions are associated with conditions assumed in safety analyses performed to demonstrate compliance with general design criteria 10 and 12.

  20. Chemical composition of streams during low flow; Fairfax County, Virginia

    USGS Publications Warehouse

    Larson, J.D.

    1978-01-01

    Water samples were collected and stream discharges were measured at 49 sites in Fairfax County, Virginia during a period of low flow in August 1977. In addition, pesticide and metal content of residue on stream-bottom sediments from several major streams in the county were analysed. Waters from the streams in Fairfax County have generally good chemical quality during low flow. One stream in Vienna, Virginia has a high sodium chloride content, suggesting an upstream discharge of salty water. Higher concentrations of dissolved, solids reflect both the effects of geology and urbanization. Streams draining Triassic rocks in the western section of the county are characterized by the greatest natural concentration of dissolved minerals in the water. The concentrations of pesticide and metal residue associated with bottom sediments suggest a low level of pollution in the streams. One site in western Fairfax County contained above-normal levels of polychlorinated biphenyls (PCB's) in the stream sediments.

  1. 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

  2. Monthly low-flow characteristics of Georgia streams

    USGS Publications Warehouse

    Carter, R.F.; Fanning, J.D.

    1982-01-01

    Statistics of monthly minimum flows are presented for 129 streamflow stations for each month of the year. Flow statistics provided are the log-Pearson Type III distribution. The probable magnitude of average standard errors due to time-sampling bias is tabulated. The average standard errors were found to be similar over a wide area comprising approximately the northern two-thirds of the State. In this area, the average standard error of estimate for a low-flow statistic with a recurrence interval of 20 years and estimated on the basis of 10 years of record is about 17%. In the southern third of the State, the average standard errors were found to lie in a narrow range, but were significantly greater than in the north. In the southern area, the average standard error of estimate for a low flow statistic with a recurrence interval of 20 years and estimated on the basis of 10 years of record is about 40%. (USGS)

  3. 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.

  4. 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.

  5. 77 FR 35464 - Extension of Comment Period-Proposed Low Flow Protection Policy

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-13

    ... 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 Protection... commissioners approved the release of the proposed Low Flow Protection Policy for public review and comment....

  6. Comparison of Methods for Estimating Low Flow Characteristics of Streams

    USGS Publications Warehouse

    Tasker, Gary D.

    1987-01-01

    Four methods for estimating the 7-day, 10-year and 7-day, 20-year low flows for streams are compared by the bootstrap method. The bootstrap method is a Monte Carlo technique in which random samples are drawn from an unspecified sampling distribution defined from observed data. The nonparametric nature of the bootstrap makes it suitable for comparing methods based on a flow series for which the true distribution is unknown. Results show that the two methods based on hypothetical distribution (Log-Pearson III and Weibull) had lower mean square errors than did the G. E. P. Box-D. R. Cox transformation method or the Log-W. C. Boughton method which is based on a fit of plotting positions.

  7. Low-flow operation and testing of pumps in nuclear plants

    SciTech Connect

    Greenstreet, W.L.

    1989-01-01

    Low-flow operation of centrifugal pumps introduces hydraulic instability and other factors that can cause damage to these machines. The resulting degradation has been studied and recorded for pumps in electric power plants. The objectives of this paper are to (1) describe the damage-producing phenomena, including their sources and consequences; (2) relate these observations to expectations for damage caused by low-flow operation of pumps in nuclear power plants; and (3) assess the utility of low-flow testing. Hydraulic behavior during low-flow operation is reviewed for a typical centrifugal pump stage, and the damage-producing mechanisms are described. Pump monitoring practices, in conjunction with pump performance characteristics, are considered; experience data are reviewed; and the effectiveness of low-flow surveillance monitoring is examined. Degradation caused by low-flow operation is shown to be an important factor, and low-flow surveillance testing is shown to be inadequate. 18 refs., 5 figs., 4 tabs.

  8. 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

    2016-04-19

    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.

  9. 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

  10. Contributions of collision rate and collision efficiency to erythrocyte aggregation in postcapillary venules at low flow rates.

    PubMed

    Kim, Sangho; Zhen, Janet; Popel, Aleksander S; Intaglietta, Marcos; Johnson, Paul C

    2007-09-01

    Red blood cell aggregation at low flow rates increases venous vascular resistance, but the process of aggregate formation in these vessels is not well understood. We previously reported that aggregate formation in postcapillary venules of the rat spinotrapezius muscle mainly occurs in a middle region between 15 and 30 microm downstream from the entrance. In light of the findings in that study, the main purpose of this study was to test two hypotheses by measuring collision frequency along the length of the venules during low flow. We tested the hypothesis that aggregation rarely occurs in the initial 15-microm region of the venule because collision frequency is very low. We found that collision frequency was lower than in other regions, but collision efficiency (the ratio of aggregate formation to collisions) was almost nil in this region, most likely because of entrance effects and time required for aggregation. Radial migration of red blood cells and Dextran 500 had no effect on collision frequency. We also tested the hypothesis that aggregation was reduced in the distal venule region because of the low aggregability of remaining nonaggregated cells. Our findings support this hypothesis, since a simple model based on the ratio of aggregatable to nonaggregatable red blood cells predicts the time course of collision efficiency in this region. Collision efficiency averaged 18% overall but varied from 0 to 52% and was highest in the middle region. We conclude that while collision frequency influences red blood cell aggregate formation in postcapillary venules, collision efficiency is more important.

  11. Summer low flows in New England during the 20th Century

    USGS Publications Warehouse

    Hodgkins, G.A.; Dudley, R.W.; Huntington, T.G.

    2005-01-01

    High springtime river flows came earlier by one to two weeks in large parts of northern New England during the 20th Century. In this study it was hypothesized that late spring/early summer recessional flows and late summer/early fall low flows could also be occurring earlier. This could result in a longer period of low flow recession and a decrease in the magnitude of low flows. To test this hypothesis, variations over time in the magnitude and timing of low flows were analyzed. To help understand the relation between low flows and climatic variables in New England, low flows were correlated with air temperatures and precipitation. Analysis of data from 23 rural, unregulated rivers across New England indicated little evidence of consistent changes in the timing or magnitude of late summer/early fall low flows during the 20th Century. The interannual variability in the timing and magnitude of the low flows in northern New England was explained much more by the interannual variability in precipitation than by the interannual variability of air temperatures. The highest correlation between the magnitude of the low flows and air temperatures was with May through November temperatures (r = -0.37, p = 0.0017), while the highest correlation with precipitation was with July through August precipitation (r = 0.67, p < 0.0001). (JAWRA) (Copyright ?? 2005).

  12. 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

  13. Reliable estimations of extreme low flows by integrating very low flows in the model performance evaluation with a multi-metric framework

    NASA Astrophysics Data System (ADS)

    Pfannerstill, Matthias; Guse, Björn; Fohrer, Nicola

    2014-05-01

    Hydrological models are helpful tools to predict hydrological extremes and to understand the main governing processes for flood and drought events. For reliable predictions of extremes in future simulation such as climate change estimations, a precise representation of high and low flows in hydrological models is required. As a consequence, the hydrological models have to be calibrated accurately to provide reasonable model results for the different phases of the hydrograph simultaneously. For this challenge, the different phases of the hydrograph have to be considered in multi-metric frameworks with appropriate performance metrics. Low flows need to be reproduced together with high flows without neglecting the other phases of the hydrograph. In our study, we highlight the relevance of model evaluation for very low and low flows with separate performance metrics to achieve a satisfying model performance for the low flow prediction together with the overall discharge reproduction. Therefore, we present a multi-metric evaluation framework to identify calibration runs with a precise representation of the hydrograph. In order to consider a fairly balanced evaluation between high and low flow phases, we divided the flow duration curve into segments of high, medium and low flow phases, and additionally into extreme high and extreme low flow phases. The model performance was evaluated stepwise for these segments separately with the root mean square error (RMSE) together with further application of the Nash-Sutcliffe efficiency and the percent bias for the whole discharge. Our results show that this evaluation method leads to an improved selection of model runs with enhanced overall model performance by the refined segmentation of FDC. By combining performance metrics for high flow conditions with low flow conditions, this study demonstrates the challenge of calibrating a model with a satisfactory performance in high and low phases simultaneously. Consequently, we conclude

  14. Selected low-flow frequency statistics for continuous-record streamgages in Georgia, 2013

    USGS Publications Warehouse

    Gotvald, Anthony J.

    2016-04-13

    This report presents the annual and monthly minimum 1- and 7-day average streamflows with the 10-year recurrence interval (1Q10 and 7Q10) for 197 continuous-record streamgages in Georgia. Streamgages used in the study included active and discontinued stations having a minimum of 10 complete climatic years of record as of September 30, 2013. The 1Q10 and 7Q10 flow statistics were computed for 85 streamgages on unregulated streams with minimal diversions upstream, 43 streamgages on regulated streams, and 69 streamgages known, or considered, to be affected by varying degrees of diversions upstream. Descriptive information for each of these streamgages, including the U.S. Geological Survey (USGS) station number, station name, latitude, longitude, county, drainage area, and period of record analyzed also is presented.Kendall’s tau nonparametric test was used to determine the statistical significance of trends in annual and monthly minimum 1-day and 7-day average flows for the 197 streamgages. Significant negative trends in the minimum annual 1-day and 7-day average streamflow were indicated for 77 of the 197 streamgages. Many of these significant negative trends are due to the period of record ending during one of the recent droughts in Georgia, particularly those streamgages with record through the 2013 water year. Long-term unregulated streamgages with 70 or more years of record indicate significant negative trends in the annual minimum 7-day average flow for central and southern Georgia. Watersheds for some of these streamgages have experienced minimal human impact, thus indicating that the significant negative trends observed in flows at the long-term streamgages may be influenced by changing climatological conditions. A Kendall-tau trend analysis of the annual air temperature and precipitation totals for Georgia indicated no significant trends. A comprehensive analysis of causes of the trends in annual and monthly minimum 1-day and 7-day average flows in central and southern Georgia is outside the scope of this study. Further study is needed to determine some of the causes, including both climatological and human impacts, of the significant negative trends in annual minimum 1-day and 7-day average flows in central and southern Georgia.To assess the changes in the annual 1Q10 and 7Q10 statistics over time for long-term continuous streamgages with significant trends in record, the annual 1Q10 and 7Q10 statistics were computed on a decadal accumulated basis for 39 streamgages having 40 or more years of record that indicated a significant trend. Records from most of the streamgages showed a decline in 7Q10 statistics for the decades of 1980–89, 1990–99, and 2000–09 because of the recent droughts in Georgia. Twenty four of the 39 streamgages had complete records from 1980 to 2010, and records from 23 of these gages exhibited a decline in the 7Q10 statistics during this period, ranging from –6.3 to –76.2 percent with a mean of –27.3 percent. No attempts were made during this study to adjust streamflow records or statistical analyses on the basis of trends.The monthly and annual 1Q10 and 7Q10 flow statistics for the entire period of record analyzed in the study are incorporated into the USGS StreamStatsDB, which is a database accessible to users through the recently released USGS StreamStats application for Georgia. StreamStats is a Web-based geographic information system that provides users with access to an assortment of analytical tools that are useful for water-resources planning and management, and for engineering design applications, such as the design of bridges. StreamStats allows users to easily obtain streamflow statistics, basin characteristics, and other information for user-selected streamgages.

  15. 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)

  16. 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.

  17. 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

  18. Pesticides drive risk of micropollutants in wastewater-impacted streams during low flow conditions.

    PubMed

    Munz, Nicole A; Burdon, Francis J; de Zwart, Dick; Junghans, Marion; Melo, Laura; Reyes, Marta; Schönenberger, Urs; Singer, Heinz P; Spycher, Barbara; Hollender, Juliane; Stamm, Christian

    2017-03-01

    Micropollutants enter surface waters through various pathways, of which wastewater treatment plants (WWTPs) are a major source. The large diversity of micropollutants and their many modes of toxic action pose a challenge for assessing environmental risks. In this study, we investigated the potential impact of WWTPs on receiving ecosystems by describing concentration patterns of micropollutants, predicting acute risks for aquatic organisms and validating these results with macroinvertebrate biomonitoring data. Grab samples were taken upstream, downstream and at the effluent of 24 Swiss WWTPs during low flow conditions across independent catchments with different land uses. Using liquid chromatography high resolution tandem mass spectrometry, a comprehensive target screening of almost 400 organic substances, focusing mainly on pesticides and pharmaceuticals, was conducted at two time points, and complemented with the analysis of a priority mixture of 57 substances over eight time points. Acute toxic pressure was predicted using the risk assessment approach of the multi-substance potentially affected fraction, first applying concentration addition for substances with the same toxic mode of action and subsequently response addition for the calculation of the risk of the total mixture. This toxic pressure was compared to macroinvertebrate sensitivity to pesticides (SPEAR index) upstream and downstream of the WWTPs. The concentrations were, as expected, especially for pharmaceuticals and other household chemicals higher downstream than upstream, with the detection frequency of plant protection products upstream correlating with the fraction of arable land in the catchments. While the concentration sums downstream were clearly dominated by pharmaceuticals or other household chemicals, the acute toxic pressure was mainly driven by pesticides, often caused by the episodic occurrence of these compounds even during low flow conditions. In general, five single substances

  19. Low-flow statistics of selected streams in Chester County, Pennsylvania

    USGS Publications Warehouse

    Schreffler, Curtis L.

    1998-01-01

    Low-flow statistics for many streams in Chester County, Pa., were determined on the basis of data from 14 continuous-record streamflow stations in Chester County and data from 1 station in Maryland and 1 station in Delaware. The stations in Maryland and Delaware are on streams that drain large areas within Chester County. Streamflow data through the 1994 water year were used in the analyses. The low-flow statistics summarized are the 1Q10, 7Q10, 30Q10, and harmonic mean. Low-flow statistics were estimated at 34 partial-record stream sites throughout Chester County.

  20. 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

  1. [Where is a leak point detected by "the low flow leak test" of anesthetic machines?].

    PubMed

    Omija, K; Tokumine, J; Iha, H; Uehara, M; Nitta, K; Okuda, Y

    1997-10-01

    "The low flow leak test" is recommended for pre-anesthetic inspection of anesthetic machines. We carried out anesthesia compression tests as a standard. Even in that case, often the low flow leak test does not meet the standard. We investigated the point where there is a leak in the anesthetic machine. Observing the leak that fluctuates each time there is detachment or attachment of the canister, the primary cause of the leak is thought to be related to the canister. It is important to carry out an inspection of the canister if the low flow leak test does not meet the standard.

  2. 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.

  3. Analysis of low flows and selected methods for estimating low-flow characteristics at partial-record and ungaged stream sites in western Washington

    USGS Publications Warehouse

    Curran, Christopher A.; Eng, Ken; Konrad, Christopher P.

    2012-01-01

    Regional low-flow regression models for estimating Q7,10 at ungaged stream sites are developed from the records of daily discharge at 65 continuous gaging stations (including 22 discontinued gaging stations) for the purpose of evaluating explanatory variables. By incorporating the base-flow recession time constant τ as an explanatory variable in the regression model, the root-mean square error for estimating Q7,10 at ungaged sites can be lowered to 72 percent (for known values of τ), which is 42 percent less than if only basin area and mean annual precipitation are used as explanatory variables. If partial-record sites are included in the regression data set, τ must be estimated from pairs of discharge measurements made during continuous periods of declining low flows. Eight measurement pairs are optimal for estimating τ at partial-record sites, and result in a lowering of the root-mean square error by 25 percent. A low-flow survey strategy that includes paired measurements at partial-record sites requires additional effort and planning beyond a standard strategy, but could be used to enhance regional estimates of τ and potentially reduce the error of regional regression models for estimating low-flow characteristics at ungaged sites.

  4. Low-flow characteristics of streams in the Trempealeau-Black River basin, Wisconsin

    USGS Publications Warehouse

    Holmstrom, B.K.

    1979-01-01

    Ten equations are provided to estimate low-flow characteristics at ungaged sites and at sites where one "base-flow discharge measurement is available. The low-flow characteristics determined were the annual minimum T-day mean flow below which the flow will fall on an average of once in 2 years (Qj 2) a>n<3. once in 10 years (Q7 9io)« The equations were determined from multiple-regression analyses that related the low-flow characteristics at gaging stations and low-flow partial-record stations to basin characteristics. Drainage area, soil-infiltration rate, transmissivity, precipitation, snowfall, and base-flow index were the most significant parameters for these analyses.

  5. 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.

  6. 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.

  7. [Clinical evaluation of Engström's electrically controlled ELSA for low flow closed circuit anesthesia].

    PubMed

    Igarashi, M; Nakae, Y; Ichimiya, N; Watanabe, H; Iwasaki, H; Namiki, A

    1993-02-01

    Many anesthesiologists are now interested in low flow, closed circuit anesthesia from an economical and environmental point of view. In order to evaluate clinically a newly developed electronically controlled anesthesia machine Engström's ELSA, we compared low flow, closed circuit anesthesia on 38 ASA I-II patients using ELSA, with high flow anesthesia on 12 ASA I-II patients using a conventional anesthesia machine. The results were as follows; 1. We could perform safe and economical low flow, closed circuit anesthesia using ELSA's injection vaporizer and accurate monitoring devices for O2, N2O, CO2 and concentrations of various volatile anesthetic agents. 2. Under low flow anesthesia, isoflurane consumption was 5.3 +/- 1.1 ml.h-1 x Vol.%-1 (mean +/- SE) with ELSA, which is about one fourth of the high flow anesthesia consumption (22.6 +/- 2.1 ml.h-1 x Vol.%-1 (mean +/- SE). 3. Low flow closed circuit anesthesia could maintain significantly higher temperature and humidity compared with high flow anesthesia. 4. Under low flow anesthesia of more than 7hrs, color of soda lime becomes blue, but this does not affect FIO2 nor PaCO2, and the method is clinically safe for patients.

  8. 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

  9. Low flow of streams in the Susquehanna River basin of New York

    USGS Publications Warehouse

    Randall, Allan D.

    2011-01-01

    The principal source of streamflow during periods of low flow in the Susquehanna River basin of New York is the discharge of groundwater from sand-and-gravel deposits. Spatial variation in low flow is mostly a function of differences in three watershed properties: the amount of water that is introduced to the watershed and available for runoff, the extent of surficial sand and gravel relative to till-mantled bedrock, and the extent of wetlands. These three properties were consistently significant in regression equations that were developed to estimate several indices of low flow expressed in cubic feet per second or in cubic feet per second per square mile. The equations explain 90 to 99 percent of the spatial variation in low flow. A few equations indicate that underflow that bypasses streamflow-measurement sites through permeable sand and gravel can significantly decrease low flows. Analytical and numerical groundwater-flow models indicate that spatial extent, hydraulic conductivity and thickness, storage capacity, and topography of stratified sandand- gravel deposits affect low-flow yields from those deposits. Model-simulated discharge of groundwater to streams at low flow reaches a maximum where hydraulic-conductivity values are about 15 feet per day (in valleys 0.5 mile wide) to 60 feet per day (in valleys 1 mile wide). These hydraulic-conductivity values are much larger than those that are considered typical of till and bedrock, but smaller than values reported for productive sand-and-gravel aquifers in some valley reaches in New York. Differences in the properties of till and bedrock and in land-surface slope or relief within the Susquehanna River basin of New York apparently have little effect on low flow. Three regression equations were selected for practical application in estimating 7-day mean low flows in cubic feet per second with 10-year and 2-year recurrence intervals, and 90-percent flow duration, at ungaged sites draining more than 30 square miles

  10. Evidence of population resistance to extreme low flows in a fluvial-dependent fish species

    USGS Publications Warehouse

    Katz, Rachel A.; Freeman, Mary C.

    2015-01-01

    Extreme low streamflows are natural disturbances to aquatic populations. Species in naturally intermittent streams display adaptations that enhance persistence during extreme events; however, the fate of populations in perennial streams during unprecedented low-flow periods is not well-understood. Biota requiring swift-flowing habitats may be especially vulnerable to flow reductions. We estimated the abundance and local survival of a native fluvial-dependent fish species (Etheostoma inscriptum) across 5 years encompassing historic low flows in a sixth-order southeastern USA perennial river. Based on capturemark-recapture data, the study shoal may have acted as a refuge during severe drought, with increased young-of-the-year (YOY) recruitment and occasionally high adult immigration. Contrary to expectations, summer and autumn survival rates (30 days) were not strongly depressed during low-flow periods, despite 25%-80% reductions in monthly discharge. Instead, YOY survival increased with lower minimum discharge and in response to small rain events that increased low-flow variability. Age-1+ fish showed the opposite pattern, with survival decreasing in response to increasing low-flow variability. Results from this population dynamics study of a small fish in a perennial river suggest that fluvial-dependent species can be resistant to extreme flow reductions through enhanced YOY recruitment and high survival

  11. 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

  12. 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.

  13. A comparison of low flow pumping and bailing for VOC groundwater sampling at landfills

    SciTech Connect

    Svavarsson, G.; Connelly, J.; Kuehling, H.

    1995-12-31

    The state of Wisconsin has more than 10,000 groundwater monitoring wells that will continue to be sampled into the future. Most samplers in this state use a bailer to purge and sample these wells. The EPA has questioned the use of a bailer for volatile organic compound (VOC) sampling because of the potential to increase sample aeration and cause significantly more turbidity than using a low flow pumping method. A total of nine monitoring wells that had a history of VOC contamination were sampled at three landfills. The wells were sampled using both a low flow pump and bailer in the summer of 1994 and again in the following winter. Generally, only small differences were found between the VOC results collected using the low flow pumping and the bailing techniques. In addition, the method resulting in higher recovery of organic compounds differed, depending on the particular well, season, and compound.

  14. Smart low flow signature metrics for an improved overall performance evaluation of hydrological models

    NASA Astrophysics Data System (ADS)

    Pfannerstill, Matthias; Guse, Björn; Fohrer, Nicola

    2014-03-01

    Hydrological models have to be calibrated accurately to provide reasonable model results. For a concise model evaluation, the different phases of the hydrograph have to be considered in multi-metric frameworks with appropriate performance metrics. Low and high flows need to be reproduced simultaneously without neglecting the other phases of the hydrograph. In this paper, we highlight the relevance of very low and low flows with separate performance metrics. We present a multi-metric evaluation framework to identify calibration runs, which represent the different phases of the hydrograph precisely. A stepwise evaluation was done with commonly used statistical performance metrics (Nash-Sutcliffe, percent bias) and signature metrics, which are based on the flow duration curve (FDC). In order to consider a fairly balanced evaluation between high and low flow phases, we divided the flow duration curve into segments of high, medium and low flow phases, and additionally into very high and very low flow phases. The model performance in these segments was evaluated separately with the root mean square error (RMSE). Our results show that this evaluation method leads to an improved selection of good calibration runs to enhance the overall model performance by the refined segmentation of FDC. By combining performance metrics for high flow conditions with low flow conditions, this study demonstrates the challenge of calibrating a model with a satisfactory performance in high and low phases simultaneously. Consequently, we conclude that an additional performance metric for very low flows should be included in model analyzes to improve the overall performance in all phases of the hydrograph.

  15. 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.

  16. 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...

  17. 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...

  18. Economic method for measuring ultra-low flow rates of fluids

    NASA Technical Reports Server (NTRS)

    Bogdanovic, J. A.; Keller, W. F.

    1970-01-01

    Capillary tube flowmeter measures ultra-low flows of very corrosive fluids /such as chlorine trifluoride and liquid fluorine/ and other liquids with reasonable accuracy. Flowmeter utilizes differential pressure transducer and operates on the principle that for laminar flow in the tube, pressure drop is proportional to flow rate.

  19. [The current state of leak in anesthetic machines detected by low flow leak tests].

    PubMed

    Uehara, M; Tokumine, J; Iha, H; Nitta, K; Okuda, Y

    1999-05-01

    To assess the current state of leak in anesthetic machines, we selected 66 units of anesthetic machines for inspection and repair from various medical institutions. Based on a newly designed inspection flow chart a low flow leak test for internal circuits of the anesthetic machines was performed. The conventional low flow leak test was also performed for smooth detection of leak for rational evaluation. Only 39% of the anesthetic machines met the standard of the low flow leak tests, and leak was detected in the remaining 61%. The average residual leak mounted to 0.97 l.min-1, with the maximum of 5.3 l.min-1. Canisters, corrugated tubes, and vaporizers were considered the primary causes of leak. After the inspection and repair, leak in 77.5% of the anesthetic machines either disappeared or decreased and the average residual leak dropped to 0.34 l.min-1. However, 47% of the anesthetic machines still failed to meet the standard of the low flow leak tests. To further improve the situation, more detailed inspection and repair are necessary especially for precise detection of the cause of leak in the internal circuit of anesthetic machines which often remains undetected.

  20. Novel radiator for carbon dioxide absorbents in low-flow anesthesia.

    PubMed

    Hirabayashi, Go; Mitsui, Takanori; Kakinuma, Takayasu; Ogihara, Yukihiko; Matsumoto, Shohei; Isshiki, Atsushi; Yasuo, Watanabe

    2003-01-01

    During long-term low-flow sevoflurane anesthesia, dew formation and the generation of compound A are increased in the anesthesia circuit because of elevated soda lime temperature. The object of this study was to develop a novel radiator for carbon dioxide absorbents used for long durations of low-flow sevoflurane anesthesia. Eleven female swine were divided into two groups comprising a "radiator" group (n = 5) that used a novel radiator for carbon dioxide absorbents and a "control" group (n = 6) that used a conventional canister. Anesthesia was maintained with N2O, O2, and sevoflurane, and low-flow anesthesia was performed with fresh gas flow at 0.6 L/min for 12 hr. In the "control" group, the soda lime temperature reached more than 40 degrees C and soda lime dried up with severe dew formation in the inspiratory valve. In the "radiator" group, the temperature of soda lime stayed at 30 degrees C, and the water content of soda lime was retained with no dew formation in the inspiratory valve. In addition, compound A concentration was reduced. In conclusion, radiation of soda lime reduced the amounts of condensation formed and the concentration of compound A in the anesthetic circuit, and allowed long term low-flow anesthesia without equipment malfunction.

  1. 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

  2. Low-flow characteristics at gaging stations on the Wisconsin, Fox, and Wolf rivers, Wisconsin

    USGS Publications Warehouse

    Gebert, W.A.; Holmstrom, B.K.

    1977-01-01

    The magnitude of the low-flow characteristics are in some instances affected by the period of record. These characteristics can vary as much as ±30 percent at some gaging stations depending on whether or not the severe drought of the 1930's was included in the analysis.

  3. 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.

  4. 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

  5. Role of Transesophageal Echocardiography in the Diagnosis of Paradoxical Low Flow, Low Gradient Severe Aortic Stenosis

    PubMed Central

    Abudiab, Muaz M.; Pandit, Anil

    2017-01-01

    Background and Objectives Prior studies indicate that up to 35% of cases of severe aortic stenosis (AS) have paradoxical low flow, low gradient despite preserved left ventricular ejection fraction (LVEF). However, error in left ventricular outflow tract (LVOT) diameter may lead to misclassification. Herein, we determined whether measurement of LVOT diameter by transesophageal echocardiography (TEE) results in reclassification of cases to non-severe AS. Subjects and Methods Patients with severe AS with aortic valve area (AVA) <1 cm2 by transthoracic echocardiography (TTE) within 6 months were studied. Paradoxical low flow, low gradient was defined as mean Doppler gradient (MG) <40 mm Hg and stroke volume index (SVI) ≤35 mL/m2. Preserved LVEF was defined as ≥0.50. Results Among 108 patients, 12 (15%) had paradoxical low flow, low gradient severe AS despite preserved LVEF based on TTE measurement. When LVOT diameter by TEE in 2D was used, only 5 (6.3%) patients had low flow, low gradient severe AS (p<0.001). Coefficients of variability for intraobserver and interobserver measurement of LVOT were <10%. However, the limits of agreement between TTE and TEE measurement of LVOT ranged from 0.43 cm (95% confidence interval [CI]: 0.36 to 0.5) to -0.31 cm (95% CI: -0.38 to -0.23). Conclusion TEE measured LVOT diameter may result in reclassification to moderate AS in some patients due to low prevalence of true paradoxical low flow, low gradient (PLFLG) severe AS. PMID:28154595

  6. 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.

  7. A three-pillar approach to assessing climate impacts on low flows

    NASA Astrophysics Data System (ADS)

    Laaha, Gregor; Parajka, Juraj; Viglione, Alberto; Koffler, Daniel; Haslinger, Klaus; Schöner, Wolfgang; Zehetgruber, Judith; Blöschl, Günter

    2016-09-01

    The objective of this paper is to present a framework for assessing climate impacts on future low flows that combines different sources of information, termed pillars. To illustrate the framework three pillars are chosen: (a) extrapolation of observed low-flow trends into the future, (b) rainfall-runoff projections based on climate scenarios and (c) extrapolation of changing stochastic rainfall characteristics into the future combined with rainfall-runoff modelling. Alternative pillars could be included in the overall framework. The three pillars are combined by expert judgement based on a synoptic view of data, model outputs and process reasoning. The consistency/inconsistency between the pillars is considered an indicator of the certainty/uncertainty of the projections. The viability of the framework is illustrated for four example catchments from Austria that represent typical climate conditions in central Europe. In the Alpine region where winter low flows dominate, trend projections and climate scenarios yield consistently increasing low flows, although of different magnitudes. In the region north of the Alps, consistently small changes are projected by all methods. In the regions in the south and south-east, more pronounced and mostly decreasing trends are projected but there is disagreement in the magnitudes of the projected changes. The process reasons for the consistencies/inconsistencies are discussed. For an Alpine region such as Austria the key to understanding low flows is whether they are controlled by freezing and snowmelt processes, or by the summer moisture deficit associated with evaporation. It is argued that the three-pillar approach offers a systematic framework of combining different sources of information aimed at more robust projections than that obtained from each pillar alone.

  8. Unsteady flow at low flow-rate region in a semi-open propeller fan (velocity fluctuation outside of blade tip)

    NASA Astrophysics Data System (ADS)

    Shiomi, Norimasa; Kinoue, Yoichi; Jin, Ying-Zi; Liu, Pin; Setoguchi, Toshiaki

    2011-09-01

    In order to clarify the unsteady flow fields at low flow-rate region with positive gradient on pressure — flow-rate curve, the experimental investigation was carried out at rotor inlet and outside of rotor blade tip without casing in a semi-opened propeller fan using a hot-wire anemometer. A single I-type hot-wire probe was used, and the data obtained were processed by the use of phase-locked averaging, ensemble averaging and FFT analyzing. The flow fields at rotor inlet and outside of rotor blade tip were discussed mainly using the results from distributions of velocity fluctuations and power spectrum density. It was found from these results that there are the two types of different periodical fluctuations and both of those frequencies were not the same of rotor rotating frequency (RRF; 15Hz). One was observed at relatively high flow-rate region at relatively downstream area in measurement and its frequency was approximately 7Hz (47% of RRF). The other was observed at relatively low flow-rate region at relatively upstream area in measurement and its frequency was approximately 10Hz (67% of RRF)". As the velocity fluctuations with the flow fields are rapidly increased by the former fluctuation, it is thought that its fluctuation is the trigger of blade stall.

  9. 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

  10. 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

  11. 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.

  12. Low flow water quality in rivers; septic tank systems and high-resolution phosphorus signals.

    PubMed

    Macintosh, K A; Jordan, P; Cassidy, R; Arnscheidt, J; Ward, C

    2011-12-15

    Rural point sources of phosphorus (P), including septic tank systems, provide a small part of the overall phosphorus budget to surface waters in agricultural catchments but can have a disproportionate impact on the low flow P concentration of receiving rivers. This has particular importance as the discharges are approximately constant into receiving waters and these have restricted dilution capacity during ecologically sensitive summer periods. In this study, a number of identified high impact septic systems were replaced with modern sequential batch reactors in three rural catchments during a monitoring period of 4 years. Sub-hourly P monitoring was conducted using bankside-analysers. Results show that strategic replacement of defective septic tank systems with modern systems and polishing filters decreased the low flow P concentration of one catchment stream by 0.032 mg TPL(-1) (0.018 mg TRPL(-1)) over the 4 years. However two of the catchment mitigation efforts were offset by continued new-builds that increased the density of septic systems from 3.4 km(-2) to 4.6 km(-2) and 13.8 km(-2) to 17.2 km(-2) and subsequently increased low flow P concentrations. Future considerations for septic system mitigation should include catchment carrying capacity as well as technology changes.

  13. Low-flow, base-flow, and mean-flow regression equations for Pennsylvania streams

    USGS Publications Warehouse

    Stuckey, Marla H.

    2006-01-01

    Low-flow, base-flow, and mean-flow characteristics are an important part of assessing water resources in a watershed. These streamflow characteristics can be used by watershed planners and regulators to determine water availability, water-use allocations, assimilative capacities of streams, and aquatic-habitat needs. Streamflow characteristics are commonly predicted by use of regression equations when a nearby streamflow-gaging station is not available. Regression equations for predicting low-flow, base-flow, and mean-flow characteristics for Pennsylvania streams were developed from data collected at 293 continuous- and partial-record streamflow-gaging stations with flow unaffected by upstream regulation, diversion, or mining. Continuous-record stations used in the regression analysis had 9 years or more of data, and partial-record stations used had seven or more measurements collected during base-flow conditions. The state was divided into five low-flow regions and regional regression equations were developed for the 7-day, 10-year; 7-day, 2-year; 30-day, 10-year; 30-day, 2-year; and 90-day, 10-year low flows using generalized least-squares regression. Statewide regression equations were developed for the 10-year, 25-year, and 50-year base flows using generalized least-squares regression. Statewide regression equations were developed for harmonic mean and mean annual flow using weighted least-squares regression. Basin characteristics found to be significant explanatory variables at the 95-percent confidence level for one or more regression equations were drainage area, basin slope, thickness of soil, stream density, mean annual precipitation, mean elevation, and the percentage of glaciation, carbonate bedrock, forested area, and urban area within a basin. Standard errors of prediction ranged from 33 to 66 percent for the n-day, T-year low flows; 21 to 23 percent for the base flows; and 12 to 38 percent for the mean annual flow and harmonic mean, respectively. The

  14. 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

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

    NASA Astrophysics Data System (ADS)

    Vidal, Jean-Philippe; Hingray, Benoît; Magand, Claire; Sauquet, Eric; Ducharne, Agnès

    2016-09-01

    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. This framework thus allows deriving a hierarchy of climate and hydrological uncertainties, which depends on the time horizon considered. It 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 data set of transient hydrological projections that combines in a comprehensive way 11 runs from four different GCMs, three SDMs with 10 stochastic realizations each, as well as six diverse HMs. The change signal is a decrease in yearly low flows of around -20  % in 2065, except for the more 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 is however detected for low-flow averages over 30-year time slices starting as early as 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

  16. 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

  17. Low-flow appliances and household water demand: an evaluation of demand-side management policy in Albuquerque, New Mexico.

    PubMed

    Price, James I; Chermak, Janie M; Felardo, Jeff

    2014-01-15

    Residential rebate programs for low-flow water devices have become increasingly popular as a means of reducing urban water demand. Although program specifics vary, low-flow rebates are available in most U.S. metropolitan areas, as well as in many smaller municipalities. Despite their popularity, few statistical analyses have been conducted regarding the effects of low-flow rebates on household water use. In this paper, we consider the effects of rebates from the Albuquerque Bernalillo County Water Utility Authority (ABCWUA). Using panel regression techniques with a database of rebate recipients, we estimate the marginal effects of various low-flow devices on household water demand. Results indicate a negative correlation between household water use and the presence of most low-flow devices, after controlling for water price and weather conditions. Low-flow toilets have the greatest impact on water use, while low-flow washing machines, dishwashers, showerheads, and xeriscape have smaller but significant effects. In contrast, air conditioning systems, hot water recirculators, and rain barrels have no significant impact on water use. We also test for possible rebound effects (i.e. whether low-flow appliances become less-effective over time due to poor rates of retention or behavioral changes) and compare the cost effectiveness of each rebate using levelised-costs. We find no evidence of rebound effects and substantial variation in levelised-costs, with low-flow showerheads being the most cost-effective device under the current ABCWUA rebate program. The latter result suggests that water providers can improve the efficiency of rebate programs by targeting the most cost-effective devices.

  18. Hepatic microvascular regulatory mechanisms. VIII. Glucogenic responses and morphologic changes following serotonin-induced low flow.

    PubMed

    Reilly, F D; McCafferty, R E; McCuskey, P A; Dimlich, R V

    1986-01-01

    Changes in blood glucose, hepatic glycogen content and distribution, the number of hepatic mast cells, and hepatic morphology were assessed over 30 min in non-fasted and anesthetized Sprague-Dawley rats receiving endoportal or femoral intravenous injections of selected doses of serotonin and/or phentolamine, lodoxamide, or of Ringer's solution (control). Endoportal administration of low-flow producing doses of serotonin (1.0, 10.0, 20.0 micrograms per 100 g b.w.) elevated circulating blood glucose without decreasing hepatic glycogen content when compared to control in unit dry or wet weights. Hyperglycemia was accompanied by centrilobular glycogen depletion and apparent Kupffer cell activation. However, no change in hepatocyte or endothelial cell morphology or in the number of hepatic mast cells was observed following serotonin-induced low flow. The glucotropic response to a nonhypotensive dose of serotonin (1.0 microgram per 100 g b.w.) was modified by phentolamine (100 micrograms per 100 g b.w.) but not lodoxamide (0.1 microgram per 100 g b.w.). These blockers, when given alone, stimulated centrilobular glycogen depletion without producing a net change in blood glucose or hepatic glycogen content. By contrast, injection of serotonin (10.0 micrograms per 100 g b.w.) and/or phentolamine (100 micrograms per 100 g b.w.) into the femoral vein provoked no glucogenesis or systemic hypotension. Given these results, serotonin is suggested to stimulate hyperglycemia by activating alpha-adrenergic receptors. Since centrilobular glycogen depletion proceeds with no detectable change in total hepatic glycogen content, it is postulated that hepatic glycogen catabolism and deposition occur simultaneously and at equivalent rates during conditions of serotonin-induced hyperglycemia and low flow.

  19. 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.

  20. Tree leaf control on low flow water quality in a small Virginia stream

    USGS Publications Warehouse

    Slack, K.V.; Feltz, H.R.

    1968-01-01

    Impaired water quality in a small stream was related to autumn leaf fall from riparian vegetation. Dissolved oxygen and pH decreased, and water color, specific conductance, iron, manganese, and bicarbonate values increased as the rate of leaf fall increased. Similar quality changes occurred in laboratory cultures of tree leaves in filtered stream water, but the five leaf species studied produced widely differing results. Stream quality improved rapidly following channel flushing by storm flow. Organic loading by tree litter can exert significant control on water composition, especially during low flow.

  1. 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

  2. Use of Low-Flow Trend and Transfer-Function Models to Determine Relation of Low Flows to Regional Urbanization and Precipitation, Rahway River Basin, New Jersey, 1940-91

    USGS Publications Warehouse

    Barringer, Thomas H.; Reiser, Robert G.; Price, Curtis V.

    2000-01-01

    The Rahway River Basin in northern New Jersey has become heavily urbanized. The importance of the Rahway River as a water-supply source for the region led to an investigation of trends in the river's low-flow characteristics over time and their relation to regional urbanization and precipitation. Since 1950, low flows at a stream-gaging station near Springfield, N.J., increasingly have tended to exceed those at a station at Rahway. Polynomial-trend models for three measures of low-flow difference between the two stations during 1940-91 show trends in all three measures, indicating that they have changed significantly in level during the study period. Transfer-function models indicate that differences in low flows between the two gaging stations are significantly related to measures of basin urbanization and regional precipitation. A rough water budget for the inter-gage part of the basin confirms these results.

  3. Paradoxical low flow aortic valve stenosis: incidence, evaluation, and clinical significance.

    PubMed

    Clavel, Marie-Annick; Pibarot, Philippe; Dumesnil, Jean G

    2014-01-01

    Paradoxical low-flow (PLF) aortic stenosis is defined by a stroke volume index <35 ml/m(2) despite the presence of preserved LV ejection fraction (≥ 50 %). This entity is typically characterized by pronounced LV concentric remodeling with small LV cavity, impaired LV filling, increased arterial load, and reduced LV longitudinal shortening. Patients with PLF also have a worse prognosis compared to patients with normal flow. Because of the low flow state, these patients often have a low gradient despite the presence of severe stenosis, thus leading to discordant AS grading (i.e., aortic valve area < 1.0 cm(2) but mean gradient < 40 mmHg) and thus uncertainty about the indication of aortic valve replacement. Stress echocardiography and aortic valve calcium score by computed tomography may be helpful to differentiate true from pseudo severe stenosis and thereby guide therapeutic management in these patients. Aortic valve replacement improves outcomes in patients with PLF low gradient AS having evidence of severe stenosis. Transcatheter aortic valve replacement may provide an interesting alternative to surgery in these patients.

  4. Low-flow hydraulic conductivity tests at wells that cross the water table.

    PubMed

    Aragon-Jose, Alejandra T; Robbins, Gary A

    2011-01-01

    Wells with screens and sand packs that cross the water table represent a challenging problem for determining hydraulic conductivity by slug testing due to sand pack drainage and resaturation. Sand pack drainage results in a multisegmented recovery curve. One must then subjectively pick a portion of the curve to analyze. Sand pack drainage also results in a change in the effective radius of the well which requires a guess at the porosity or specific yield in analyzing the test. In the study of Robbins et al. (2009), a method was introduced to obtain hydraulic conductivity in monitoring wells using the steady-state drawdown and flow rate obtained during low-flow sampling. The method was tested in this study in wells whose screens cross the water table and shown to avoid sand pack drainage problems that complicate analyzing slug tests. In applying the method to low-flow sampling, only a single pair of steady-state flow rate and drawdown are needed; hence, to derive meaningful results, an accurate determination of these parameters is required.

  5. Irregular changes in the structure of flowing blood at low flow conditions.

    PubMed

    Pribush, Alexander; Meiselman, Herbert J; Meyerstein, Dan; Meyerstein, Naomi

    2009-12-01

    The structural organization of the dispersed phase of blood was studied by measuring the conductance (G) and the capacitance (C) of red blood cell (RBC) suspensions flowing in a vertical channel. Steady-state C and G signals exhibit erratic fluctuations around mean values; the root mean square of the fluctuating signals decreases rapidly as the average flow rate () increases from 0.21 to ~4.17 mm/s and then less rapidly at higher velocities. The intensity of oscillations is substantially reduced for suspensions with weaker aggregating media. Analysis of the fluctuations performed in the framework of the equivalent electrical circuits for flowing blood gives rise to the following conclusions: (1) Instantaneous hematocrit (Hct) and velocity cross-stream profiles are non-smooth functions of radial position. (2) Oscillations of conductance at low flow conditions reflect irregular changes in the RBC network structure caused by fluctuations of aggregation-disaggregation equilibrium in the non-uniform shear field. (3) A transformation of the rheological behavior of RBC suspensions from shear-thinning to shear-thickening in a low flow regime amplifies fluctuations of aggregation-disaggregation equilibrium.

  6. Low-flow profiles of the upper Oconee 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 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 Oconee River and tributaries in Georgia 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 second in a series of reports that will cover all stream basins north of the Fall Line in Georgia. It includes the Oconee River basin down to and including Camp Creek at stream mile 134.53, Town Creek in Baldwin and Hancock Counties down to County Road 213-141, and Buffalo Creek in Hancock County down to the Hancock-Washington 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)

  7. Role of impaired CO2 reactivity in the diagnosis of cerebral low flow infarcts.

    PubMed Central

    Baumgartner, R W; Regard, M

    1994-01-01

    Previous studies on CO2 reactivity in cerebral low flow infarcts (LFIs) included patients with lesions in the frontoparasagittal area, supraganglionic white matter, and temporoparieto-occipital zone. Supraganglionic white matter LFIs are, however, difficult to separate from non-low flow induced infarcts of the lacunar type, and temporoparieto-occipital LFIs from infarcts in the territory of the inferior stem of the middle cerebral artery. The CO2 reactivity of the middle cerebral artery was studied in 56 patients with high grade stenoses and occlusions of the internal carotid artery and LFIs (n = 9) in the frontoparasagittal border zone, territorial infarcts (n = 26), no infarcts (n = 21), and normal subjects (n = 25) by means of transcranial Doppler sonography. The aim was to investigate whether patients with LFIs have significantly lower CO2 reactivity than patients with territorial infarcts, no infarcts, and normal subjects. Patients with LFIs had the most severely reduced CO2 reactivity on the symptomatic side and CO2 reactivity was significantly lower than on the asymptomatic side. It was also lower than in patients with unilateral and bilateral internal carotid artery obstructions and territorial infarcts, asymptomatic patients, and healthy volunteers. It is concluded that LFIs are associated with significantly reduced CO2 reactivity. PMID:8021667

  8. 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.

  9. 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)

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

    USGS Publications Warehouse

    Flippo, H.N.

    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. 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

    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.

  12. Modeling Low-Flow Sensitivity to Climate Variability and Forest Harvesting in the Willamette Basin: A Multi-scale Approach.

    NASA Astrophysics Data System (ADS)

    Choate, J.; Tague, C.; Grant, G.

    2002-12-01

    In the mountainous region of the Pacific Northwest, underlying geologic and vegetation patterns, forest management practices and climate regimes at different elevations mediate the response of low flows occurring in late summer. Low-stream flow conditions, occurring during the warm, dry summers are critical to river ecosystem function and crucial to many aquatic and riparian species life cycles as well as human uses of streams. Understanding the different controls on low flow variability in this region requires a multi-scale perspective. This particular study is part of a larger strategy designed to use both empirical analysis and physically based, hydro-ecological modeling to disentangle the role that climate, geology and forest harvesting play in controlling low flows in 1st to 5th order watersheds within the Willamette basin. Our empirical analysis of summer low flow for a range of streams has shown that summer, unit-area discharge volumes are significantly lower for streams in the geologically distinct and low elevation Western Cascade versus High Cascade areas. This empirical analysis outlines large-scale regional variability. To assess and compare this with smaller scale variability, we use the RHESSys model (Regional Hydro-Ecologic Simulation System) to assess low flow behavior for small 1st order streams within the Western Cascade region. The goal is to examine low flow variability due to both climate and forest harvesting and recovery and place this in the context of regional scale analysis. We use multiple simulations to predict low flow volumes under cut and uncut conditions for wet/dry and warm/cool climate scenarios. Future work will replicate this study to examine 1st order watershed sensitivity within the contrasting High Cascade geologic region. The combined multi-scale empirical and modeling approach will then be used to provide a more comprehensive assessment of low flow patterns and sensitivity within this region.

  13. 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...

  14. Quantifying the impact of low flow periods on bed topography and bedload transport rates

    NASA Astrophysics Data System (ADS)

    Masteller, C.; Finnegan, N. J.

    2015-12-01

    Despite the large body of scientific work focused on bedload transport, it remains difficult to predict accurately. Most empirical formulations cast the bedload flux rate as a function of shear stress acting on the bed in excess of a defined threshold value. This critical stress divides the hydrograph into two portions, an above threshold regime associated with bedload transport and a below threshold regime, where transport does not occur. The bulk of previous studies have concentrated on the portion of the hydrograph above threshold, leaving the below threshold region largely unexplored. A small number of previous studies suggest that increased time between transport events results in decreases in bedload flux rates. In many cases, these decreases in transport are attributed to compaction of the bed. Compaction potentially decreases mobility by increasing the friction on individual grains and the friction angle of particles that have settled into pockets. However, changes in bed topography during low flow have not been explicitly linked to changes in subsequent behavior during transport events. In this study, we carry out flume experiments to examine the impact of sub-critical threshold flow duration on surface grain size, bed topography, and bedload flux rates. Preliminary experimental findings using a 5 m tilting flume with an 8 mm D50 grain size mixture indicate that transport rate is very sensitive to low flow duration, consistent with previous studies. We generate high-resolution topographic maps of the bed surface using Structure from Motion photogrammetry. Analysis of bed topography indicates that reduced transport rates are associated with lower mean bed elevation and standard deviation of bed topography. Specifically, we document reductions in transport rates of ~30% associated with reductions in bed topography on the order of 50% of D50 and changes in the standard deviation of bed topography on the order of 100% of D50. Automated analysis of median

  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. 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.

  17. Development of a liquid-junction/low-flow interface for phosphate buffer capillary electrophoresis mass spectrometry.

    PubMed

    Li, Fu-An; Huang, Ju-Li; Shen, Shang-Yu; Wang, Che-Wei; Her, Guor-Rong

    2009-04-01

    To alleviate ion suppression from phosphate buffer and to preserve separation integrity, a new capillary electrophoresis mass spectrometry (CE-MS) interface was developed. The interface consisted of a low-flow interface and a liquid junction. In this design, both the inlet reservoir and the liquid-junction reservoir were filled with phosphate running buffer. Because the phosphate anions in the column migrated toward the inlet reservoir (away from the electrospray ionization (ESI) source) the problem of ion suppression in ESI was avoided. The liquid junction was incorporated to eliminate issues of degraded separation observed when sheath liquid interfaces use different buffers for separation and MS analysis attributed to differences in anion velocity. The utility of the interface was demonstrated by the analysis of antihistamines at pH 3.5 and the analysis of perfluorocarboxylic acid at pH 9.5.

  18. Automated low-flow ascites pump for the treatment of cirrhotic patients with refractory ascites.

    PubMed

    Stirnimann, Guido; Banz, Vanessa; Storni, Federico; De Gottardi, Andrea

    2017-02-01

    Cirrhotic patients with refractory ascites (RA) can be treated with repeated large volume paracentesis (LVP), with the insertion of a transjugular intrahepatic portosystemic shunt (TIPS) or with liver transplantation. However, side effects and complications of these therapeutic options, as well as organ shortage, warrant the development of novel treatments. The automated low-flow ascites pump (alfapump(®)) is a subcutaneously-implanted novel battery-driven device that pumps ascitic fluid from the peritoneal cavity into the urinary bladder. Ascites can therefore be aspirated in a time- and volume-controlled mode and evacuated by urination. Here we review the currently available data about patient selection, efficacy and safety of the alfapump and provide recommendations for the management of patients treated with this new method.

  19. Automated low-flow ascites pump for the treatment of cirrhotic patients with refractory ascites

    PubMed Central

    Stirnimann, Guido; Banz, Vanessa; Storni, Federico; De Gottardi, Andrea

    2017-01-01

    Cirrhotic patients with refractory ascites (RA) can be treated with repeated large volume paracentesis (LVP), with the insertion of a transjugular intrahepatic portosystemic shunt (TIPS) or with liver transplantation. However, side effects and complications of these therapeutic options, as well as organ shortage, warrant the development of novel treatments. The automated low-flow ascites pump (alfapump®) is a subcutaneously-implanted novel battery-driven device that pumps ascitic fluid from the peritoneal cavity into the urinary bladder. Ascites can therefore be aspirated in a time- and volume-controlled mode and evacuated by urination. Here we review the currently available data about patient selection, efficacy and safety of the alfapump and provide recommendations for the management of patients treated with this new method. PMID:28203285

  20. Impaired contractile recovery after low-flow myocardial ischemia in a porcine model of metabolic syndrome.

    PubMed

    Huang, Janice V; Lu, Li; Ye, Shuyu; Bergman, Bryan C; Sparagna, Genevieve C; Sarraf, Mohammad; Reusch, Jane E B; Greyson, Clifford R; Schwartz, Gregory G

    2013-03-15

    Clinical metabolic syndrome conveys a poor prognosis in patients with acute coronary syndrome, not fully accounted for by the extent of coronary atherosclerosis. To explain this observation, we determined whether postischemic myocardial contractile and metabolic function are impaired in a porcine dietary model of metabolic syndrome without atherosclerosis. Micropigs (n = 28) were assigned to a control diet (low fat, no added sugars) or an intervention diet (high saturated fat and simple sugars, no added cholesterol) for 7 mo. The intervention diet produced obesity, hypertension, dyslipidemia, and impaired glucose tolerance, but not atherosclerosis. Under open-chest, anesthetized conditions, pigs underwent 45 min of low-flow myocardial ischemia and 120 min of reperfusion. In both diet groups, contractile function was similar at baseline and declined similarly during ischemia. However, after 120 min of reperfusion, regional work recovered to 21 ± 12% of baseline in metabolic syndrome pigs compared with 61 ± 13% in control pigs (P = 0.01). Ischemia-reperfusion caused a progressive decline in mechanical/metabolic efficiency (regional work/O2 consumption) in metabolic syndrome hearts, but not in control hearts. Metabolic syndrome hearts demonstrated altered fatty acyl composition of cardiolipin and increased Akt phosphorylation in both ischemic and nonischemic regions, suggesting tonic activation. Metabolic syndrome hearts used more fatty acid than control hearts (P = 0.03). When fatty acid availability was restricted by prior insulin exposure, differences between groups in postischemic contractile recovery and mechanical/metabolic efficiency were eliminated. In conclusion, pigs with characteristics of metabolic syndrome demonstrate impaired contractile and metabolic recovery after low-flow myocardial ischemia. Contributory mechanisms may include remodeling of cardiolipin, abnormal activation of Akt, and excessive utilization of fatty acid substrates.

  1. Impaired contractile recovery after low-flow myocardial ischemia in a porcine model of metabolic syndrome

    PubMed Central

    Huang, Janice V.; Lu, Li; Ye, Shuyu; Bergman, Bryan C.; Sparagna, Genevieve C.; Sarraf, Mohammad; Reusch, Jane E. B.; Greyson, Clifford R.

    2013-01-01

    Clinical metabolic syndrome conveys a poor prognosis in patients with acute coronary syndrome, not fully accounted for by the extent of coronary atherosclerosis. To explain this observation, we determined whether postischemic myocardial contractile and metabolic function are impaired in a porcine dietary model of metabolic syndrome without atherosclerosis. Micropigs (n = 28) were assigned to a control diet (low fat, no added sugars) or an intervention diet (high saturated fat and simple sugars, no added cholesterol) for 7 mo. The intervention diet produced obesity, hypertension, dyslipidemia, and impaired glucose tolerance, but not atherosclerosis. Under open-chest, anesthetized conditions, pigs underwent 45 min of low-flow myocardial ischemia and 120 min of reperfusion. In both diet groups, contractile function was similar at baseline and declined similarly during ischemia. However, after 120 min of reperfusion, regional work recovered to 21 ± 12% of baseline in metabolic syndrome pigs compared with 61 ± 13% in control pigs (P = 0.01). Ischemia-reperfusion caused a progressive decline in mechanical/metabolic efficiency (regional work/O2 consumption) in metabolic syndrome hearts, but not in control hearts. Metabolic syndrome hearts demonstrated altered fatty acyl composition of cardiolipin and increased Akt phosphorylation in both ischemic and nonischemic regions, suggesting tonic activation. Metabolic syndrome hearts used more fatty acid than control hearts (P = 0.03). When fatty acid availability was restricted by prior insulin exposure, differences between groups in postischemic contractile recovery and mechanical/metabolic efficiency were eliminated. In conclusion, pigs with characteristics of metabolic syndrome demonstrate impaired contractile and metabolic recovery after low-flow myocardial ischemia. Contributory mechanisms may include remodeling of cardiolipin, abnormal activation of Akt, and excessive utilization of fatty acid substrates. PMID:23335793

  2. 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).

  3. 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.

  4. 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)

  5. 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

  6. 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

  7. 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

  8. 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

  9. Estimation of low flow sensitivity to climate and land-use changes using a parsimonious water balance model

    NASA Astrophysics Data System (ADS)

    Brena, A.; Schneider, J.; Stahl, K.; Weiler, M.

    2009-04-01

    There is considerable interest in systematically estimating the impact of climate and environmental changes to particular characteristics of hydrological regimes across large regions. This study presents the development and first application of a regionalised parsimonious model to estimate the sensitivity of the summer low flow period in British Columbia, Canada. Here, summer low flows are maintained through the release of water from groundwater storage, flow from channel banks, lakes and wetlands. Low flows are important for water-supply planning and design, and maintenance of quantity and quality of water for irrigation, recreation, and fish and wildlife conservation. There have been concerns recently that climate warming and land cover changes due to an unprecedented pine beetle epidemic may cause a deterioration of water quality during low flow periods and at certain times may become a hazard to ecosystem and to water management schemes. A parsimonious water balance model based on a simple transfer function approach was developed to characterize the recession curve of the hydrological regime. The purpose of the model is to transform a distributed effective water input into a characteristic hydrologic regime at the outlet of the catchment. The distributed effective water input is derived from gridded 30-year mean monthly precipitation and temperature data (disaggregated to a daily resolution) that is first modified by evapotranspiration and by a degree-day based snow accumulation and snowmelt model. The two model parameters of the non-linear transfer function were fitted to the characteristic hydrographs of a sample of gauged catchments with different size, elevation, climate, and hydrological regime. Based on their relation to catchment characteristics, the model parameters were then regionalized for a large area of British Columbia. A first application estimates the sensitivity of the low flow season to simple delta-change climate scenarios for third

  10. Low-flow hydrology of the Sulphur Fork Red River basin, Robertson County, north-central Tennessee

    USGS Publications Warehouse

    Robbins, Clarence H.

    1979-01-01

    The objectives of this study were to define (1) the average 3-day natural low-flow with a 20-year recurrence interval for five low-flow partial-record sites and one continuous record station, (2) losing and gaining reaches of the main stem of the Sulphur Fork Red River and major tributaries, and (3) the quality of water during low-flow. An additional objective was the collection of continuous streamflow and temperature data at selected sites for development of a thermal model for use as a guide in design and management of a small reservoir. The quantity of surface water during low-flow varies considerably throughout the basin. Streamflow during periods of drought is groundwater discharging through numerous springs and seeps. The average 3-day, 20-year low-flow of the six study sites range from 0.1 to 2.2 cubic feet per second. Seepage investigations in October 1976 show that as much as 4.4 cubic feet per second are lost from the Sulphur Fork Red River within a reach of 1.7 miles between river mile 30.8 and 29.1. Seepage investigations in July 1977 show that as much as 3.7 cubic feet per second are gained in the Sulphur Fork Red River within a reach of 0.8 miles between river mile 42.6 and 41.8. Measured discharges from the 12 major springs in the basin ranged from less than 1 to 1660 gallons per minute during low-flow. Water quality of streams varies in time and space. Specific conductance ranged from 200 to 1,800 micromhos per centimeter at 25O centigrade during the 1976 seepage investigation on the Sulphur Fork Red River. During the two-year study the specific conductance of water from the springs ranged from 230 to 675 micromhos per centimeter at 25O centigrade.

  11. 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

  12. Low-flow transport models for conservative and sorbed solutes; Uvas Creek, near Morgan Hill, California

    USGS Publications Warehouse

    Jackman, A.P.; Walters, R.A.; Kennedy, V.C.

    1984-01-01

    Models describing low-flow transport of conservative (nonreactive) and reactive solutes, which adsorb on the streambed, are developed and tested. Temporary storage within the bed plays an important role in solute movement. Three different models of bed-storage processes are developed for conservative solutes. One model assumes the bed is a well-mixed, nondiffusing, nonreacting zone. Solute flux into the bed is then proportional to the difference between stream and bed-solute concentrations. A second model assumes that solute is transported within the bed by a vertical diffusion process. The bed-solute concentration, which matches the stream concentration at the interface, varies with depth in the bed according to Fick 's law. A third model assumes convection in the downstream direction occurs in certain parts of the bed, while the mechanism of the first model functions elsewhere. Storage of absorbing species is assumed to occur by equilibrium adsorption within streambed particles. Uptake rate is described by an intraparticle diffusion process. Model equations were solved using finite element numerical methods. Models were calibrated using data from a 24-hour injection of conservative chloride and adsorptive Sr ions at Uvas Creek near Morgan Hill, California. All models predict well except for some overestimation by the adsorption model during dieaway. (USGS)

  13. Subchannel thermal-hydraulic analysis at AP600 low-flow steam-line-break conditions

    SciTech Connect

    Morita, T.; Olson, C.A.; Sung, Y.X.; Connelley, J.F. Jr.; Novendstern, E.H.; Kapil, S.; Rosenthal, P.W.

    1995-12-01

    The AP600 reactor core approaches buoyancy-dominated flow at the departure from nucleate boiling (DNB)-limiting period of a postulated steam-line--break accident. The reactor core has a highly skewed power distribution at this time due to the conservative assumption of a withdrawn rod cluster control assembly (stuck rod). Under such conditions, strong buoyancy-induced core cross flow occurs, and coupled nuclear and thermal-hydraulic interactions become important. To analyze the transient, Westinghouse Electric Corporation has coupled THINC-IV with a neutronic code (ANC). Applicability of the THINC-IV subchannel code to the low-flow conditions with a steep radial power gradient is verified with existing rod bundle test results. The code predictions are in excellent agreement with the test data. The coupled codes provide a realistic three-dimensional simulation of core power by considering core flow distributions and the resultant enthalpy distributions in neutronic feedback. The safety analysis using the coupled code demonstrates that the DNB design basis is met during the postulated steam-line-break accident.

  14. 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)

  15. 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.

  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. 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.

  18. Panel regressions to estimate low-flow response to rainfall variability in ungaged basins

    NASA Astrophysics Data System (ADS)

    Bassiouni, Maoya; Vogel, Richard M.; Archfield, Stacey A.

    2016-12-01

    Multicollinearity and omitted-variable bias are major limitations to developing multiple linear regression models to estimate streamflow characteristics in ungaged areas and varying rainfall conditions. Panel regression is used to overcome limitations of traditional regression methods, and obtain reliable model coefficients, in particular to understand the elasticity of streamflow to rainfall. Using annual rainfall and selected basin characteristics at 86 gaged streams in the Hawaiian Islands, regional regression models for three stream classes were developed to estimate the annual low-flow duration discharges. Three panel-regression structures (random effects, fixed effects, and pooled) were compared to traditional regression methods, in which space is substituted for time. Results indicated that panel regression generally was able to reproduce the temporal behavior of streamflow and reduce the standard errors of model coefficients compared to traditional regression, even for models in which the unobserved heterogeneity between streams is significant and the variance inflation factor for rainfall is much greater than 10. This is because both spatial and temporal variability were better characterized in panel regression. In a case study, regional rainfall elasticities estimated from panel regressions were applied to ungaged basins on Maui, using available rainfall projections to estimate plausible changes in surface-water availability and usable stream habitat for native species. The presented panel-regression framework is shown to offer benefits over existing traditional hydrologic regression methods for developing robust regional relations to investigate streamflow response in a changing climate.

  19. Numerical Simulation of Cavitation in a Centrifugal Pump at Low Flow Rate

    NASA Astrophysics Data System (ADS)

    Tan, Lei; Cao, Shu-Liang; Wang, Yu-Ming; Zhu, Bao-Shan

    2012-01-01

    Based on the full cavitation model which adopts homogeneous flow supposition and considering the compressibility effect on cavitation flow to modify the re-normalization group k-in turbulence model by the density function, a computational model is developed to simulate cavitation flow of a centrifugal pump at low flow rate. The Navier-Stokes equation is solved with the SIMPLEC algorithm. The calculated curves of net positive suction head available (NPSHa) HNPSHa agree well with the experimental data. The critical point of cavitation in centrifugal pump can be predicted precisely, and the NPSH critical values derived from simulation are consistent with the experimental data. Thus the veracity and reliability of this computational model are verified. Based on the result of numerical simulation, the distribution of vapor volume fraction in the impeller and pressure at the impeller inlet are analyzed. Cavities first appear on the suction side of the blade head near the front shroud. A large number of cavities block the impeller channels, which leads to the sudden drop of head at the cavitation critical point. With the reduction of NPSHa, the distribution of pressure at the impeller inlet is more uniform.

  20. Assessment of low-flow, low-gradient aortic stenosis: multimodality imaging is the key to success.

    PubMed

    Clavel, Marie-Annick; Pibarot, Philippe

    2014-09-01

    In patients with aortic stenosis (AS), a low-flow state may occur with reduced LV ejection fraction (LVEF) (i.e., classic low flow) or with preserved LVEF (i.e., paradoxical low flow) and it is often associated with low gradient because the gradient is highly flow-dependent. Low-flow, low-gradient (LF-LG) AS is a frequent clinical entity generally associated with worse outcomes. A multimodality imaging approach, including comprehensive resting echocardiography, dobutamine stress echocardiography (DSE), and multidetector computed tomography (MDCT), is the key to successful management of patients with LF-LG AS, who represent a highly challenging subset from both a diagnostic and a therapeutic standpoint. DSE and quantification of aortic valve calcification by MDCT provide important information that is crucial to differentiate true-severe from pseudo-severe AS and therefore select the most appropriate therapy (i.e., AVR vs. medical). The assessment of LV flow reserve by DSE is useful to stratify the operative risk and guide decision making between surgical and transcatheter AVR. Other imaging biomarkers, such as the global LV longitudinal strain measured during DSE or the amount of myocardial fibrosis assessed by cardiac magnetic resonance imaging, may provide incremental information for risk stratification and therapeutic management in LF-LG AS, but additional studies are needed to validate and refine these emerging biomarkers further.

  1. 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.

  2. 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...

  3. 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

  4. Low-flow characteristics of streams in the Lahaina District, West Maui, Hawai'i

    USGS Publications Warehouse

    Cheng, Chui Ling

    2014-01-01

    The purpose of this study was to characterize streamflow availability under natural low-flow conditions for streams in the Lahaina District, west Maui, Hawaiʻi. The study-area streams included Honolua Stream and tributary Pāpua Gulch, Honokahua Stream and tributary Mokupeʻa Gulch, Kahana Stream, Honokōwai Stream and tributaries Amalu and Kapāloa Streams, Wahikuli Gulch and tributary Hāhākea Gulch, Kahoma Stream and tributary Kanahā Stream, Kauaʻula Stream, Launiupoko Stream, Olowalu Stream, and Ukumehame Gulch. The results of this study can be used to assist in the determination of technically defensible instream-flow standards for the study-area streams. Low-flow characteristics for natural (unregulated) streamflow conditions were represented by flow-duration discharges that are equaled or exceeded between 50 and 95 percent of the time. Partial-record sites were established on 10 main streams and 5 tributary streams, mainly upstream from existing surface-water diversions. Flow characteristics were determined using historical and current streamflow data from continuous-record streamflow-gaging stations and miscellaneous sites, and additional data collected as part of this study. Based on strategically scheduled observations, six of the study-area streams were ephemeral streams that were observed to remain dry at least 50 percent of the time: Pāpua Gulch, Honokahua Stream and its tributary Mokupeʻa Gulch, Kahana Stream, and Wahikuli Gulch and its tributary Hāhākea Gulch. For the remaining streams with measurable flow, Honolua, Honokōwai, Kahoma, Kanahā, Kauaʻula, Launiupoko, and Olowalu Streams, and Ukumehame Gulch, flow-duration discharges were computed for the 30-year base period (water years 1984–2013), using two record-augmentation techniques. The 95-percent flow-duration discharges ranged from 0 to 4.8 cubic feet per second (ft3/s). The 50-percent flow-duration discharges ranged from 0.47 to 9.5 ft3/s. This study also estimated the streamflow

  5. Pressure-volume curves in acute respiratory failure: automated low flow inflation versus occlusion.

    PubMed

    Servillo, G; Svantesson, C; Beydon, L; Roupie, E; Brochard, L; Lemaire, F; Jonson, B

    1997-05-01

    Pressure-volume (P-V) curves of the respiratory system allow determination of compliance and lower and upper inflection points (LIP and UIP, respectively). To minimize lung trauma in mechanical ventilation the tidal volume should be limited to the P-V range between LIP and UIP. An automated low flow inflation (ALFI) technique, using a computer-controlled Servo Ventilator 900C, was compared with a more conventional technique using a series of about 20 different inflated volumes (Pst-V curve). The pressure in the distal lung (Pdist) was calculated by subtraction of resistive pressure drop in connecting tubes and airways. Compliance (Cdist), Pdist(LIP), and Pdist(UIP) were derived from the Pdist-V curve and compared with Cst, Pst(LIP), and Pst(UIP) derived from the Pst-V curve. Nineteen sedated, paralyzed patients (10 with ARDS and 9 with ARF) were studied. We found: Cdist = 2.3 + 0.98 x Cst ml/cm H2O (r = 0.98); Pdist(LIP) = 0.013 + 1.09 x Pst(LIP) cm H2O (r = 0.96). In patients with ARDS: Pdist(UIP) = 4.71 + 0.84 x Pst(UIP) cm H2O (r = 0.94). In ARF, we found differences in UIP between the methods, but discrepancies occurred above tidal volumes and had little practical importance. They may reflect that Pdist comprises dynamic phenomena contributing to pressure in the distal lung at large volumes. Compliance, but not LIP and UIP, could be accurately determined without subtraction of resistive pressure from the pressure measured in the ventilator. We conclude that ALFI, which is fully automated and needing no ventilator disconnection, gives useful clinical information.

  6. 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.

  7. The relationship between snowpack and seasonal low flows in the Sierra Nevada: climate change and water availability in California

    NASA Astrophysics Data System (ADS)

    Godsey, S. E.; Kirchner, J. W.

    2004-12-01

    Seasonal low flows are important for sustaining aquatic ecosystems, and for supplying human needs during mid-summer. When the timing of water supply and demand do not coincide, humans rely on both natural and artificial storage. In California, the gap in timing between supply and demand is bridged primarily by the Sierra Nevada snowpack, which slowly melts throughout the spring and summer. However, most future climate scenarios suggest a decreased snowpack in the Sierra. Previous studies have investigated changes in snowmelt timing and spring snowmelt flood events. Here, by contrast, we explore how changes in the Sierra Nevada snowpack will affect annual low flows. We have identified all of the gauged catchments in the Sierra Nevada with unimpaired streamflow records and with at least ten years of overlapping snowpack and streamflow data. In each of these catchments, we have analyzed up to 40 years of historical snow and streamflow records. We find that annual minimum, mean, and maximum flows in these catchments all increase and decrease proportionally, or more-than-proportionally, as the annual peak snowpack water content changes from year to year. For every 10% decrease in snowpack, there is a 9-17% decrease in annual minimum flow. Minimum flows also occur earlier in years with smaller snowpacks; for every 10% decrease in snowpack, minimum flows occur 3-7 days earlier in the year. Finally, we find that in some catchments, annual low flows are significantly correlated not only with that year's snowpack, but with the previous year's snowpack as well. That is, seasonal low flows in some Sierra Nevada catchments exhibit a multi-year "memory" of snowmelt water inputs. We evaluate possible mechanisms that might underlie this observed memory effect. If these observed relationships between snow and flow hold in the future climate regime, the projected decrease in snowpack is likely to have a severe effect on seasonal low flows.

  8. 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...

  9. Conversion of Low-Flow Priapism to High-Flow State Using T-Shunt with Tunneling

    PubMed Central

    Tadros, Nicholas N.; Hedges, Jason C.

    2017-01-01

    Introduction. The three types of priapism are stuttering, arterial (high-flow, nonischemic), and venoocclusive (low-flow, ischemic). These are usually distinct entities and rarely occur in the same patient. T-shunts and other distal shunts are frequently combined with tunneling, but a seldom recognized potential complication is conversion to a high-flow state. Case Presentation. We describe 2 cases of men who presented with low-flow priapism episodes that were treated using T-shunts with tunneling that resulted with both men having recurrent erections shortly after surgery that were found to be consistent with high-flow states. Case 1 was a 33-year-old male with sickle cell anemia and case 2 was a 24-year-old male with idiopathic thrombocytopenic purpura. In both cases the men were observed over several weeks and both men returned to normal erectile function. Conclusions. Historically, proximal shunts were performed only in cases when distal shunts failed and carry a higher risk of serious complications. T-shunts and other distal shunts combined with tunneling are being used more frequently in place of proximal shunts. These cases illustrate how postoperative erections after T-shunts with tunneling can signify a conversion from low-flow to high-flow states and could potentially be misdiagnosed as an operative failure. PMID:28331646

  10. 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.

  11. 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

  12. 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

  13. Methods for estimating selected low-flow statistics and development of annual flow-duration statistics for Ohio

    USGS Publications Warehouse

    Koltun, G.F.; Kula, Stephanie P.

    2013-01-01

    This report presents the results of a study to develop methods for estimating selected low-flow statistics and for determining annual flow-duration statistics for Ohio streams. Regression techniques were used to develop equations for estimating 10-year recurrence-interval (10-percent annual-nonexceedance probability) low-flow yields, in cubic feet per second per square mile, with averaging periods of 1, 7, 30, and 90-day(s), and for estimating the yield corresponding to the long-term 80-percent duration flow. These equations, which estimate low-flow yields as a function of a streamflow-variability index, are based on previously published low-flow statistics for 79 long-term continuous-record streamgages with at least 10 years of data collected through water year 1997. When applied to the calibration dataset, average absolute percent errors for the regression equations ranged from 15.8 to 42.0 percent. The regression results have been incorporated into the U.S. Geological Survey (USGS) StreamStats application for Ohio (http://water.usgs.gov/osw/streamstats/ohio.html) in the form of a yield grid to facilitate estimation of the corresponding streamflow statistics in cubic feet per second. Logistic-regression equations also were developed and incorporated into the USGS StreamStats application for Ohio for selected low-flow statistics to help identify occurrences of zero-valued statistics. Quantiles of daily and 7-day mean streamflows were determined for annual and annual-seasonal (September–November) periods for each complete climatic year of streamflow-gaging station record for 110 selected streamflow-gaging stations with 20 or more years of record. The quantiles determined for each climatic year were the 99-, 98-, 95-, 90-, 80-, 75-, 70-, 60-, 50-, 40-, 30-, 25-, 20-, 10-, 5-, 2-, and 1-percent exceedance streamflows. Selected exceedance percentiles of the annual-exceedance percentiles were subsequently computed and tabulated to help facilitate consideration of the

  14. 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.

  15. 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.

  16. Low-flow CO2 removal integrated into a renal-replacement circuit can reduce acidosis and decrease vasopressor requirements

    PubMed Central

    2013-01-01

    Introduction Lung-protective ventilation in patients with ARDS and multiorgan failure, including renal failure, is often paralleled with a combined respiratory and metabolic acidosis. We assessed the effectiveness of a hollow-fiber gas exchanger integrated into a conventional renal-replacement circuit on CO2 removal, acidosis, and hemodynamics. Methods In ten ventilated critically ill patients with ARDS and AKI undergoing renal- and respiratory-replacement therapy, effects of low-flow CO2 removal on respiratory acidosis compensation were tested by using a hollow-fiber gas exchanger added to the renal-replacement circuit. This was an observational study on safety, CO2-removal capacity, effects on pH, ventilator settings, and hemodynamics. Results CO2 elimination in the low-flow circuit was safe and was well tolerated by all patients. After 4 hours of treatment, a mean reduction of 17.3 mm Hg (−28.1%) pCO2 was observed, in line with an increase in pH. In hemodynamically instable patients, low-flow CO2 elimination was paralleled by hemodynamic improvement, with an average reduction of vasopressors of 65% in five of six catecholamine-dependent patients during the first 24 hours. Conclusions Because no further catheters are needed, besides those for renal replacement, the implementation of a hollow-fiber gas exchanger in a renal circuit could be an attractive therapeutic tool with only a little additional trauma for patients with mild to moderate ARDS undergoing invasive ventilation with concomitant respiratory acidosis, as long as no severe oxygenation defects indicate ECMO therapy. PMID:23883472

  17. 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.

  18. Effect of dextran 500 on radial migration of erythrocytes in postcapillary venules at low flow rates.

    PubMed

    Kim, Sangho; Ong, Peng Kai; Johnson, Paul C

    2009-06-01

    Recently, we reported that collision efficiency (fraction of total collisions that result in the formation of aggregates) between red blood cells was an important factor in the formation of aggregates in postcapillary venules. In the present study, we focus on how high molecular weight dextran influences the overall radial migration trend of red blood cells in the postcapillary venule along a longitudinal distance of 50 microm from the bifurcation which would in turn affect collision behavior of these cells. A radial migration index, which defines the extent of radial migration of individual cells relative to the vessel center, was found to have a larger magnitude after infusion of dextran (1.9 +/- 2.73) compared to that before dextran infusion (1.48 +/- 3.89). This implied that dextran-induced aggregation might provide an external force to actively move cells towards the centerline of the vessel, which could contribute to the greater number of red blood cells participating in collision (16% increase) and aggregate formation. Further analysis of the collision behavior of individual red blood cells revealed that collision frequencies of individual cells decreased from a wide range (1 to 14) to a narrow range (1 to 5) after dextran treatment, indicating the alteration of collision behavior of red blood cells by the presence of aggregates along the flow stream.

  19. 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

    2016-07-19

    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.

  20. 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

  1. Low-flow water-quality and discharge data for lined channels in Northeast Albuquerque, New Mexico, 1990 to 1994

    USGS Publications Warehouse

    Gold, R.L.; McBreen, Robert

    1997-01-01

    The water resources of the Albuquerque metropolitan area are under increasing scrutiny by Federal and State regulators. Because of a lack of available low-flow data for use in addressing potential water-quality problems, a project was established to collect low-flow water-quality and discharge data. The project was initiated under a current cooperative program between the U.S. Geological Survey and the Albuquerque Metropolitan Arroyo Flood Control Authority. This report summarizes hydrologic data for that project collected between October 31, 1990, and September 3, 1994, at three sites in the lined channel network in northeast Albuquerque. The data collection network consisted of three sampling sites on Campus Wash, Embudo Arroyo, and the North Floodway Channel. The sites on Campus Wash and the North Floodway Channel were established at existing continuous-record streamflow-gaging stations; the Embudo Arroyo site was established at the site of an abandoned streamflow-gaging station. Data presented include site descriptions, instantaneous stream discharges measured at the time of sampling, and the results of the chemical analyses of the water-quality samples.

  2. 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.

  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. 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

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

    USGS Publications Warehouse

    Sprague, Lori A.; Nowell, Lisa 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.

  6. 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

  7. 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.

    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.

  8. 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.

  9. South Fork Shenandoah River habitat-flow modeling to determine ecological and recreational characteristics during low-flow periods

    USGS Publications Warehouse

    Krstolic, Jennifer L.; Ramey, R. Clay

    2012-01-01

    The ecological habitat requirements of aquatic organisms and recreational streamflow requirements of the South Fork Shenandoah River were investigated by the U.S. Geological Survey in cooperation with the Central Shenandoah Valley Planning District Commission, the Northern Shenandoah Valley Regional Commission, and Virginia Commonwealth University. Physical habitat simulation modeling was conducted to examine flow as a major determinant of physical habitat availability and recreation suitability using field-collected hydraulic habitat variables such as water depth, water velocity, and substrate characteristics. Fish habitat-suitability criteria specific to the South Fork Shenandoah River were developed for sub-adult and adult smallmouth bass (Micropterus dolomieu), juvenile and sub-adult redbreast sunfish (Lepomis auritus), spotfin or satinfin shiner (Cyprinella spp), margined madtom (Noturus insignis),and river chub (Nocomis micropogon). Historic streamflow statistics for the summer low-flow period during July, August, and September were used as benchmark low-flow conditions and compared to habitat simulation results and water-withdrawal scenarios based on 2005 withdrawal data. To examine habitat and recreation characteristics during droughts, daily fish habitat or recreation suitability values were simulated for 2002 and other selected drought years. Recreation suitability during droughts was extremely low, because the modeling demonstrated that suitable conditions occur when the streamflows are greater than the 50th percentile flow for July, August, and September. Habitat availability for fish is generally at a maximum when streamflows are between the 75th and 25th percentile flows for July, August, and September. Time-series results for drought years, such as 2002, showed that extreme low-flow conditions less than the 5th percentile of flow for July, August, and September corresponded to below-normal habitat availability for both game and nongame fish in the

  10. 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.

    2015-12-24

    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.

  11. Habitat use and movements of shovelnose sturgeon in Pool 13 of the upper Mississippi River during extreme low flow conditions

    USGS Publications Warehouse

    Curtis, Gary L.; Ramsey, John S.; Scarnecchia, Dennis L.

    1997-01-01

    We monitored habitat use and movement of 27 adult shovelnose sturgeon in Pool 13 of the upper Mississippi River, Iowa-Illinois, by radio-telemetry in April through August 1988. Our objective was to determine the response of this species to unusually low water conditions in the upper Mississippi River in 1988. Most (94%) telemetry contacts were made in 3 habitat types: main channel (50%), main channel border where wing dams were present (29%), and tailwaters of Lock and Dam 12 (15%). Habitat use in spring was affected by the extreme low flows. We often found tagged shovelnose sturgeon in the main channel and tailwaters during the spring period (11 March–20 May) where water velocities were highest. This was in contrast to other studies where shovelnose sturgeon did not occupy those areas during years with normal spring flows. Shovelnose sturgeon were typically found in areas with a sand bottom, mean water depth of 5.8 m, and mean bottom current velocity of 0.23 m sec-1. They occupied areas of swifter current but were not always found in the fastest current in their immediate vicinity. Tagged shovelnose sturgeon tended to remain in the upper, more riverine portion of the pool, and we observed no emigration from the study pool. Linear total range of movement from the tagging site ranged from 1.9 to 54.6 km during the study period.

  12. 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)

  13. 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

  14. Toxicity of chloride under winter low-flow conditions in an urban watershed in central Missouri, USA.

    PubMed

    Allert, Ann L; Cole-Neal, Cavelle L; Fairchild, James F

    2012-08-01

    Deicers such as sodium chloride and calcium chloride are used to treat snow and ice on road surfaces and have been identified as potential stressors on aquatic life. Hinkson Creek is an urban stream on the Missouri 303(d) list of impaired waters and is classified as impaired due to urban non-point source pollution. A 7-day toxicity test using Ceriodaphnia dubia was conducted to assess the toxicity of stream water during snowmelt at seven sites within the Hinkson Creek watershed. Chloride concentrations at two sites (Site 6, 1252 mg Cl/L; Site 4, 301 mg Cl/L) exceeded the U.S. Environmental Protection Agency chronic criterion (230 mg Cl/L). Survival (30 %) and total reproduction (6.9 young/adult) of C. dubia at Site 6 was significantly lower than survival (100 %) and total reproduction (30.4 young/adult) at Site 1 (reference site). Results indicate that chloride concentrations are elevated above water-quality criteria and that chloride may be a significant chemical stressor for macroinvertebrate communities during winter low-flow conditions in the Hinkson Creek watershed.

  15. Toxicity of chloride under winter low-flow conditions in an urban watershed in central Missouri, USA

    USGS Publications Warehouse

    Allert, Ann L.; Cole-Neal, Cavelle L.; Fairchild, James F.

    2012-01-01

    Deicers such as sodium chloride and calcium chloride are used to treat snow and ice on road surfaces and have been identified as potential stressors on aquatic life. Hinkson Creek is an urban stream on the Missouri 303(d) list of impaired waters and is classified as impaired due to urban non-point source pollution. A 7-day toxicity test using Ceriodaphnia dubia was conducted to assess the toxicity of stream water during snowmelt at seven sites within the Hinkson Creek watershed. Chloride concentrations at two sites (Site 6, 1252 mg Cl/L; Site 4, 301 mg Cl/L) exceeded the U.S. Environmental Protection Agency chronic criterion (230 mg Cl/L). Survival (30 %) and total reproduction (6.9 young/adult) of C. dubia at Site 6 was significantly lower than survival (100 %) and total reproduction (30.4 young/adult) at Site 1 (reference site). Results indicate that chloride concentrations are elevated above water-quality criteria and that chloride may be a significant chemical stressor for macroinvertebrate communities during winter low-flow conditions in the Hinkson Creek watershed.

  16. A survey on the use of low flow anaesthesia and the choice of inhalational anaesthetic agents among anaesthesiologists of India

    PubMed Central

    Amma, Rajasree Omanakutty; Ravindran, Subha; Koshy, Rachel Cherian; Jagathnath Krishna, KM

    2016-01-01

    Background and Aims: With the availability of modern workstations and heightened awareness on the environmental effects of waste anaesthesia gases, anaesthesiologists worldwide are practicing low flow anaesthesia (LFA). Although LFA is being practiced in India, hard evidence on the current practice of the same from anaesthesiologists practicing in India is lacking and hence, we conducted this survey. Methods: A questionnaire containing 16 questions was distributed among a subgroup of anaesthesiologists who attended the 2014 National Conference of Indian Society of Anaesthesiologists. The filled-in questionnaires were computed and analysed with SPSS version 11. Results: The response rate to the survey was 82%. About 73% of the respondents practiced LFA routinely, with 65% having workstations. Most of the anaesthesiologists used fresh gas flows <1.5 L/min with 45.1% using O2 concentrations at a range of 30–40%. ETCO2 monitoring was used routinely by most whereas use of agent analysers and bispectral index monitoring were restricted. The availability of scavenging system was also limited to only 33.5%. Majority preferred N2 O as carrier gas and sevoflurane as volatile agent of their choice. Conclusion: Our survey revealed that practice of LFA in India has numerous lacunae. Provision of better monitoring facilities, workstations as well as awareness regarding the environmental issues of waste anaesthetic gases need to be addressed. PMID:27761039

  17. 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).

  18. 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)

  19. 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

  20. Low-flow analysis and selected flow statistics representative of 1930-2002 for streamflow-gaging stations in or near West Virginia

    USGS Publications Warehouse

    Wiley, Jeffrey B.

    2006-01-01

    Five time periods between 1930 and 2002 are identified as having distinct patterns of annual minimum daily mean flows (minimum flows). Average minimum flows increased around 1970 at many streamflow-gaging stations in West Virginia. Before 1930, however, there might have been a period of minimum flows greater than any period identified between 1930 and 2002. The effects of climate variability are probably the principal causes of the differences among the five time periods. Comparisons of selected streamflow statistics are made between values computed for the five identified time periods and values computed for the 1930-2002 interval for 15 streamflow-gaging stations. The average difference between statistics computed for the five time periods and the 1930-2002 interval decreases with increasing magnitude of the low-flow statistic. The greatest individual-station absolute difference was 582.5 percent greater for the 7-day 10-year low flow computed for 1970-1979 compared to the value computed for 1930-2002. The hydrologically based low flows indicate approximately equal or smaller absolute differences than biologically based low flows. The average 1-day 3-year biologically based low flow (1B3) and 4-day 3-year biologically based low flow (4B3) are less than the average 1-day 10-year hydrologically based low flow (1Q10) and 7-day 10-year hydrologic-based low flow (7Q10) respectively, and range between 28.5 percent less and 13.6 percent greater. Seasonally, the average difference between low-flow statistics computed for the five time periods and 1930-2002 is not consistent between magnitudes of low-flow statistics, and the greatest difference is for the summer (July 1-September 30) and fall (October 1-December 31) for the same time period as the greatest difference determined in the annual analysis. The greatest average difference between 1B3 and 4B3 compared to 1Q10 and 7Q10, respectively, is in the spring (April 1-June 30), ranging between 11.6 and 102.3 percent

  1. Feasibility of a miniature centrifugal rotary blood pump for low-flow circulation in children and infants.

    PubMed

    Takatani, Setsuo; Hoshi, Hideo; Tajima, Kennichi; Ohuchi, Katsuhiro; Nakamura, Makoto; Asama, Junichio; Shimshi, Tadahiko; Yoshikawa, Masaharu

    2005-01-01

    In this study, a seal-less, tiny centrifugal rotary blood pump was designed for low-flow circulatory support in children and infants. The design was targeted to yield a compact and priming volume of 5 ml with a flow rate of 0.5-4 l/min against a head pressure of 40-100 mm Hg. To meet the design requirements, the first prototype had an impeller diameter of 30 mm with six straight vanes. The impeller was supported with a needle-type hydrodynamic bearing and was driven with a six-pole radial magnetic driver. The external pump dimensions included a pump head height of 20 mm, diameter of 49 mm, and priming volume of 5 ml. The weight was 150 g, including the motor driver. In the mock circulatory loop, using fresh porcine blood, the pump yielded a flow of 0.5-4.0 l/min against a head pressure of 40-100 mm Hg at a rotational speed of 1800-4000 rpm using 1/4" inflow and outflow conduits. The maximum flow and head pressure of 5.25 l/min and 244 mm Hg, respectively, were obtained at a rotational speed of 4400 rpm. The maximum electrical-to-hydraulic efficiency occurred at a flow rate of 1.5-3.5 l/min and at a rotational speed of 2000-4400 rpm. The normalized index of hemolysis, which was evaluated using fresh porcine blood, was 0.0076 g/100 l with the impeller in the down-mode and a bearing clearance of 0.1 mm. Further refinement in the bearing and magnetic coupler are required to improve the hemolytic performance of the pump. The durability of the needle-type hydrodynamic bearing and antithrombotic performance of the pump will be performed before clinical applications. The tiny centrifugal blood pump meets the flow requirements necessary to support the circulation of pediatric patients.

  2. An Analysis of the Effects and the Molecular Mechanism of Deep Hypothermic Low Flow on Brain Tissue in Mice

    PubMed Central

    Yang, Yuzhong

    2016-01-01

    Objectives: This study examined the effects and molecular mechanisms of deep hypothermic low flow (DHLF) on brain tissue in three genotypes of 3-week-old C57BL/6 mice (N = 180). Methods: Mice in the model condition were subjected to cerebral ischemia-reperfusion (I-R) while undergoing DHLF, then reperfused and rewarmed. Brain tissue damage was measured with 2,3,5-triphenyltetrazolium chloride (TTC) staining, and protein expression was measured by Western blot at 2 h, 24 h, and 72 h after treatment; messenger ribonucleic acid (mRNA) expressions were measured by real-time polymerase chain reaction (PCR) at 2 h, 24 h, and 72 h. Results: The expressions of p-Akt1 and p-GSK-3β were significantly higher in the model condition than the condition across genotypes, but both were significantly lower in the Akt1 mice. The expressions of Akt1 mRNA and Akt3 mRNA, but not Akt2 mRNA, were significantly higher in the model condition across genotypes. Brain damage was significantly greater in the Akt1 knockout gene mice compared with Akt2 gene knockout and wild type mice at 24 h and 72 h. Conclusion: These results suggest that the neuroprotective effects of DHLF reflect increased expression of p-GSK-3β induced through the PI3K/Akt signal pathway. Findings of real-time PCR imply that Akt1 mRNA and Akt3 mRNA may influence the expression of p-Akt1 and p-GSK-3β in mice undergoing DHLF. PMID:26961480

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

    USGS Publications Warehouse

    Ries, Kernell G.

    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.

  4. Chemical Gradients within Brain Extracellular Space Measured using Low Flow Push–Pull Perfusion Sampling in Vivo

    PubMed Central

    2012-01-01

    Although populations of neurons are known to vary on the micrometer scale, little is known about whether basal concentrations of neurotransmitters also vary on this scale. We used low-flow push–pull perfusion to test if such chemical gradients exist between several small brain nuclei. A miniaturized polyimide-encased push–pull probe was developed and used to measure basal neurotransmitter spatial gradients within brain of live animals with 0.004 mm3 resolution. We simultaneously measured dopamine (DA), norepinephrine, serotonin (5-HT), glutamate, γ-aminobutyric acid (GABA), aspartate (Asp), glycine (Gly), acetylcholine (ACh), and several neurotransmitter metabolites. Significant differences in basal concentrations between midbrain regions as little as 200 μm apart were observed. For example, dopamine in the ventral tegmental area (VTA) was 4.8 ± 1.5 nM but in the red nucleus was 0.5 ± 0.2 nM. Regions of high glutamate concentration and variability were found within the VTA of some individuals, suggesting hot spots of glutamatergic activity. Measurements were also made within the nucleus accumbens core and shell. Differences were not observed in dopamine and 5-HT in the core and shell; but their metabolites homovanillic acid (460 ± 60 nM and 130 ± 60 nM respectively) and 5-hydroxyindoleacetic acid (720 ± 200 nM and 220 ± 50 nM respectively) did differ significantly, suggesting differences in dopamine and 5-HT activity in these brain regions. Maintenance of these gradients depends upon a variety of mechanisms. Such gradients likely underlie highly localized effects of drugs and control of behavior that have been found using other techniques. PMID:23421683

  5. 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

  6. 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

  7. 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 augmentation.

  8. [A comparison of the effectiveness of transtracheal heating and humidification system in maintaining body temperature during general anesthesia with low flow gases].

    PubMed

    Matsuo, K; Honda, O; Hiraga, K; Yokokawa, Y

    2001-01-01

    We evaluated the effectiveness of transtracheal heating and humidification system in maintaining body temperature during general anesthesia with low flow gases in 12 gastric cancer patients. Patients were divided into two group; Control group A in which a hot-water circulating system was used and group B in which a transtracheal heating and humidification system by ANAMED HUMITUBE was used, during gastric cancer operation. Compared to the hot-water circulating system, the transtracheal heating and humidification system is more effective for maintaining body temperature and humidification after abdominal lavage by warm saline water. But there was no difference between the two groups about awakening from general anesthesia. We concluded that transtracheal heating and humidification system by ANAMED HUMITUBE is effective in maintaining body temperature under general anesthesia with low flow gases.

  9. 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.

  10. 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.

  11. 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.

  12. Blood warming, pump heating and haemolysis in low-flow extracorporeal life support; an in vitro study using freshly donated human blood.

    PubMed

    Kusters, R W J; Simons, A P; Lancé, M D; Ganushchak, Y M; Bekers, O; Weerwind, P W

    2017-01-01

    Low-flow extracorporeal life support can be used for cardiopulmonary support of paediatric and neonatal patients and is also emerging as a therapy for patients suffering from exacerbation of chronic obstructive pulmonary disease. However, pump heating and haemolysis have proven to negatively affect the system and outcome. This in vitro study aimed at gaining insight into blood warming, pump heating and haemolysis related to the performance of a new low-flow centrifugal pump. Pump performance in the 400-1,500 ml/min flow range was modulated using small-sized dual-lumen catheters and freshly donated human blood. Measurements included plasma free haemoglobin, blood temperature, pump speed, pump pressure, blood flow and thermographic imaging. Blood warming (ΔTmax=0.5°C) had no relationship with pump performance or haemolysis (R(2)max=0.05). Pump performance-related parameters revealed no relevant relationships with haemolysis (R(2)max=0.36). Thermography showed no relevant heat zones in the pump (Tmax=36°C). Concerning blood warming, pump heating and haemolysis, we deem the centrifugal pump applicable for low-flow extracorporeal circulation.

  13. 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

  14. Water-quality conditions during low flow in the lower Youghiogheny River basin, Pennsylvania, October 5-7, 1998

    USGS Publications Warehouse

    Sams, J. I.; Schroeder, K.T.; Ackman, T.E.; Crawford, J.K.; Otto, K.L.

    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 snapshot 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 minedischarge 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

  15. 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

  16. Review of low-flow bladder pump and high-volume air piston pump groundwater sampling systems at Sandia National Laboratories, New Mexico.

    SciTech Connect

    Collins, Sue S.; Jackson, Timmie Okchumpulla (Weston Solutions, Inc., Albuquerque, NM); Bailey, Glenn A.

    2003-01-01

    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

  17. Low-flow characteristics and flow-duration statistics for selected USGS continuous-record streamgaging stations in North Carolina through 2012

    USGS Publications Warehouse

    Weaver, J. Curtis

    2015-03-12

    In 2013, the U.S. Geological Survey, in cooperation with the North Carolina Division of Water Resources, compiled updated low-flow characteristics and flow-duration statistics for selected continuous-record streamgages in North Carolina. The compilation of updated streamflow statistics provides regulators and planners with relevant hydrologic information reflective of the recent droughts, which can be used to better manage the quantity and quality of streams in North Carolina. Streamflow records available through the 2012 water year1 were used to determine the annual (based on climatic year2) and winter 7-day, 10-year (7Q10, W7Q10) low-flow discharges, the 30-day, 2-year (30Q2) low-flow discharge, and the 7-day, 2-year (7Q2) low-flow discharge. Consequently, streamflow records available through March 31, 2012 (or the 2011 climatic year) were used to determine the updated low-flow characteristics. Low-flow characteristics were published for 177 unregulated sites, 56 regulated sites, and 33 sites known or considered to be affected by varying degrees of minor regulation and (or) diversions upstream from the streamgages (266 sites total). The updated 7Q10 discharges were compared for 63 streamgages across North Carolina where (1) long-term streamflow record consisted of 30 or more climatic years of data available as of the 1998 climatic year, and (2) streamflows were not known to be regulated. The 7Q10 discharges did not change for 3 sites, whereas increases and decreases were noted at 5 and 55 sites, respectively. Positive changes (increases) ranged from 4.3 percent (site 362) to 34.1 percent (site 112) with a median of 13.2 percent. Negative percentage changes (decreases) ranged from –3.3 percent (site 514) to –80.0 percent (site 308) with a median of –22.2 percent. The median percentage change for all 63 streamgages was –18.4 percent. Streamflow statistics determined as a part of this compilation included minimum, mean, maximum, and flow-duration statistics

  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. 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.; 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

  20. 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.

  1. Low-flow active and passive sampling of VOCs using thermal desorption tubes: theory and application at an offset printing facility.

    PubMed

    Batterman, Stuart; Metts, Tricia; Kalliokoski, Pentti; Barnett, Emily

    2002-06-01

    While air sampling techniques using adsorbent-based collection, thermal desorption and chromatographic analysis have found a niche in ambient air sampling, occupational applications have been more limited. This paper evaluates the use of thermal desorption techniques for low flow active and passive sampling configurations which allow conveniently long duration sampling in occupational settings and other high concentration environments. The use of an orifice enables flows as low as 0.5 ml min(-1) and sampling periods up to several days without significant biases. A model is used to predict sampling rates of a passive sampler encompassing an orifice, a void space, glass wool, and the adsorbent. Laboratory and field tests conducted at a commercial offset printing facility, which contained a variety of volatile organic compounds (primarily aromatic but also a few chlorinated and terpene compounds at levels from 1 to 67,000 microg m(-3)), are used to evaluate the approach. Tenax GR and Carbosieve SIII, both singly and together, were employed as adsorbents. Side-by-side tests comparing high flow, low flow and passive samplers show excellent agreement and high linearity (r = 0.95) for concentrations spanning nearly five orders of magnitude. Active samplers were tested at flows as low as 0.5 ml min(-1), compared to typical flows up to 40 ml min(-1). Passive samplers demonstrated a linear range and agreement with predictions for adsorbate loadings from approximately 1 ng to nearly 10 microg. Using a chemical mass balance receptor model, concentrations in the facility were apportioned to solvents, inks and other indoor and outdoor sources. Overall, the use of low flow active and passive sampling approaches employing thermal desorption techniques provides good performance and tremendous flexibility that facilitates use in many applications, including workplace settings.

  2. 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.

  3. Pharmacokinetics and outcome of tazobactam/piperacillin in Japanese patients undergoing low-flow continuous renal replacement therapy: dosage considerations

    PubMed Central

    Kohama, Hanako; Ide, Takeshi; Ikawa, Kazuro; Morikawa, Norifumi; Nishi, Shinichi

    2017-01-01

    Background Tazobactam/piperacillin (TAZ/PIPC), which is often combined with continuous renal replacement therapy (CRRT), induces renal excretion and is thought to have a high component removal rate for blood purification. CRRT procedures vary depending on the country, region, and institution. It is not clear whether the dose of TAZ/PIPC for use in Japan can be determined based on studies conducted in other countries. Therefore, in this study, we examined the suitability of recommended dose in Japan. Methods The study subjects consisted of 10 patients who received TAZ/PIPC during CRRT in the intensive care unit of Hyogo College of Medicine, Nishinomiya, Japan. We used a one-compartment model to characterize and parameterize the pharmacokinetics of TAZ/PIPC because their blood levels were eliminated monoexponentially. Results Compared with the data of healthy adults, the half-lives (t1/2) of both PIPC and TAZ were prolonged while their clearance rates decreased. Conclusion For the continuous hemodiafiltration procedure adopted in Japan, we concluded that the dose and frequency were appropriate because the patients who received PIPC/TAZ 2.25 g twice a day during continuous hemodiafiltration maintained appropriate blood levels of both PIPC and TAZ. PMID:28280397

  4. Natural and Diverted Low-Flow Duration Discharges for Streams Affected by the Waiahole Ditch System, Windward O`ahu, Hawai`i

    USGS Publications Warehouse

    Yeung, Chiu W.; Fontaine, Richard A.

    2007-01-01

    For nearly a century, the Waiahole Ditch System has diverted an average of approximately 27 million gallons per day of water from the wet, northeastern part of windward O`ahu, Hawai`i, to the dry, central part of the island to meet irrigation needs. The system intercepts large amounts of dike-impounded ground water at high altitudes (above approximately 700 to 800 ft) that previously discharged to Waiahole (and its tributaries Waianu and Uwao), Waikane, and Kahana Streams through seeps and springs. Diversion of this ground water has significantly diminished low flows in these streams. Estimates of natural and diverted flows are needed by water managers for (1) setting permanent instream flow standards to protect, enhance, and reestablish beneficial instream uses of water in the diverted streams and (2) allocating the diverted water for instream and offstream uses. Data collected before construction of the Waiahole Ditch System reflect natural (undiverted) flow conditions. Natural low-flow duration discharges for percentiles ranging from 50 to 99 percent were estimated for four sites at altitudes of 75 to 320 feet in Waiahole Stream (and its tributaries Waianu and Uwao Streams), for six sites at altitudes of 10 to 220 feet in Waikane Stream, and for three sites at altitudes of 30 to 80 feet in Kahana Stream. Among the available low-flow estimates along each affected stream, the highest natural Q50 (median) flows on Waiahole (altitude 250 ft), Waianu (altitude 75 ft), Waikane (altitude 75 ft), and Kahana Streams (altitude 30 ft) are 13, 7.0, 5.5, and 22 million gallons per day, respectively. Q50 (median) is just one of five duration percentiles presented in this report to quantify low-flow discharges. All flow-duration estimates were adjusted to a common period of 1960-2004 (called the base period). Natural flow-duration estimates compared favorably with limited pre-ditch streamflow data available for Waiahole and Kahana Streams. Data collected since construction of

  5. 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.

  6. A high sensitivity fiber optic macro-bend based gas flow rate transducer for low flow rates: theory, working principle, and static calibration.

    PubMed

    Schena, Emiliano; Saccomandi, Paola; Silvestri, Sergio

    2013-02-01

    A novel fiber optic macro-bend based gas flowmeter for low flow rates is presented. Theoretical analysis of the sensor working principle, design, and static calibration were performed. The measuring system consists of: an optical fiber, a light emitting diode (LED), a Quadrant position sensitive Detector (QD), and an analog electronic circuit for signal processing. The fiber tip undergoes a deflection in the flow, acting like a cantilever. The consequent displacement of light spot center is monitored by the QD generating four unbalanced photocurrents which are function of fiber tip position. The analog electronic circuit processes the photocurrents providing voltage signal proportional to light spot position. A circular target was placed on the fiber in order to increase the sensing surface. Sensor, tested in the measurement range up to 10 l min(-1), shows a discrimination threshold of 2 l min(-1), extremely low fluid dynamic resistance (0.17 Pa min l(-1)), and high sensitivity, also at low flow rates (i.e., 33 mV min l(-1) up to 4 l min(-1) and 98 mV min l(-1) from 4 l min(-1) up to 10 l min(-1)). Experimental results agree with the theoretical predictions. The high sensitivity, along with the reduced dimension and negligible pressure drop, makes the proposed transducer suitable for medical applications in neonatal ventilation.

  7. A high sensitivity fiber optic macro-bend based gas flow rate transducer for low flow rates: Theory, working principle, and static calibration

    NASA Astrophysics Data System (ADS)

    Schena, Emiliano; Saccomandi, Paola; Silvestri, Sergio

    2013-02-01

    A novel fiber optic macro-bend based gas flowmeter for low flow rates is presented. Theoretical analysis of the sensor working principle, design, and static calibration were performed. The measuring system consists of: an optical fiber, a light emitting diode (LED), a Quadrant position sensitive Detector (QD), and an analog electronic circuit for signal processing. The fiber tip undergoes a deflection in the flow, acting like a cantilever. The consequent displacement of light spot center is monitored by the QD generating four unbalanced photocurrents which are function of fiber tip position. The analog electronic circuit processes the photocurrents providing voltage signal proportional to light spot position. A circular target was placed on the fiber in order to increase the sensing surface. Sensor, tested in the measurement range up to 10 l min-1, shows a discrimination threshold of 2 l min-1, extremely low fluid dynamic resistance (0.17 Pa min l-1), and high sensitivity, also at low flow rates (i.e., 33 mV min l-1 up to 4 l min-1 and 98 mV min l-1 from 4 l min-1 up to 10 l min-1). Experimental results agree with the theoretical predictions. The high sensitivity, along with the reduced dimension and negligible pressure drop, makes the proposed transducer suitable for medical applications in neonatal ventilation.

  8. A high sensitivity fiber optic macro-bend based gas flow rate transducer for low flow rates: Theory, working principle, and static calibration

    SciTech Connect

    Schena, Emiliano; Saccomandi, Paola; Silvestri, Sergio

    2013-02-15

    A novel fiber optic macro-bend based gas flowmeter for low flow rates is presented. Theoretical analysis of the sensor working principle, design, and static calibration were performed. The measuring system consists of: an optical fiber, a light emitting diode (LED), a Quadrant position sensitive Detector (QD), and an analog electronic circuit for signal processing. The fiber tip undergoes a deflection in the flow, acting like a cantilever. The consequent displacement of light spot center is monitored by the QD generating four unbalanced photocurrents which are function of fiber tip position. The analog electronic circuit processes the photocurrents providing voltage signal proportional to light spot position. A circular target was placed on the fiber in order to increase the sensing surface. Sensor, tested in the measurement range up to 10 l min{sup -1}, shows a discrimination threshold of 2 l min{sup -1}, extremely low fluid dynamic resistance (0.17 Pa min l{sup -1}), and high sensitivity, also at low flow rates (i.e., 33 mV min l{sup -1} up to 4 l min{sup -1} and 98 mV min l{sup -1} from 4 l min{sup -1} up to 10 l min{sup -1}). Experimental results agree with the theoretical predictions. The high sensitivity, along with the reduced dimension and negligible pressure drop, makes the proposed transducer suitable for medical applications in neonatal ventilation.

  9. 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.

  10. Significant lung volume reduction with endobronchial valves in a patient despite the presence of microcollaterals masked by low-flow Chartis phenotype

    PubMed Central

    Yin, Yan; Hou, Gang; Herth, Felix J; Wang, Xiao-bo; Wang, Qiu-yue; Kang, Jian

    2016-01-01

    Satisfactory functional outcomes following bronchoscopic lung volume reduction (BLVR) using endobronchial valves (EBVs) depend on the absence of collateral ventilation (CV) between the target and adjunct lobes. The Chartis system has proven to be useful for determining whether CV is present or absent, but this system can also erroneously indicate the absence of CV, which can lead to BLVR failure. Here, we describe low-flow Chartis phenotype in the target lobe resulted in difficult judgment of existence of CV. Consequently, BLVR with EBVs implanted into the right upper bronchus failed to reduce lung volume or induce atelectasis. Inserting another EBV into the right middle bronchus blocked the latent CV, which led to significant lung volume reduction in the right upper lobe (RUL) and right middle lobe (RML) and to improve the pulmonary function, 6-min walking distance, and St George respiratory questionnaire scores over a 2-week follow-up period. Low flow in the target lobe is a unique Chartis phenotype and represents the uncertainty of CV, which is a risk factor for the failure of BLVR using EBVs. Clinicians should be aware of this possibility and might be able to resolve the problem by blocking the RUL and RML between which the CV occurs. PMID:27920518

  11. 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

  12. Stream-water quality during storm-runoff events and low-flow periods in the St. Clair River/Lake St. Clair Basin, Michigan

    USGS Publications Warehouse

    Weaver, Thomas L.; Fuller, Lori M.

    2007-01-01

    This report, a product of the Lake St. Clair Regional Monitoring Project, describes four water-quality studies in the St. Clair River/Lake St. Clair Basin from the early 1970's through 2005. All the studies examined water quality of streams in the basin; the most recent studies focused primarily on water quality during high- and low-streamflows. This report explains how storm-runoff and low-flow periods affect water quality in the basin. Included is a summary of stream-water quality findings from the National Stream Quality Accounting Network (1973-95); the National Water-Quality Assessment (1996-98); the Oakland County Land-Use Change study (2001-03); and the Lake St. Clair Regional Monitoring Project (2004-05).

  13. 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

  14. 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

  15. 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

  16. CFD Analysis for Flow Behavior Characteristics in the Upper Plenum during low flow/low pressure transients for the Gas Cooled Fast Reactor (GCFR)

    SciTech Connect

    Piyush Sabharwall; Theron Marshall; Kevan Weaver; Hans Gougar

    2007-05-01

    Gas coolant at low pressure exhibits poor heat transfer characteristics. This is an area of concern for the passive response targeted by the Generation IV GCFR design. For the first 24 hour period, the decay heat removal for the GCFR design is dependent on an actively powered blower, which also would reduce the temperature in the fuel during transients, before depending on the passive operation. Natural circulation cooling initiates when the blower is stopped for the final phase of the decay heat removal, as under forced convection the core decay heat is adequately cooled by the running blower. The ability of the coolant to flow in the reverse direction or having recirculation, when the blowers are off, necessitates more understanding of the flow behavior characteristics in the upper plenum. The work done here focuses primarily on the period after the blower has been turned off, as the core is adequately cooled when the blowers are running, thus there was no need to carry out the analysis for the first 24 hours. In order to understand the plume behavior for the GCFR upper plenum several cases were run, with air, helium and helium-air mixture. For each case, the FLUENT was used to characterize the steady state velocity vectors and corresponding temperature in the upper plenum under passive decay heat removal conditions. This study will provide better insight into the plume interaction in the upper plenum at low flow and low pressure conditions.

  17. 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.

  18. 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)

  19. Stress echocardiography to assess stenosis severity and predict outcome in patients with paradoxical low-flow, low-gradient aortic stenosis and preserved LVEF.

    PubMed

    Clavel, Marie-Annick; Ennezat, Pierre Vladimir; Maréchaux, Sylvestre; Dumesnil, Jean G; Capoulade, Romain; Hachicha, Zeineb; Mathieu, Patrick; Bellouin, Annaïk; Bergeron, Sébastien; Meimoun, Patrick; Arsenault, Marie; Le Tourneau, Thierry; Pasquet, Agnès; Couture, Christian; Pibarot, Philippe

    2013-02-01

    The objective of this study was to examine the value of stress-echocardiography in patients with paradoxical low-flow, low-gradient (PLFLG) aortic stenosis (AS). The projected aortic valve area (AVAProj) at a normal flow rate was calculated in 55 patients with PLFLG AS. In the subset of patients (n = 13) who underwent an aortic valve replacement within 3 months after stress echocardiography, AVA(Proj) correlated better with the valve weight compared to traditional resting and stress echocardiographic parameters of AS severity (AVA(Proj): r = -0.78 vs. other parameters: r = 0.46 to 0.56). In the whole group (N = 55), 18 (33%) patients had an AVA(Proj) >1.0 cm(2), being consistent with the presence of pseudo severe AS. The AVA(Proj) was also superior to traditional parameters of stenosis severity for predicting outcomes (hazard ratio: 1.32/0.1 cm(2) decrease in AVA(Proj)). In patients with PLFLG AS, the measurement of AVA(proj) derived from stress echocardiography is helpful to determine the actual severity of the stenosis and predict risk of adverse events.

  20. 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)

  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. 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.

  3. 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.

  4. The role of river sediments in contamination storage downstream of a waste water treatment plant in low flow conditions: Organotins, faecal indicator bacteria and nutrients

    NASA Astrophysics Data System (ADS)

    Chahinian, N.; Bancon-Montigny, C.; Caro, A.; Got, P.; Perrin, J. L.; Rosain, D.; Rodier, C.; Picot, B.; Tournoud, M. G.

    2012-12-01

    In intermittent rivers, characterised by a specific hydrological behaviour, sediment-water column interactions may influence water quality during low flows. The main objective of this work was to assess the extent of anthropogenic pollution (organotins, faecal indicator bacteria and nutrients) in the river sediment of an intermittent river and its impact on the downstream water bodies: The Vène River, main tributary of the Thau lagoon. We first investigated anthropogenic pollution from water and sediment samples collected in situ along the river course (1.5 km); then, during laboratory experiments, we assessed the survival of faecal bacteria and quantified the degradation rates of organotins on the same sediments. The results indicate the presence of anthropogenic pollution all along the study reach. The waste water treatment plant effluent is a direct pollution input source for anthropogenic pollution. The sediment data points to an urban drainage ditch as a secondary point pollution source while the organotins data highlights the presence of other diffuse sources, specific to this substance. The results of the laboratory experiments show that both faecal bacteria and organotins may persist in the river sediments for up to two months in summer and even longer in winter. This indicates that sediments may, under favourable conditions, become important pollutant stores which may later be released and transported to the Thau lagoon during floods.

  5. Low-flow characteristics for streams on the Islands of Kauaʻi, Oʻahu, Molokaʻi, Maui, and Hawaiʻi, State of Hawaiʻi

    USGS Publications Warehouse

    Cheng, Chui Ling

    2016-08-03

    Statistical models were developed to estimate natural streamflow under low-flow conditions for streams with existing streamflow data at measurement sites on the Islands of Kauaʻi, Oʻahu, Molokaʻi, Maui, and Hawaiʻi. Streamflow statistics used to describe the low-flow characteristics are flow-duration discharges that are equaled or exceeded between 50 and 95 percent of the time during the 30-year base period 1984–2013. Record-augmentation techniques were applied to develop statistical models relating concurrent streamflow data at the measurement sites and long-term data from nearby continuous-record streamflow-gaging stations that were in operation during the base period and were selected as index stations. Existing data and subsequent low-flow analyses of the available data help to identify streams in under-represented geographic areas and hydrogeologic settings where additional data collection is suggested.Low-flow duration discharges were estimated for 107 measurement sites (including long-term and short-term continuous-record streamflow-gaging stations, and partial-record stations) and 27 index stations. The adequacy of statistical models was evaluated with correlation coefficients and modified Nash-Sutcliff coefficients of efficiency, and a majority of the low-flow duration-discharge estimates are satisfactory based on these regression statistics.Molokaʻi and Hawaiʻi have the fewest number of measurement sites (that are not located on ephemeral stream reaches) at which flow-duration discharges were estimated, which can be partially explained by the limited number of index stations available on these islands that could be used for record augmentation. At measurement sites on some tributary streams, low-flow duration discharges could not be estimated because no adequate correlations could be developed with the index stations. These measurement sites are located on streams where duration-discharge estimates are available at long-term stations at other

  6. 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

  7. 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

  8. Low-flow characteristics of streams under natural and diversion conditions, Waipiʻo Valley, Island of Hawaiʻi, Hawaiʻi

    USGS Publications Warehouse

    Fontaine, Richard A.

    2012-01-01

    Over the past 100 years, natural streamflow in Waipiʻo Valley has been reduced by the transfer of water out of the valley by Upper and Lower Hāmākua Ditches. The physical condition and diversion practices along the two ditch systems have varied widely over the years, and as a result, so have their effects on natural streamflow in Waipiʻo Valley. Recent renovation and improvements to Lower Hāmākua Ditch system, along with proposals for its future operation and water-diversion strategies, have unknown implications. The purpose of this report is to quantify the availability of streamflow and to determine the effects of current and proposed diversion strategies on the low-flow hydrology in Waipiʻo Valley. In this report, the low-flow hydrology of Waipiʻo Valley is described in terms of flow-duration statistics. Flow-duration statistics were computed for three locations in the Waipiʻo Valley study area where long-term surface-water gaging stations have been operated. Using a variety of streamflow record-extension techniques, flow-duration statistics were estimated at an additional 13 locations where only few historical data are available or where discharge measurements were made as part of this study. Flow-duration statistics were computed to reflect natural conditions, current (2000-2005) diversion conditions, and proposed future diversion conditions at the 16 locations. At the downstream limit of the study area, on Wailoa Stream at an altitude of 190 feet, a baseline for evaluating the availability of streamflow is provided by computed flow-duration statistics that are representative of natural, no-diversion conditions. At the Wailoa gaging station, 95- and 50-percentile discharges under natural conditions were determined to be 86 and 112 cubic feet per second, respectively. Under 1965-1969 diversion conditions, natural 95- and 50-percentile discharges were reduced by 52 and 53 percent, to 41 and 53 cubic feet per second, respectively. Under current (2000

  9. Traveltime, reaeration, and water-quality characteristics during low-flow conditions in Wilsons Creek and the James River near Springfield, Missouri

    USGS Publications Warehouse

    Berkas, W.R.

    1987-01-01

    Before upgrading the Southwest Wastewater-Treatment Plant near Springfield, Missouri, to tertiary treatment, adverse water quality conditions resulting from discharge of wastewater effluent to Wilson Creek were documented in the creek and in the James River. About 7 years after the upgrading of the treatment plant, traveltime, reaeration, and water quality characteristics were determined in Wilsons Creek and the James River. Traveltime was measured once in Wilsons Creek and twice in the James River during low-flow conditions. Traveltimes in the James River were estimated for discharge between 55 and 200 cu ft/sec at a site near Boaz. Reaeration coefficients were calculated for five reaches in Wilsons Creek and the James River using the modified-tracer technique. Calculated reaeration coefficients were compared with coefficients predicted by twelve empirical equations and one equation was chosen that best fit the data. Water quality data were collected during two 44-hr periods, August 14 to 16, 1984, and July 23 to 25, 1985. Samples were collected at the outflow of the Southwest Wastewater Treatment Plant at seven sites along Wilsons Creek and the James River. Dissolved-oxygen concentrations in Wilsons Creek and the James River were all larger than Missouri 's water quality standard of 5.0 mg/l. Ammonia concentrations and 5-day carbonaceous biochemical oxygen demands were small, which indicated that the oxygen consumption by oxidizing ammonia and carbonaceous organic materials would be insignificant. Measured streambed oxygen demand in the James River was largest directly downstream from Wilsons Creek. (USGS)

  10. 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.

  11. 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.

  12. Phosphorus and E. coli in the Fanno and Bronson Creek subbasins of the Tualatin River basin, Oregon, during summer low-flow conditions, 1996

    USGS Publications Warehouse

    McCarthy, Kathleen A.

    2000-01-01

    probably due to sources such as domestic pet and wildlife waste, failing septic systems, or improperly managed hobby farms. The data did not indicate any large breaks in sewer lines or other large-scale sources of bacterial contamination to surface water in either subbasin during this low-flow period.

  13. 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, Narong

    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 ~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 ~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 of signal for even the most

  14. 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.

  15. Frequency and intensity of extreme drought in the Delaware Basin, 1600-2002

    NASA Astrophysics Data System (ADS)

    Kauffman, G. J.; Vonck, K. J.

    2011-05-01

    The frequency and severity of drought in the Delaware Basin between 1600 and 2002 are examined using the Palmer Drought Severity Index (PDSI) estimated from tree ring data and correlated with reconstructed annual low flows. In the Delaware Basin, the most severe drought in nearly a century occurred during 1995-2002 as the Brandywine River, Delaware's largest surface water supply, ran dry at its mouth and declined to the lowest flow on record since 1912. To evaluate the long-term context of the 1995-2002 droughts given a variable hydroclimate, tree ring and PDSI data were correlated to reconstruct flows along the river to 1600, the beginning of European exploration to the Delaware Bay. Reconstructed PDSI and low flows were fit using general extreme value (GEV) distributions to estimate drought frequency. Some variability is present as reconstructed low flows tend to overestimate recorded streamflow in severe dry years, a finding reported by others. Some uncertainty appears in the correlations as the coefficient of multiple determination (CRSQ) between recorded and estimated PDSI from tree ring data is 0.50-0.54, a level of variance considered to be "quite good," and the coefficient of determination (r2) between PDSI and low flow is 0.52. Given the uncertainty, PDSI and reconstructed low flow data both agree that the most extreme drought in 400 years occurred during 1635, and the drought of 1995-2000 was historically extreme with differences only in the degree of severity. On the basis of PDSI, the 2002, 1999, and 1995 droughts were the sixth, twelfth, and seventeenth most severe in 400 years with frequencies of once every 50, 33, and 16 years, respectively. Based on low flow, the 2002, 1999, and 1995 droughts were the second, fourth, and ninth most severe since 1600 with frequencies of once every 200, 100, and 50 years, respectively. The record drought of 2002 has a low probability of reoccurring in any given year (2.0% by PDSI and 0.5% by low flow), but droughts

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. Frequency Comb Cooling Project

    DTIC Science & Technology

    2014-03-18

    frequency combs ). Recently the power and spectral coverage of frequency combs have grown considerably with projected 1. REPORT DATE (DD-MM-YYYY) 4. TITLE...Aug-2011 18-May-2012 Approved for Public Release; Distribution Unlimited Final report on frequency comb cooling project The views, opinions and/or... frequency combs ). Recently the power and spectral coverage of frequency combs have grown considerably with projected average powers above 10 kW. We

  2. 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.

  3. DDC Descriptor Frequencies.

    ERIC Educational Resources Information Center

    Klingbiel, Paul H.; Jacobs, Charles R.

    This report summarizes the frequency of use of the 7144 descriptors used for indexing technical reports in the Defense Documentation Center (DDC) collection. The descriptors are arranged alphabetically in the first section and by frequency in the second section. The frequency data cover about 427,000 AD documents spanning the interval from March…

  4. 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.

  5. 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.…

  6. 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.

  7. 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.

  8. Frequency selective infrared sensors

    SciTech Connect

    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.

  9. 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

  10. Radio frequency spectrum management

    NASA Astrophysics Data System (ADS)

    Sujdak, E. J., Jr.

    1980-03-01

    This thesis is a study of radio frequency spectrum management as practiced by agencies and departments of the Federal Government. After a brief introduction to the international agency involved in radio frequency spectrum management, the author concentrates on Federal agencies engaged in frequency management. These agencies include the National Telecommunications and Information Administration (NTIA), the Interdepartment Radio Advisory Committee (IRAC), and the Department of Defense (DoD). Based on an analysis of Department of Defense frequency assignment procedures, recommendations are given concerning decentralizing military frequency assignment by delegating broader authority to unified commanders. This proposal includes a recommendation to colocate the individual Service frequency management offices at the Washington level. This would result in reduced travel costs, lower manpower requirements, and a common tri-Service frequency management data base.

  11. 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.

  12. Cooled Ion Frequency Standard

    DTIC Science & Technology

    1988-09-27

    on Frequency Standards and Metrology, Ancona , Italy (Springer Verlag, 1988) to be published. 8. "High Accuracy Spectroscopy of Stored Ions," D.J...Wineland, W.M. Itano, J.S. Bergquist, J.J. Bollinger, F. Diedrich and S.L. Gilbert, Proc. 4th Symp. on Frequency Standards and Metrology, Ancona , Italy...Proc. 4th Symp. on Frequency Standards and Metrology, Ancona , Italy (Springer Verlag, 1988) to be published. 10. "Quantative Study of Laser Cooling in

  13. Multi-Frequency Synthesis

    NASA Astrophysics Data System (ADS)

    Sault, R. J.; Conway, J. E.

    Multi-frequency synthesis is the practice of using visibility data measured over a range of frequencies when forming a continuum image. Because observing frequency is easier to vary than antenna location, it is an effective way of filling the (u,v) plane for an observation. Here we consider the artifacts in MFS images caused by source spectral variation. For frequency ranges of about 30%, for observations where only modest dynamic range is required, the artifacts of MFS can be completely ignored. For higher dynamic range observations, some calibration techniques and deconvolution algorithms are described which minimize the artifacts.

  14. Frequency Response Analysis Tool

    SciTech Connect

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

    2014-12-01

    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.

  15. 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.

  16. 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

  17. 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.

  18. Multi-Frequency Synthesis

    NASA Astrophysics Data System (ADS)

    Conway, J. E.; Sault, R. J.

    Introduction; Image Fidelity; Multi-Frequency Synthesis; Spectral Effects; The Spectral Expansion; Spectral Dirty Beams; First Order Spectral Errors; Second Order Spectral Errors; The MFS Deconvolution Problem; Nature of The Problem; Map and Stack; Direct Assault; Data Weighting Methods; Double Deconvolution; The Sault Algorithm; Multi-Frequency Self-Calibration; Practical MFS; Conclusions

  19. 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.

  20. 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.

  1. Frequency Diverse Array Radar

    DTIC Science & Technology

    2010-09-01

    the methods for electronic scanning of antenna systems. Techniques that have been studied in this connection include frequency variation, phase shift...an array antenna instantaneously into a desired direction where no mechanical mechanism is involved in the scanning process. Electronic scanning... methods including phase scanning, time delay scanning, and frequency scanning have been used in various radar applications; however new and cheaper

  2. 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.

  3. Frequency comb swept lasers

    PubMed Central

    Tsai, Tsung-Han; Zhou, Chao; Adler, Desmond C.; Fujimoto, James G.

    2010-01-01

    We demonstrate a frequency comb (FC) swept laser and a frequency comb Fourier domain mode locked (FC-FDML) laser for applications in optical coherence tomography (OCT). The fiber-based FC swept lasers operate at a sweep rate of 1kHz and 120kHz, respectively over a 135nm tuning range centered at 1310nm with average output powers of 50mW. A 25GHz free spectral range frequency comb filter in the swept lasers causes the lasers to generate a series of well defined frequency steps. The narrow bandwidth (0.015nm) of the frequency comb filter enables a ~−1.2dB sensitivity roll off over ~3mm range, compared to conventional swept source and FDML lasers which have −10dB and −5dB roll offs, respectively. Measurements at very long ranges are possible with minimal sensitivity loss, however reflections from outside the principal measurement range of 0–3mm appear aliased back into the principal range. In addition, the frequency comb output from the lasers are equally spaced in frequency (linear in k-space). The filtered laser output can be used to self-clock the OCT interference signal sampling, enabling direct fast Fourier transformation of the fringe signals, without the need for fringe recalibration procedures. The design and operation principles of FC swept lasers are discussed and designs for short cavity lasers for OCT and interferometric measurement applications are proposed. PMID:19997365

  4. Precision optical reference frequencies

    NASA Astrophysics Data System (ADS)

    Riehle, Fritz; Schnatz, Harald; Zinner, G.; Trebst, Tilmann; Helmcke, Juergen

    1999-05-01

    Optical reference frequencies are provided by lasers of which the frequencies are stabilized to suitable absorption lines. Presently, twelve reference frequencies/wavelengths within the wavelengths range from 243 nm to 10.3 micrometers are recommended by the International Committee of Weights and Measures as references for the realization of the meter and scientific applications. As typical examples, we describe a diode-pumped, frequency doubled YAG-laser stabilized to an absorption line of molecular iodine and a Ca-stabilized laser. The latter one has been developed in two versions, a transportable system utilizing a small beam of thermal Ca atoms and a stationary standard based on laser cooled and trapped Ca atoms. The frequency of the Ca standard based on cold Ca atoms has been measured by a frequency chain allowing a phase-coherent comparison against the primary standard of time and frequency, the caesium clock. Its value is vCa equals 455 986 240 494.13 kHz with a relative standard uncertainty of 2.5 (DOT) 10-13.

  5. Frequency comb swept lasers.

    PubMed

    Tsai, Tsung-Han; Zhou, Chao; Adler, Desmond C; Fujimoto, James G

    2009-11-09

    We demonstrate a frequency comb (FC) swept laser and a frequency comb Fourier domain mode locked (FC-FDML) laser for applications in optical coherence tomography (OCT). The fiber-based FC swept lasers operate at a sweep rate of 1kHz and 120kHz, respectively over a 135nm tuning range centered at 1310nm with average output powers of 50mW. A 25GHz free spectral range frequency comb filter in the swept lasers causes the lasers to generate a series of well defined frequency steps. The narrow bandwidth (0.015nm) of the frequency comb filter enables a approximately -1.2dB sensitivity roll off over approximately 3mm range, compared to conventional swept source and FDML lasers which have -10dB and -5dB roll offs, respectively. Measurements at very long ranges are possible with minimal sensitivity loss, however reflections from outside the principal measurement range of 0-3mm appear aliased back into the principal range. In addition, the frequency comb output from the lasers are equally spaced in frequency (linear in k-space). The filtered laser output can be used to self-clock the OCT interference signal sampling, enabling direct fast Fourier transformation of the fringe signals, without the need for fringe recalibration procedures. The design and operation principles of FC swept lasers are discussed and designs for short cavity lasers for OCT and interferometric measurement applications are proposed.

  6. The Humidity in a Low-Flow Dräger Fabius Anesthesia Workstation with or without Thermal Insulation or a Heat and Moisture Exchanger: A Prospective Randomized Clinical Trial

    PubMed Central

    de Oliveira, Sergius A. R.; Lucio, Lorena M. C.; Modolo, Norma S. P.; Hayashi, Yoko; Braz, Mariana G.; de Carvalho, Lídia R.; Braz, Leandro G.; Braz, José Reinaldo C.

    2017-01-01

    Background During anesthesia, as compared with intensive care, the time of the tracheal intubation is much shorter. An inhaled gas minimum humidity of 20 mgH2O.L-1 is recommended to reduce the deleterious effects of dry gas on the airways during anesthesia with tracheal intubation. The Fabius GS Premium® anesthesia workstation (Dräger Medical, Lübeck, Germany) has a built-in hotplate to heat gases in the breathing circuit. A heat and moisture exchanger (HME) is used to further heat and humidify the inhaled gas. The humidity of the gases in the breathing circuit is influenced by the ambient temperature. We compared the humidity of the inhaled gases from a low-flow Fabius anesthesia workstation with or without thermal insulation (TI) of the breathing circuit and with or without an HME. Methods We conducted a prospective randomized trial in 41 adult female patients who underwent elective abdominal surgery. The patients were allocated into four groups according to the devices used to ventilate their lungs using a Dräger Fabius anesthesia workstation with a low gas flow (1 L.min-1): control, with TI, with an HME or with TI and an HME (TIHME). The mean temperature and humidity of the inhaled gases were measured during 2-h after connecting the patients to the breathing circuit. Results The mean inhaled gas temperature and absolute humidity were higher in the HME (29.2±1.3°C; 28.1±2.3 mgH2O·L-1) and TIHME (30.1±1.2°C; 29.4±2.0 mgH2O·L-1) groups compared with the control (27.5±1.0°C; 25.0±1.8 mgH2O·L-1) and TI (27.2±1.1°C; 24.9±1.8 mgH2O·L-1) groups (P = 0.003 and P<0.001, respectively). Conclusions The low-flow Fabius GS Premium breathing circuit provides the minimum humidity level of inhaled gases to avoid damage to the tracheobronchial epithelia during anesthesia. TI of the breathing circuit does not increase the humidity of the inhaled gases, whereas inserting an HME increases the moisture of the inhaled gases closer to physiological values. PMID

  7. Radio frequency strain monitor

    NASA Technical Reports Server (NTRS)

    Heyman, Joseph S. (Inventor); Rogowski, Robert S. (Inventor); Holben, Jr., Milford S. (Inventor)

    1989-01-01

    A radio frequency strain monitor includes a voltage controlled oscillator for generating an oscillating signal that is input into a propagation path. The propagation path is preferably bonded to the surface of a structure to be monitored and produces a propagated signal. A phase difference between the oscillating and propagated signals is detected and maintained at a substantially constant value which is preferably a multiple of 90.degree. by changing the frequency of the oscillating signal. Any change in frequency of the oscillating signal provides an indication of strain in the structure to which the propagation path is bonded.

  8. Supernova frequency estimates

    SciTech Connect

    Tsvetkov, D.Y.

    1983-01-01

    Estimates of the frequency of type I and II supernovae occurring in galaxies of different types are derived from observational material acquired by the supernova patrol of the Shternberg Astronomical Institute.

  9. 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.

  10. Frequency Hopping Transceiver Multiplexer

    DTIC Science & Technology

    1983-03-01

    8217 block number) frequency hopping, quadrature coupler, bandpass filter, coupling circuit, filter, helical resonator, matching network, PIN diode switch...which investigated the concept and feasibility of a 30MHz to 88MHz frequency hopping transceiver multiplexer. An approach which uses helical resonator...and Analysis 90 5.9.1 Helical Resonator 90 5.9.2 Shunt Capacitance Binary Bus Discussion 94 5.9.3 Resonator Design Decisions 97 5.9.4 Results and

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. Effective Frequency Technique

    NASA Technical Reports Server (NTRS)

    Kirk, C. Laurence; Weng, Chi Y.

    2002-01-01

    An effective monochromatic frequency technique is described to represent the effects of finite spectral bandwidth for active and passive measurements centered on an absorption line, a trough region, or a slowly varying spectral feature. For Gaussian and rectangular laser line shapes, the effective frequency is shown to have a simple form which depends only on the instrumental line shape and bandwidth and not on the absorption line profile. The technique yields accuracies better than 0.1% for bandwidths less than 0.2 times the atmospheric line width.

  16. 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.

  17. HIGHER FREQUENCY ULTRASONIC LIGHT MODULATORS.

    DTIC Science & Technology

    LIGHT ), (*MODULATORS, (*ULTRASONIC RADIATION, MODULATORS), OPTICAL COMMUNICATIONS, BANDWIDTH, TRANSDUCERS, HIGH FREQUENCY, VERY HIGH FREQUENCY, ATTENUATION, DATA PROCESSING, OPTICAL EQUIPMENT, ANALOG COMPUTERS, THEORY.

  18. Multiple Frequency Parametric Sonar

    DTIC Science & Technology

    2015-09-28

    300003 1 MULTIPLE FREQUENCY PARAMETRIC SONAR STATEMENT OF GOVERNMENT INTEREST [0001] The invention described herein may be manufactured and...beams. However, the multiple nonlinear interactions are not taken advantage of in order to generate additional efficiencies, bandwidth, and SNR...array. [0050] It will be understood that many additional changes in details, materials , steps, and arrangements of parts which have been described

  19. 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.

  20. 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.

  1. Multiband frequency selective surface

    NASA Astrophysics Data System (ADS)

    Wu, Te-Kao

    1998-10-01

    This paper addresses the similarity of microwave/millimeter wave frequency selective surfaces (FSS) to optical filters. Specifically, the design approaches of the 4-band FSSs developed for NASA's CASSINI high gain antenna are described in detail. Representative RF test results are given to demonstrate the validity of these designs. These design approaches are very general and can be applied to multiband optical filters.

  2. Spread Spectrum Frequency Management

    DTIC Science & Technology

    1989-06-01

    theoretically predicted behavior of the new system. Thp experimental program must include field tests in real propagation and interference environments...technological developments and without adequate overall knowledge of propagation characteristics or of other important uses that might require... propagation characteristics at the different frequency levels. The history of major spectrum allocations is then a 7 record of decisions primarily

  3. 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…

  4. Food frequency questionnaires.

    PubMed

    Pérez Rodrigo, Carmen; Aranceta, Javier; Salvador, Gemma; Varela-Moreiras, Gregorio

    2015-02-26

    Food Frequency Questionnaires are dietary assessment tools widely used in epidemiological studies investigating the relationship between dietary intake and disease or risk factors since the early '90s. The three main components of these questionnaires are the list of foods, frequency of consumption and the portion size consumed. The food list should reflect the food habits of the study population at the time the data is collected. The frequency of consumption may be asked by open ended questions or by presenting frequency categories. Qualitative Food Frequency Questionnaires do not ask about the consumed portions; semi-quantitative include standard portions and quantitative questionnaires ask respondents to estimate the portion size consumed either in household measures or grams. The latter implies a greater participant burden. Some versions include only close-ended questions in a standardized format, while others add an open section with questions about some specific food habits and practices and admit additions to the food list for foods and beverages consumed which are not included. The method can be self-administered, on paper or web-based, or interview administered either face-to-face or by telephone. Due to the standard format, especially closed-ended versions, and method of administration, FFQs are highly cost-effective thus encouraging its widespread use in large scale epidemiological cohort studies and also in other study designs. Coding and processing data collected is also less costly and requires less nutrition expertise compared to other dietary intake assessment methods. However, the main limitations are systematic errors and biases in estimates. Important efforts are being developed to improve the quality of the information. It has been recommended the use of FFQs with other methods thus enabling the adjustments required.

  5. Microwave Frequency Multiplier

    NASA Astrophysics Data System (ADS)

    Velazco, J. E.

    2017-02-01

    High-power microwave radiation is used in the Deep Space Network (DSN) and Goldstone Solar System Radar (GSSR) for uplink communications with spacecraft and for monitoring asteroids and space debris, respectively. Intense X-band (7.1 to 8.6 GHz) microwave signals are produced for these applications via klystron and traveling-wave microwave vacuum tubes. In order to achieve higher data rate communications with spacecraft, the DSN is planning to gradually furnish several of its deep space stations with uplink systems that employ Ka-band (34-GHz) radiation. Also, the next generation of planetary radar, such as Ka-Band Objects Observation and Monitoring (KaBOOM), is considering frequencies in the Ka-band range (34 to 36 GHz) in order to achieve higher target resolution. Current commercial Ka-band sources are limited to power levels that range from hundreds of watts up to a kilowatt and, at the high-power end, tend to suffer from poor reliability. In either case, there is a clear need for stable Ka-band sources that can produce kilowatts of power with high reliability. In this article, we present a new concept for high-power, high-frequency generation (including Ka-band) that we refer to as the microwave frequency multiplier (MFM). The MFM is a two-cavity vacuum tube concept where low-frequency (2 to 8 GHz) power is fed into the input cavity to modulate and accelerate an electron beam. In the second cavity, the modulated electron beam excites and amplifies high-power microwaves at a frequency that is a multiple integer of the input cavity's frequency. Frequency multiplication factors in the 4 to 10 range are being considered for the current application, although higher multiplication factors are feasible. This novel beam-wave interaction allows the MFM to produce high-power, high-frequency radiation with high efficiency. A key feature of the MFM is that it uses significantly larger cavities than its klystron counterparts, thus greatly reducing power density and arcing

  6. 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.

  7. Broadband frequency selective surface

    NASA Astrophysics Data System (ADS)

    Palma, D. A.; Wong, W. C.

    A method for designing broadband dichroic surfaces is described. A tripole and a Jerusalem cross are evaluated as candidate resonant elements. The effects of dielectric substrates on resonant frequency and bandwidth are investigated. The theoretical and measured frequency responses of tripoles and Jerusalem crosses are presented. It is observed that the metallic area of the tripole within a given period increases the bandwidth, the maximum theoretical bandwidth of the tripole dichroic sheet being about 50 percent; for a Jerusalem cross, increasing the metallic area of the two perpendicular strips and increasing the end cap capacitative loading increases the bandwidth to a theoretical maximum about 60 percent. Multilayered dichroic panels capable of producing a 4:1 stopband and 1.4:1 band separation have been designed for circular polarization and angles of incidence up to 40 degrees.

  8. 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.

  9. 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.

  10. [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.

  11. 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.

  12. [Frequency dependance of compliance].

    PubMed

    Gayrard, P

    1975-01-01

    Resistance of peripheral or "small" airways is only a small part of the total pulmonary resistance (Raw). Even considerable obstruction in these airways will have little effect on total resistance. Conversely this will lead to inequality in the time constants of units in parallel, and dynamic lung compliance (C dyn) shall fall as respiratory frequence increases. C dyn is measured from simultaneous recordings of transpulmonary pressure (esophageal balloon) and volume obtained from a volume displacement plethysmograph. If Raw and static compliance are found to be normal, the frequency dependance of compliance will result from peripheral airway obstruction only. Early stages of chronic airway obstruction can be established by this method. However this appear not suitable for wide-scale studies.

  13. Clustered frequency comb.

    PubMed

    Matsko, Andrey B; Savchenkov, Anatoliy A; Huang, Shu-Wei; Maleki, Lute

    2016-11-01

    We show theoretically that it is feasible to generate a spectrally broad Kerr frequency comb consisting of several spectral clusters phase matched due to interplay among second- and higher-order group velocity dispersion contributions. We validate the theoretical analysis experimentally by driving a magnesium fluoride resonator, characterized with 110 GHz free spectral range, with a continuous wave light at 1.55 μm and observing two comb clusters separated by nearly two-thirds of an octave.

  14. FET Frequency Discriminator.

    DTIC Science & Technology

    1982-03-01

    conversion . characteristic of the frequency discriminator is significant and :ending upon the specific system - may be the limiting factor in the accu of...the results obtained did not .-" allow for the accurate determinat ion of the change in impedance, addit ional 14 -~ 12V - - Figure 7. Impedance plot...44*. -. 7 ’I -- -..- ,. -, 4., /-.,’ .3 8 V ............... ... .. .$, L- 12v - Figure 9. Impedance plot tor five diodes inl parallel. A circuit was

  15. Cooled Ion Frequency Standard.

    DTIC Science & Technology

    2014-09-26

    report on our measurement of the Hg gj factor. This was an important step in the project because of the necessity of "mixing" the Zeeman 201Hg th 201...reported in Phys. Rev. Lett. in April, concentrates on detailed measurements made of systematic effects in this system. Two key features are: (1) an...stored ion frequency standard systematic effects since laser cooling is easier to achieve than in Hg . 2. "Strongly coupled" liquid and solid plasmas

  16. Low frequency cavitation erosion

    NASA Astrophysics Data System (ADS)

    Pardue, Sally J.; Chandekar, Gautam

    2002-11-01

    Damage of diesel engine piston sleeve liners due to cavitation of the coolant fluid can be severe. Coolant fluid additives are used to inhibit cavitation damage, and are evaluated by industry suppliers using ASTM G32-98 Standard Test Method for Cavitation Erosion Using Vibratory Apparatus. The ASTM G32-98 test procedure uses an ultrasonic horn at 20 kHz to vibrate a test button in the coolant. The test button mass loss and surface appearance are studied to sort the performance of new coolant additives. Mismatch between good lab performers and actual engine test runs has raised concerns over the current lab test. The frequency range of the current test has been targeted for investigation. A low frequency, less than 2000 Hz, test rig was built to explore the cavitation damage. The test system did produce cavitation on the surface of the test button for a period of 36 h, with minimal mass loss. The test rig experienced cyclic fatigue when test times were extended. The work is now focusing on designing a better test rig for long duration tests and on developing numerical models in order to explore the effects of cavitation excitation frequency on surface erosion.

  17. 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.

  18. 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

  19. Resonance frequency in ferromagnetic superlattices

    NASA Astrophysics Data System (ADS)

    Qiu, Rong-ke; Huang, An-dong; Li, Da; Zhang, Zhi-dong

    2011-10-01

    The resonance frequency in two-layer and three-layer ferromagnetic superlattices is studied, using the Callen's Green function method, the Tyablikov decoupling approximation and the Anderson-Callen decoupling approximation. The effects of interlayer exchange coupling, anisotropy, external magnetic field and temperature on the resonance frequency are investigated. It is found that the resonance frequencies increase with increasing external magnetic field. In a parameter region of the asymmetric system, each sublayer corresponds to its own resonance frequency. The anisotropy of a sublayer affects only the resonance frequency corresponding to this sublayer. The stronger the anisotropy, the higher is the resonance frequency. The interlayer exchange coupling affects only the resonance frequencies belonging to the sublayers connected by it. The stronger the interlayer exchange coupling, the higher are the resonance frequencies. All the resonance frequencies decrease as the reduced temperature increases. The results direct the method to enhance and adjust the resonance frequency of magnetic multilayered materials with a wide band.

  20. Arbitrary optical frequency synthesis traced to an optical frequency comb

    NASA Astrophysics Data System (ADS)

    Cai, Zihang; Zhang, Weipeng; Yang, Honglei; Li, Yan; Wei, Haoyun

    2016-11-01

    An arbitrary optical frequency synthesizer with a broad tuning range and high frequency accuracy is presented. The system includes an external cavity diode laser (ECDL) as the output laser, an Erbium-doped optical frequency comb being a frequency reference, and a control module. The optical frequency from the synthesizer can be continuously tuned by the large-scale trans-tooth switch and the fine intra-tooth adjustment. Robust feedback control by regulating the current and PZT voltage enables the ECDL to phase-lock to the Erbium-doped optical frequency comb, therefore to keep stable frequency output. In the meanwhile, the absolute frequency of the synthesizer is determined by the repetition rate, the offset frequency and the beat frequency. All the phase lock loops in the system are traced back to a Rubidium clock. A powerful and friendly software is developed to make the operation convenient by integrating the functions of frequency setting, tuning, tracing, locking and measuring into a LabVIEW interface. The output frequency tuning span and the uncertainty of the system are evaluated as >6 THz and <3 kHz, respectively. The arbitrary optical frequency synthesizer will be a versatile tool in diverse applications, such as synthetic wavelength based absolute distance measurement and frequency-stabilized Cavity Ring-Down Spectroscopy.

  1. 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.

  2. DEMODULATION OF FREQUENCY OR SPACE MODULATED LIGHT.

    DTIC Science & Technology

    LIGHT , DEMODULATION), (*OPTICAL COMMUNICATIONS, FREQUENCY MODULATION), (*FREQUENCY MODULATION, LIGHT ), OPTICAL TRACKING, BEAMS(ELECTROMAGNETIC), DEFLECTION, MICROWAVE FREQUENCY, ELECTRON BEAMS, PHOTOCATHODES

  3. 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.

  4. 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.

  5. 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)

  6. High frequency pulsed electromigration

    NASA Astrophysics Data System (ADS)

    Malone, David Wayne

    Electromigration life tests were performed on copper-alloyed aluminum test structures that were representative of modern CMOS metallization schemes, complete with Ti/TiN cladding layers and a tungsten-plug contact at the cathode. A total of 18 electrical stress treatments were applied. One was a DC current of 15 mA. The other 17 were pulsed currents, varied according to duty cycle and frequency. The pulse amplitude was 15 mA (˜2.7 × 10sp6 A/cmsp2) for all treatments. Duty cycles ranged from 33.3% to 80%, and frequencies fell into three rough ranges-100 KHz, 1 MHz, and 100 MHz. The ambient test temperature was 200sp°C in all experiments. Six to 9 samples were subjected to each treatment. Experimental data were gathered in the form of test stripe resistance versus time, R(t). For purposes of lifetime analysis, "failure" was defined by the criterion R(t)/R(0) = 1.10, and the median time to failure, tsb{50}, was used as the primary basis of comparison between test groups. It was found that the dependence of tsb{50} on pulse duty cycle conformed rather well to the so-called "average current density model" for duty cycles of 50% and higher. Lifetimes were less enhanced for a duty cycle of 33.3%, but they were still considerably longer than an "on-time" model would predict. No specific dependence of tsb{50} on pulse frequency was revealed by the data, that is, reasonably good predictions of tsb{50} could be made by recognizing the dominant influence of duty cycle. These findings confirm that IC miniaturization can be more aggressively pursued than an on-time prediction would allow. It is significant that this was found to be true for frequencies on the order of 100 MHz, where many present day digital applications operate. Post-test optical micrographs were obtained for each test subject in order to determine the location of electromigration damage. The pulse duty cycle was found to influence the location. Most damage occurred at the cathode contact, regardless of

  7. Frequency Domain Identification Toolbox

    NASA Technical Reports Server (NTRS)

    Horta, Lucas G.; Juang, Jer-Nan; Chen, Chung-Wen

    1996-01-01

    This report documents software written in MATLAB programming language for performing identification of systems from frequency response functions. MATLAB is a commercial software environment which allows easy manipulation of data matrices and provides other intrinsic matrix functions capabilities. Algorithms programmed in this collection of subroutines have been documented elsewhere but all references are provided in this document. A main feature of this software is the use of matrix fraction descriptions and system realization theory to identify state space models directly from test data. All subroutines have templates for the user to use as guidelines.

  8. 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.

  9. Frequency Assignment Subcommittee (FAS)

    DTIC Science & Technology

    2010-03-01

    4 • 4 GHz • 14 – 15 GHz • 7/8 GHz when IRAC approved 4 Frequency Application P ( t)rocess con  C l ith Ch l Pl C tomp y w anne ans on • Military...EXD • Change 141 date • Submit Renewals at least 60 days prior to expiration date  Can’t serial replace FRRS only record 6  IRAC docs listed...in NTIA Manual • One site, Poseidon Park, approved at IRAC but not signed by Chair – awaiting outcome of change to 7.11 paper b itt d b FASsu m e y

  10. Impacts of frequency increment errors on frequency diverse array beampattern

    NASA Astrophysics Data System (ADS)

    Gao, Kuandong; Chen, Hui; Shao, Huaizong; Cai, Jingye; Wang, Wen-Qin

    2015-12-01

    Different from conventional phased array, which provides only angle-dependent beampattern, frequency diverse array (FDA) employs a small frequency increment across the antenna elements and thus results in a range angle-dependent beampattern. However, due to imperfect electronic devices, it is difficult to ensure accurate frequency increments, and consequently, the array performance will be degraded by unavoidable frequency increment errors. In this paper, we investigate the impacts of frequency increment errors on FDA beampattern. We derive the beampattern errors caused by deterministic frequency increment errors. For stochastic frequency increment errors, the corresponding upper and lower bounds of FDA beampattern error are derived. They are verified by numerical results. Furthermore, the statistical characteristics of FDA beampattern with random frequency increment errors, which obey Gaussian distribution and uniform distribution, are also investigated.

  11. 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

  12. 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)

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. High frequency nanotube oscillator

    DOEpatents

    Peng, Haibing [Houston, TX; Zettl, Alexander K [Kensington, TX

    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.

  20. 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.

  1. Frequencies of restriction sites.

    PubMed Central

    Waterman, M S

    1983-01-01

    Restriction sites or other sequence patterns are usually assumed to occur according to a Poisson distribution with mean equal to the reciprocal of the probability of the given site or pattern. For situations where non-overlapping occurrences of patterns, such as restriction sites, are the objects of interest, this note shows that the Poisson assumption is frequently misleading. Both the case of base composition (independent bases) and of dinucleotide frequencies (Markov chains) are treated. Moreover, a new technique is presented which allows treatment of collections of patterns, where the departure from the Poisson assumption is even more striking. This later case includes double digests, and an example of a five enzyme digest is included. PMID:6324109

  2. High-frequency broadband transformers

    NASA Astrophysics Data System (ADS)

    London, S. E.; Tomashevich, S. V.

    1981-05-01

    A systematic review of the theory and design principles of high-frequency broadband transformers is presented. It is shown that the transformers of highest performance are those whose coils consist of strips of double-wire and multiwire transmission lines. Such devices are characterized by a wide operating frequency range, and make possible operation at microwave frequencies at high levels of transmitted power.

  3. 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.

  4. 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.

  5. Mass spectrometry of diffuse coplanar surface barrier discharge: influence of discharge frequency and oxygen content in N2/O2 mixture*

    NASA Astrophysics Data System (ADS)

    Čech, Jan; Brablec, Antonín; Černák, Mirko; Puač, Nevena; Selaković, Nenad; Petrović, Zoran Lj.

    2017-02-01

    Diffuse Coplanar Surface Barrier Discharge (DCSBD) has been studied extensively for industrial applications in recent decade. So far, limited information was available on the production of ozone or nitrogen oxides important for industrial deployment of DCSBD. In this paper results of mass spectrometry of DCSBD performed at atmospheric pressure are presented. DCSBD mass spectra were studied for different oxygen contents in N2/O2 working gas mixture at low flow rate (estimated residence time in discharge chamber was approx. 3 s). Influence of the driving frequency (15, 30 and 50 kHz) at constant high voltage amplitude was studied as well. Ozone and NO production in DCSBD are given as typical representatives. Production of ozone decreases with the driving frequency, which could be attributed to the gas heating at higher frequencies.

  6. Towards VECSEL frequency combs

    NASA Astrophysics Data System (ADS)

    Wilcox, Keith G.

    2013-02-01

    Significant progress has been made over the last year towards generating frequency combs using VECSELs. Here, I will discuss recent progress made generating < 4kW peak power femtosecond pulse VECSELs, where we have achieved 3.3 W average power with 400 fs pulse duration at 1.7 GHz repetition rate. This has been achieved by exploiting the rapid power scaling progress made in the field of CW VECSELs [1]. The gain structure used here is grown and processed by the University of Marburg, and the window layer is etched for anti-resonance to increase the gain bandwidth and reduce the dispersion [2]. We have used this to generate supercontinuum, achieving 45 % throughput in a 2.2 micron core photonic crystal fiber when the VECSEL produced 1 W average output power. A continuum with a width of 175 nm is generated. At higher average powers heating of the fiber tip reduces coupling efficiency which limits the supercontinuum bandwidth and we will discuss measures to avoid this. Finally, I will outline approaches to further reduce the pulse length, whilst maintaining the average power, to a point where generating coherent octave spanning supercontinuum, suitable for F-2F stabilization should become a reality.

  7. 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.

  8. Multifractal Flood Frequency Analysis

    NASA Astrophysics Data System (ADS)

    Tchiguirinskaia, I.; Schertzer, D.; Lovejoy, S.

    2007-12-01

    Hydrology and more generally sciences involved in water resources management, researches and technological or operational development face a fundamental difficulty: the extreme variability of hydrological fields. It clearly appears today that this variability is a function of the observation scale and yield natural hazards such as floods or droughts. The estimation of return periods for extreme precipitation and flooding events requires a model of the natural (unperturbed) statistical behaviour of the probability tails and the possible clustering (including possible long-range dependencies) of the extremes. Appropriate approaches for handling such non classical variability over wide ranges of time and space scale do exist. They are based on a fundamental property of the non-linear equations: scale invariance. Its specific framework is that of multifractals. In this framework hydrological variability builds up scale by scale leading to non-classical statistics; this provides the key element needed to better understand and predict floods. Scaling is a verifiable physical principle which can be exploited to model hydrological processes and estimate their statistics over wide ranges of space-time scales. We first present the Multifractal Flood Frequency Analysis (MFFA) tool and illustrate some results of its application to a large database (for more than 16000 selected stations over USA and Canada). We then discuss its efficiency by showing how the mean flow information - coupled with universal multifractal parametrizations with power law tails - can be used to estimate return times for extreme flood events.

  9. 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

    2015-08-11

    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.

  10. 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

  11. Development of frequency synthesizer for fast frequency hopping communication equipment

    NASA Astrophysics Data System (ADS)

    Sekizawa, Shinya; Moriyama, Eimatsu

    1990-06-01

    A frequency synthesizer with rapid operation is necessary for the development of fast frequency hopping communication systems in land mobile radios. On the other hand, accuracy is not so important in the fast frequency hopping systems when envelope detection is employed in a receiver. Currently, there are several types of frequency synthesizers. However, they are not sufficient in terms of switching speed, size and cost. A frequency synthesizer with rapid hopping based on a new operating principle is proposed and developed. It is a small synthesizer, consisting of digital devices, available at a low cost. The experimental results show that the synthesizer has the switching performance necessary for frequency hopping land mobile radios. This paper describes the operating principle and the experimental results of the proposed synthesizer.

  12. 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.

  13. Magic Frequencies for Cesium Primary-Frequency Standard

    NASA Astrophysics Data System (ADS)

    Flambaum, V. V.; Dzuba, V. A.; Derevianko, A.

    2008-11-01

    We consider microwave hyperfine transitions in the ground state of cesium and rubidium atoms which are presently used as the primary and the secondary frequency standards. The atoms are confined in an optical lattice generated by a circularly polarized laser field. We demonstrate that applying an external magnetic field with appropriately chosen direction may cancel dynamic Stark frequency shift making the frequency of the clock transition insensitive to the strengths of both the laser and the magnetic fields. This can be attained for practically any laser frequency which is sufficiently distant from a resonance.

  14. Magic Frequencies for Cesium Primary-Frequency Standard

    SciTech Connect

    Flambaum, V. V.; Dzuba, V. A.; Derevianko, A.

    2008-11-28

    We consider microwave hyperfine transitions in the ground state of cesium and rubidium atoms which are presently used as the primary and the secondary frequency standards. The atoms are confined in an optical lattice generated by a circularly polarized laser field. We demonstrate that applying an external magnetic field with appropriately chosen direction may cancel dynamic Stark frequency shift making the frequency of the clock transition insensitive to the strengths of both the laser and the magnetic fields. This can be attained for practically any laser frequency which is sufficiently distant from a resonance.

  15. Digital frequency control of satellite frequency standards. [Defense Navigation Satellites

    NASA Technical Reports Server (NTRS)

    Nichols, S. A.

    1973-01-01

    In the Frequency and Time Standard Development Program of the TIMATION System, a new miniaturized rubidium vapor frequency standard has been tested and analyzed for possible use on the TIMATION 3A launch, as part of the Defense Navigation Satellite Development Program. The design and construction of a digital frequency control was required to remotely control this rubidium vapor frequency standard as well as the quartz oscillator in current use. This control must be capable of accepting commands from a satellite telemetry system, verify that the correct commands have been sent and control the frequency to the requirements of the system. Several modifications must be performed to the rubidium vapor frequency standard to allow it to be compatible with the digital frequency control. These include the addition of a varactor to voltage tune the coarse range of the flywheel oscillator, and a modification to supply the C field current externally. The digital frequency control for the rubidium vapor frequency standard has been successfully tested in prototype form.

  16. 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

  17. 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.

  18. 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.

  19. Effective switching frequency multiplier inverter

    DOEpatents

    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.

  20. 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.

  1. Binaural beats at high frequencies.

    PubMed

    McFadden, D; Pasanen, E G

    1975-10-24

    Binaural beats have long been believed to be audible only at low frequencies, but an interaction reminiscent of a binaural beat can sometimes be heard when different two-tone complexes of high frequency are presented to the two ears. The primary requirement is that the frequency separation in the complex at one ear be slightly different from that in the other--that is, that there be a small interaural difference in the envelope periodicities. This finding is in accord with other recent demonstrations that the auditory system is not deaf to interaural time differences at high frequencies.

  2. Frequency hopping millimeter wave reflectometer

    NASA Astrophysics Data System (ADS)

    Cupido, L.; Sánchez, J.; Estrada, T.

    2004-10-01

    Reflectometry techniques are employed to study density fluctuations in fusion plasmas either using one channel or two channels with slightly different frequencies, to probe simultaneously closely spaced plasma layers (for radial correlation studies). The present article describes a novel system with increasing measuring capability utilizing only one single frequency that can be hopped during the discharge. This broadband fast hopping mm-wave reflectometer (BFHR) has been developed for both ASDEX upgrade (Max Plank Institute-Garching-Germany) and TJ-II stellarator (CIEMAT-Spain). The BFHR incorporates frequency synthesizers at microwave frequencies multiplied into the millimeter-wave range and uses heterodyne detection for sensitive phase and amplitude measurements.

  3. 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.

  4. 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.

  5. Frequency dependent polarization analysis of high-frequency seismograms

    NASA Astrophysics Data System (ADS)

    Park, Jeffrey; Vernon, Frank L., III; Lindberg, Craig R.

    1987-11-01

    We present a multitaper algorithm to estimate the polarization of particle motion as a function of frequency from three-component seismic data. This algorithm is based on a singular value decomposition of a matrix of eigenspectra at a given frequency. The right complex eigenvector zˆ corresonding to the largest singular value of the matrix has the same direction as the dominant polarization of seismic motion at that frequency. The elements of the polarization vector zˆ specify the relative amplitudes and phases of motion measured along the recorded components within a chosen frequency band. The width of this frequency band is determined by the time-bandwidth product of the prolate spheroidal tapers used in the analysis. We manipulate the components of zˆ to determine the apparent azimuth and angle of incidence of seismic motion as a function of frequency. The orthogonality of the eigentapers allows one to calculate easily uncertainties in the estimated azimuth and angle of incidence. We apply this algorithm to data from the Anza Seismic Telemetered Array in the frequency band 0 ≤ ƒ ≤ 30 Hz. The polarization is not always a smooth function of frequency and can exhibit sharp jumps, suggesting the existence of scattered modes within the crustal waveguide and/or receiver site resonances.

  6. a Radio-Frequency

    NASA Astrophysics Data System (ADS)

    Foo, Thomas Kwok-Fah

    Radio-frequency (RF) inhomogeneity encountered in magnetic resonance (MR) imaging poses a significant impediment to obtaining images of the highest diagnostic quality. This inhomogeneity arises from the conductivity effect, which attenuates the RF field with increasing depth, and the permittivity effect. The latter is the dominant effect at 1.5 Tesla (64 MHz), and contributes to standing waves within the body. A theoretical model has been developed which describes these effects for an infinitely long right circularly cylindrical object inside a concentric RF coil and RF shield. This model assumes that the RF field propagates as a travelling wave in the z direction, along the long axis of the cylinder. The resulting solutions adequately predict the field distribution for RF coils which have both a finite wavelength and an infinite wavelength in z. This corresponds to high-pass and low-pass birdcage resonators, respectively, that are in general used in MR imaging. Standing wave models are easily obtained from the superposition of solutions of two travelling waves in opposite directions. The results of this model indicate that the axial propagation constant k_{z} is a strong function of the dielectric present in the coil -to-shield space. The field distribution in the axial plane can be represented by the Bessel function J_1(k _{rho}r), where k _sp{rho}{2} = k^2-k_sp{z}{2} . By varying the dielectric material occupying the coil-to-shield space, an optimum value of k _{z} can be obtained for a particular coil and shield configuration which minimizes the amplitude variations in the axial plane. Experimental verification of the theoretical model has been obtained. These measurements were performed on a non-resonant, travelling wave test coil with a saline phantom as a load simulating the body. The measured field profiles in the axial plane agree with the predicted values, establishing the validity of the theoretical model. As expected, optimal RF homogeneity was obtained

  7. Frequency conversion of structured light.

    PubMed

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

    2016-02-15

    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.

  8. 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.

  9. 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…

  10. 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

  11. Low-Frequency Navigational System

    NASA Technical Reports Server (NTRS)

    Wallis, D. E.

    1985-01-01

    Accurate vehicle position determination over 50 by 50-km service area accomplished by low-frequency-radio navigational system comprised of four frequency/phase comparison transmitters and receivers. Use of grid-calibration table permits accurate position determination in vehicle receiver system.

  12. 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.…

  13. Negative-Frequency Resonant Radiation

    NASA Astrophysics Data System (ADS)

    Rubino, E.; McLenaghan, J.; Kehr, S. C.; Belgiorno, F.; Townsend, D.; Rohr, S.; Kuklewicz, C. E.; Leonhardt, U.; König, F.; Faccio, D.

    2012-06-01

    Optical solitons or solitonlike states shed light to blueshifted frequencies through a resonant emission process. We predict a mechanism by which a second propagating mode is generated. This mode, called negative resonant radiation, originates from the coupling of the soliton mode to the negative-frequency branch of the dispersion relation. Measurements in both bulk media and photonic-crystal fibers confirm our predictions.

  14. 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.

  15. Frequency-controlled voltage regulator

    NASA Technical Reports Server (NTRS)

    Mclyman, W. T.

    1980-01-01

    Converting input ac to higher frequency reduce size and weight and makes possible unique kind of regulation. Since conversion frequency is above range of human hearing, supply generated on audible noise. It also exploits highfrequency conversion features to regulate its output voltage in novel way. Circuit is inherently short-circuit proof.

  16. 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…

  17. Frequency fluctuations in silicon nanoresonators

    PubMed Central

    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

    2016-01-01

    Frequency stability is key to 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 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

  18. 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.

  19. The Low Frequency Space Array

    NASA Technical Reports Server (NTRS)

    Dennison, Brian; Weiler, K. W.; Johnston, K. J.; Simon, R. S.; Spencer, J. H.; Hammarstrom, L. M.; Wilhelm, P. G.; Kaiser, M. L.; Desch, M. D.; Fainberg, J.

    1987-01-01

    The Low Frequency Space Array (LFSA) is a conceptual mission to survey the entire sky and to image individual sources at frequencies between 1.5 and 26 MHz, a frequency range over which the earth's ionosphere transmits poorly or not at all. With high resolution, high sensitivity observations, a new window will be opened in the electromagnetic spectrum for astronomical investigation. Also, extending observations down to such low frequencies will bring astronomy to the fundamental limit below which the galaxy becomes optically thick due to free-free absorption. A number of major scientific goals can be pursued with such a mission, including mapping galactic emission and absorption, studies of individual source spectra in a frequency range where a number of important processes may play a role, high resolution imaging of extended sources, localization of the impulsive emission from Jupiter, and a search for coherent emission processes.

  20. 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.

  1. Monolithically integrated absolute frequency comb laser system

    SciTech Connect

    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.

  2. 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.

  3. 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.

  4. Coexistence under positive frequency dependence.

    PubMed Central

    Molofsky, J.; Bever, J. D.; Antonovics, J.

    2001-01-01

    Negative frequency dependence resulting from interspecific interactions is considered a driving force in allowing the coexistence of competitors. While interactions between species and genotypes can also result in positive frequency dependence, positive frequency dependence has usually been credited with hastening the extinction of rare types and is not thought to contribute to coexistence. In the present paper, we develop a stochastic cellular automata model that allows us to vary the scale of frequency dependence and the scale of dispersal. The results of this model indicate that positive frequency dependence will allow the coexistence of two species at a greater rate than would be expected from chance. This coexistence arises from the generation of banding patterns that will be stable over long time-periods. As a result, we found that positive frequency-dependent interactions over local spatial scales promote coexistence over neutral interactions. This result was robust to variation in boundary conditions within the simulation and to variation in levels of disturbance. Under all conditions, coexistence is enhanced as the strength of positive frequency-dependent interactions is increased. PMID:11217898

  5. Frequency dependence of organic magnetoresistance

    NASA Astrophysics Data System (ADS)

    Wang, Fujian; Rybicki, James; Lin, Ran; Hutchinson, Kent; Hou, Jia; Wohlgenannt, Markus

    2011-03-01

    Organic magnetoresistive (OMAR) devices show a large enough magnetoresistive response (typically 10%) for potential applications as magnetic field sensors. However, applications often require sensing high frequency magnetic fields, and the examination of the frequency-dependent magnetoresistive response is therefore required. Analysis of time constants that limit the frequency response may also shed light on the mechanism behind the OMAR effect, because different OMAR mechanisms occur at different time scales In our experiments, the AC magnetic field is supplied by a coil with a ferrite core which is driven by a function generator The AC magnet shows a frequency response that is almost flat up to 1MHz. We found that the OMAR frequency limit is about 10 kHz for a typical organic semiconductor device and at least 100 kHz for devices made from a doped polymer film. We also performed capacitance and conductance vs. frequency measurements to understand the origin of the observed limit frequencies. This work was supported by Army MURI under GrantNo. W911NF-08-1-0317 and NSF under Grant No. ECS 0725280.

  6. Frequency retrace of quartz oscillators

    NASA Astrophysics Data System (ADS)

    Euler, F.; Yannoni, N. F.

    Frequency retrace measurements are reported on oven controlled quartz oscillators utilizing AT and SC cut plated and BVA resonators. Prior to full aging, the retrace error is added to the aging effect. With well-aged resonators, after one or several on-off cycles, the frequency settles at a new level characteristic for intermittent operation. Severe frequency shifts have sometimes been found after the first restart following prolonged continuous operation. SC cut resonators appear to show distinctly smaller retrace errors than AT cut.

  7. Frequency dependence of organic magnetoresistance

    NASA Astrophysics Data System (ADS)

    Wagemans, W.; Janssen, P.; van der Heijden, E. H. M.; Kemerink, M.; Koopmans, B.

    2010-09-01

    To identify the microscopic mechanisms of organic magnetoresistance (OMAR), the dependency on the frequency of the applied magnetic field is explored, which consists of a dc and ac component. The measured magnetoconductance decreases when the frequency is increased. The decrease is stronger for lower voltages, which is shown to be linked to the presence of a negative capacitance, as measured with admittance spectroscopy. The negative capacitance disappears when the frequency becomes comparable to the inverse transit time of the minority carriers. These results are in agreement with recent interpretations that magnetic field effects on minority carrier mobility dominate OMAR.

  8. Estimations of uncertainties of frequencies

    NASA Astrophysics Data System (ADS)

    Eyer, Laurent; Nicoletti, Jean-Marc; Morgenthaler, Stephan

    2016-10-01

    Diverse variable phenomena in the Universe are periodic. Astonishingly many of the periodic signals present in stars have timescales coinciding with human ones (from minutes to years). The periods of signals often have to be deduced from time series which are irregularly sampled and sparse, furthermore correlations between the brightness measurements and their estimated uncertainties are common. The uncertainty on the frequency estimation is reviewed. We explore the astronomical and statistical literature, in both cases of regular and irregular samplings. The frequency uncertainty is depending on signal to noise ratio, the frequency, the observational timespan. The shape of the light curve should also intervene, since sharp features such as exoplanet transits, stellar eclipses, raising branches of pulsation stars give stringent constraints. We propose several procedures (parametric and nonparametric) to estimate the uncertainty on the frequency which are subsequently tested against simulated data to assess their performances.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Colloidal Metamaterials at Optical Frequencies

    DTIC Science & Technology

    2014-07-18

    AFRL-OSR-VA-TR-2014-0184 Colloidal Metamaterials at Optical Frequencies Jennifer Dionne LELAND STANFORD JUNIOR UNIV CA Final Report 07/18/2014...Prescribed by ANSI Std. Z39.18 Colloidal Metamaterials at Optical Frequencies Annual Report, June 30, 2014 A. Investigators PI: Jennifer Dionne...team has combined theoretical and experimental methods to produce a colloidally -synthesized metamaterial fluid, or “metafluid,” exhibiting strong

  15. 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.

  16. Low frequency split cycle cryocooler

    NASA Technical Reports Server (NTRS)

    Bian, S. X.; Zhang, Y. D.; Wan, W. W.; Wang, L.; Hu, Q. C.

    1985-01-01

    A split cycle Stirling cryocooler with two different drive motors and operating at a low drive frequency can have high thermodynamic efficiency. The temperature of the cold end of the cryocooler varies with drive frequency, voltage of the input electrical power and initial charge pressure values. The cryocooler operating at 8 Hz can provide 7 watts of refrigeration at 77 K for 230 watts of electrical input power.

  17. 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.

  18. An isothermal flowmeter with improved frequency response for measuring tissue blood flow.

    PubMed

    Olshausen, K; Gross, R; Kirchheim, H

    1976-11-30

    An isothermal flowmeter with improved frequency response for measuring tissue blood flow was developed using thermistors. Direct heating of the thermistors allows a simple construction of small (0.5 mm outer diameter) capillary probes which do not require any additional heating coil. The changes of a feedback current necessary to keep the thermistor at a constant increment above tissue temperature indicate tissue blood flow; a second thermistor compensates variations of tissue temperature. The dynamic performance of the device shows a low-pass characteristic with a cut-off frequency higher than 5 Hz. For low flow rates the output signal was found to be proportional to the flow; for higher flow rates a linearization was necessary. Since tissue temperature can be recorded continuously, intermittent quantitative in-vivo calibration seems possibly by evaluation of "heater off" curves in the perfused and non-perfused tissue. As the flowmeter is insensitive to tissue temperature, it can be used for long-term recordings.

  19. 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…

  20. The measurement of frequency and frequency stability of precision oscillators

    NASA Technical Reports Server (NTRS)

    Allan, D. W.

    1974-01-01

    The specification and performance of precision oscillators is discussed as a very important topic to the owners and users of these oscillators. This paper presents at the tutorial level some convenient methods of measuring the frequencies of precision oscillators -- giving advantages and disadvantages of these methods. Further it is shown that by processing the data from the frequency measurements in certain ways, one may be able to state more general characteristics of the oscillators being measured. The goal in this regard is to allow the comparisons of different manufacturers' specifications and more importantly to help assess whether these oscillators will meet the standard of performance the user may have in a particular application.

  1. 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...

  2. 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...

  3. 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...

  4. 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...

  5. 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...

  6. 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...

  7. 47 CFR 87.173 - Frequencies.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Frequencies. 87.173 Section 87.173... Frequencies § 87.173 Frequencies. (a) The table in paragraph (b) of this section lists assignable carrier frequencies or frequency bands. (1) The single letter symbol appearing in the “Subpart” column indicates...

  8. 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...

  9. 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...

  10. 47 CFR 80.1077 - Frequencies.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Frequencies. 80.1077 Section 80.1077... Frequencies. The following table describes the frequencies used in the Global Maritime Distress and Safety... frequency 9 GHz radar transponders 9200-9500 MHz. 1 Frequency 156.525 MHz can be used for...

  11. 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...

  12. 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...

  13. 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...

  14. 47 CFR 80.1077 - Frequencies.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Frequencies. 80.1077 Section 80.1077... Frequencies. The following table describes the frequencies used in the Global Maritime Distress and Safety... frequency 9 GHz radar transponders 9200-9500 MHz. 1 Frequency 156.525 MHz can be used for...

  15. 47 CFR 87.173 - Frequencies.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Frequencies. 87.173 Section 87.173... Frequencies § 87.173 Frequencies. (a) The table in paragraph (b) of this section lists assignable carrier frequencies or frequency bands. (1) The single letter symbol appearing in the “Subpart” column indicates...

  16. 47 CFR 87.173 - Frequencies.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Frequencies. 87.173 Section 87.173... Frequencies § 87.173 Frequencies. (a) The table in paragraph (b) of this section lists assignable carrier frequencies or frequency bands. (1) The single letter symbol appearing in the “Subpart” column indicates...

  17. 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.

  18. Digital frequency tracking filter design

    NASA Astrophysics Data System (ADS)

    Yeh, Hen-Geul

    In this paper, three design approaches of the digital frequency tracking filter are presented. The common structure of these approaches are: (1) to have a bank of filters to process the received signals (signals are separated into a few sections as the excitation frequency sweeps from low to high) from the test specimen, (2) to use the Welsh method to compute the spectral density via the FFT (Fast Fourier Transform) algorithm. The bandpass filter bank is employed in the 1st approach to remove the noise which is contained in all sections of received signals. The decimation and interpolation schemes are used in the 2nd approach to reduce the unnecessary computations which exist in the over sampled sections of received signals. The modulation and demodulation schemes (for high-frequency sections only) combined with decimation and interpolation schemes (for over sampled section only) are employed in the 3rd approach. The modulation and demodulation schemes are used to shift the spectrum from high-frequency to low-frequency for simplying the filtering process via LPFs (Low Pass Filters).

  19. 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.

  20. 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.

  1. 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.

  2. Low-frequency electrical properties.

    USGS Publications Warehouse

    Olhoeft, G.R.

    1985-01-01

    In the interpretation of induced polarization data, it is commonly assumed that metallic mineral polarization dominantly or solely causes the observed response. However, at low frequencies, there is a variety of active chemical processes which involve the movement or transfer of electrical charge. Measurements of electrical properties at low frequencies (such as induced polarization) observe such movement of charge and thus monitor many geochemical processes at a distance. Examples in which this has been done include oxidation-reduction of metallic minerals such as sulfides, cation exchange on clays, and a variety of clay-organic reactions relevant to problems in toxic waste disposal and petroleum exploration. By using both the frequency dependence and nonlinear character of the complex resistivity spectrum, these reactions may be distinguished from each other and from barren or reactionless materials.-Author

  3. 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).

  4. Variable frequency microwave heating apparatus

    SciTech Connect

    Bible, D.W.; Lauf, R.J.; Johnson, A.C.; Thigpen, L.T.

    1999-10-05

    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).

  5. 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.

  6. Molecular Spectroscopy with Frequency Combs

    NASA Astrophysics Data System (ADS)

    Coddington, Ian

    2010-03-01

    Pulsed femtosecond frequency combs are rapidly developing as a powerful spectroscopic tool. As a spectroscopic source stabilized frequency combs potentially offer broad spectral coverage, near perfect frequency accuracy, low timing jitter and broadband compatibility with resonant cavities. This talk will focus on the first three advantages in a dual comb spectroscopic technique that is highly analogous to traditional Fourier transform spectroscopy. In the dual comb approach, (pioneered in the THz by Keilmann, Van der Weide and coworkers under the name multi-heterodyne spectroscopy), one comb is used to sample a gas and a second frequency comb serves as a local oscillator (LO) that samples the first comb. The LO is held at a slightly different repetition rate than the first comb. When viewed in the time domain, the comb sources each emit a train of pulses. With the difference in repetition rates, for each successive pair of pulses, the timing between the sample and LO laser pulses shifts slightly. Through successive measurements, the LO pulses read out the entire time domain structure of the transmitted sample pulse. Through a Fourier transform, we recover the broadband, complex, absorption profile of the sample gas. In analogy to a Fourier transform spectrometer the LO serves as a scanning interferometer arm. The removal of moving parts from the system along with the addition of high brightness collimated sources brings new flexibility to FTIR spectroscopy. This talk will focus on strengths and limitations of the dual comb technique. Specifically we focus on comb stabilization techniques that allow for long averaging periods, firmware based averaging techniques that keep data sizes manageable and allow for realtime data processing, time domain multiplexing of signal and reference data for continuous removal of system drift, and difference frequency generation techniques to extend this system into the mid IR. We will also discuss methods to improve the sensitivity

  7. 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.

  8. 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.

  9. 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…

  10. 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.

  11. Variable frequency microwave moisture leveling

    SciTech Connect

    Hamann, M.R.

    1999-07-01

    A variable frequency microwave system was examined to replace an existing carousel resistance heating line as the method for drying of mouth swabs for the pharmaceutical industry. A pharmaceutical manufacturer located in Northern Illinois had a resistive heating system that was not drying product satisfactorily, thus requiring additional ambient drying time even after a 30-minute drying cycle. Since the swabs are used for the healthcare industry, the amount of moisture present after drying was critical to avoid the formation of mold on the product that could have lead to dissatisfied customers. Variable frequency microwave moisture leveling allowed better product quality while turning the manufacturing operation into just in time delivery. During pilot scale testing, a 300 times cycle improvement was realized for variable frequency microwave compared to the conventional carousel resistive drying unit (24 hours to 5 minutes). The projected total cost of the variable frequency microwave system is $1 million, with 25% of the cost in the microwave unit and 70% of the cost in a new autobagging system. The author projected a $0.58 million saving per year in reduced operational costs with productivity increases. Although the project would have had a 1.8 year payback time, it was not implemented due to the capital expense and risk of an unknown technology.

  12. 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)

  13. 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.

  14. 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.

  15. The vibrational frequencies of difluoroethyne

    NASA Technical Reports Server (NTRS)

    Breidung, Juergen; Schneider, Winfried; Thiel, Walter; Lee, Timothy J.

    1992-01-01

    Ab initio coupled-cluster calculations with single and double excitations and with a perturbational treatment of connected triple excitations are reported for difluoroethyne using large basis sets. The results for the transbending mode nu-4 are extremely sensitive to electron correlation and basis set effects. The best theoretical and experimental estimates for the fundamental vibrational frequencies are in excellent agreement.

  16. 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

  17. Frequency discrimination of brief tonal steps as a function of frequency in the lesser bulldog bat.

    PubMed

    Roverud, R C

    1999-09-01

    In a two-alternative, forced-choice task lesser bulldog bats were trained to distinguish between a pure tone pulse and a pulse composed of a series of brief tonal steps oscillating between two different frequencies. The tone-step pulse gradually approximates the pure tone pulse as the frequency difference between the steps becomes progressively smaller. Frequency difference limens for the brief tonal frequency steps were determined for a broad range of ultrasonic frequencies. The variation in tone-step difference limens with frequency appears to be correlated to the frequency structure of the bat's short-constant-frequency/frequency-modulated echolocation sound. There was a marked decline in the value of the relative frequency difference limens (Weber ratio) over a fairly narrow range of frequencies above the constant frequency and a sharp increase in threshold above this range. The relative thresholds for frequency discrimination were small and uniform over the frequency range of the frequency-modulated sweep and increased for frequencies below the frequency-modulated sweep. Thus, the most accurate frequency-discrimination abilities occur over a narrow frequency range around the frequency of the constant-frequency component of returning echoes. Frequency discrimination over the range of frequencies of the frequency-modulated component is relatively good.

  18. GPS Block IIF Atomic Frequency Standard Analysis

    DTIC Science & Technology

    2010-11-01

    Frequency stability of GPS constellation for October 2010 (NGA products). REFERENCES [1] “ Rubidium Atomic Frequency Standard (RAFS) GPS...Block IIR Rubidium Atomic Frequency Standard Life Test,” in Proceedings of the 30 th Annual Precise Time and Time Interval (PTTI) Applications and...42 nd Annual Precise Time and Time Interval (PTTI) Meeting 181 GPS BLOCK IIF ATOMIC FREQUENCY STANDARD ANALYSIS

  19. 47 CFR 95.1401 - Frequency.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... SERVICES Personal Locator Beacons (PLB). § 95.1401 Frequency. The frequency band 406.0-406.1 MHz is an emergency and distress frequency band available for use by Personal Locator Beacons (PLBs). Personal Locator Beacons that transmit on the frequency band 406.0-406.1 MHz must use G1D emission. Use of...

  20. 47 CFR 95.1401 - Frequency.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... SERVICES Personal Locator Beacons (PLB). § 95.1401 Frequency. The frequency band 406.0-406.1 MHz is an emergency and distress frequency band available for use by Personal Locator Beacons (PLBs). Personal Locator Beacons that transmit on the frequency band 406.0-406.1 MHz must use G1D emission. Use of...

  1. 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....

  2. 47 CFR 24.229 - Frequencies.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 2 2012-10-01 2012-10-01 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....

  3. 47 CFR 87.449 - Frequencies.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 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...

  4. 47 CFR 87.195 - Frequencies.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 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...

  5. 47 CFR 87.195 - Frequencies.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 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...

  6. 47 CFR 95.1113 - Frequency coordinator.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 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...

  7. 47 CFR 74.402 - Frequency assignment.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Frequency assignment. 74.402 Section 74.402....402 Frequency assignment. Operation on all channels listed in this section (except: frequencies 26.07 MHz, 26.11 MHz, and 26.45 MHz, and frequencies listed in paragraphs (a)(4) and (c)(1) of this...

  8. 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...

  9. 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...

  10. 47 CFR 74.638 - Frequency coordination.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Frequency coordination. 74.638 Section 74.638... Stations § 74.638 Frequency coordination. (a) Coordination of all frequency assignments for fixed stations... parties agree. Coordination of all frequency assignments for all mobile (temporary fixed) stations in...

  11. 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...

  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 74.1261 - Frequency tolerance.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 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 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...

  15. 47 CFR 73.754 - Frequency monitors.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 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...

  16. 47 CFR 74.402 - Frequency assignment.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Frequency assignment. 74.402 Section 74.402....402 Frequency assignment. Operation on all channels listed in this section (except: frequencies 26.07 MHz, 26.11 MHz, and 26.45 MHz, and frequencies listed in paragraphs (a)(4) and (c)(1) of this...

  17. 47 CFR 24.235 - Frequency stability.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 2 2012-10-01 2012-10-01 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....

  18. 47 CFR 73.754 - Frequency monitors.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 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...

  19. 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...

  20. 47 CFR 74.1261 - Frequency tolerance.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 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...

  1. 47 CFR 74.602 - Frequency assignment.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false Frequency assignment. 74.602 Section 74.602... Stations § 74.602 Frequency assignment. (a) The following frequencies are available for assignment to... to GSO FSS operations in the 12.75-13.25 GHz band. (1) Frequencies shown above between 2450 and...

  2. 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...

  3. 47 CFR 80.375 - Radiodetermination frequencies.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 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....

  4. 47 CFR 74.503 - Frequency selection.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 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...

  5. 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...

  6. 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...

  7. 47 CFR 74.561 - Frequency tolerance.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 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 74.402 - Frequency assignment.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Frequency assignment. 74.402 Section 74.402....402 Frequency assignment. Operation on all channels listed in this section (except: frequencies 26.07 MHz, 26.11 MHz, and 26.45 MHz, and frequencies listed in paragraphs (a)(4) and (c)(1) of this...

  9. 47 CFR 87.195 - Frequencies.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 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...

  10. 47 CFR 87.349 - Frequencies.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 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...

  11. 47 CFR 95.1401 - Frequency.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Frequency. 95.1401 Section 95.1401... SERVICES Personal Locator Beacons (PLB) § 95.1401 Frequency. The frequency band 406.0-406.1 MHz is an emergency and distress frequency band available for use by Personal Locator Beacons (PLBs). Personal...

  12. 47 CFR 74.638 - Frequency coordination.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false Frequency coordination. 74.638 Section 74.638... Stations § 74.638 Frequency coordination. (a) Coordination of all frequency assignments for fixed stations... parties agree. Coordination of all frequency assignments for all mobile (temporary fixed) stations in...

  13. 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...

  14. 47 CFR 5.403 - Frequencies.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 1 2013-10-01 2013-10-01 false Frequencies. 5.403 Section 5.403... Radio Licenses § 5.403 Frequencies. (a) Licensees may operate in any frequency band, including those above 38.6 GHz, except for frequency bands exclusively allocated to the passive services (including...

  15. 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...

  16. 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...

  17. 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...

  18. 47 CFR 87.475 - Frequencies.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Frequencies. 87.475 Section 87.475... Stations in the Radiodetermination Service § 87.475 Frequencies. (a) Frequency coordination. The Commission will assign frequencies to radionavigation land stations and radionavigation land test stations...

  19. 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...

  20. 47 CFR 74.602 - Frequency assignment.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false Frequency assignment. 74.602 Section 74.602... Stations § 74.602 Frequency assignment. (a) The following frequencies are available for assignment to... to GSO FSS operations in the 12.75-13.25 GHz band. (1) Frequencies shown above between 2450 and...

  1. 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...

  2. 47 CFR 18.301 - Operating frequencies.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 1 2012-10-01 2012-10-01 false Operating frequencies. 18.301 Section 18.301... Standards § 18.301 Operating frequencies. ISM equipment may be operated on any frequency above 9 kHz except as indicated in § 18.303. The following frequency bands, in accordance with § 2.106 of the rules,...

  3. 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....

  4. 47 CFR 95.853 - Frequency segments.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 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...

  5. 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...

  6. 47 CFR 95.1401 - Frequency.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Frequency. 95.1401 Section 95.1401... SERVICES Personal Locator Beacons (PLB) § 95.1401 Frequency. The frequency band 406.0-406.1 MHz is an emergency and distress frequency band available for use by Personal Locator Beacons (PLBs). Personal...

  7. 47 CFR 74.503 - Frequency selection.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 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...

  8. 47 CFR 95.1113 - Frequency coordinator.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 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...

  9. 47 CFR 74.638 - Frequency coordination.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Frequency coordination. 74.638 Section 74.638... Stations § 74.638 Frequency coordination. (a) Coordination of all frequency assignments for fixed stations... parties agree. Coordination of all frequency assignments for all mobile (temporary fixed) stations in...

  10. 47 CFR 87.217 - Frequencies.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 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...

  11. 47 CFR 87.351 - Frequency changes.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 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...

  12. 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...

  13. 47 CFR 18.301 - Operating frequencies.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false Operating frequencies. 18.301 Section 18.301... Standards § 18.301 Operating frequencies. ISM equipment may be operated on any frequency above 9 kHz except as indicated in § 18.303. The following frequency bands, in accordance with § 2.106 of the rules,...

  14. 47 CFR 95.1401 - Frequency.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Frequency. 95.1401 Section 95.1401... SERVICES Personal Locator Beacons (PLB) § 95.1401 Frequency. The frequency band 406.0-406.1 MHz is an emergency and distress frequency band available for use by Personal Locator Beacons (PLBs). Personal...

  15. 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...

  16. 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....

  17. 47 CFR 24.229 - Frequencies.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 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....

  18. 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...

  19. 47 CFR 80.1077 - Frequencies.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Frequencies. 80.1077 Section 80.1077... Frequencies. The following table describes the frequencies used in the Global Maritime Distress and Safety... radiotelephony 156.8 MHz and one other 156-174 MHz frequency 9 GHz radar transponders 9200-9500 MHz. 1...

  20. 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...