Assessments at multiple levels of biological organization allow for an integrative determination of physiological tolerances to turbidity in an endangered fish species

OpenAIRE

Hasenbein, Matthias; Fangue, Nann A.; Geist, Juergen; Komoroske, Lisa M.; Truong, Jennifer; McPherson, Rina; Connon, Richard E.

2016-01-01

Turbidity can influence trophic levels by altering species composition and can potentially affect fish feeding strategies and predator?prey interactions. The estuarine turbidity maximum, described as an area of increased suspended particles, phytoplankton and zooplankton, generally represents a zone with higher turbidity and enhanced food sources important for successful feeding and growth in many fish species. The delta smelt (Hypomesus transpacificus) is an endangered, pelagic fish species ...

Turbidity maximum formation in a well-mixed macrotidal estuary : The role of tidal pumping

NARCIS (Netherlands)

Yu, Q.; Wang, Y.; Gao, J.; Gao, S.; Flemming, B.

2014-01-01

Traditionally, vertical circulation (induced by gravity circulation and tidal straining), tidal pumping, and resuspension are suggested as the major processes for the formation and maintenance of the estuarine turbidity maximum (ETM). Due to strong mixing, tidal pumping is considered as the

Loire and Gironde turbid plumes: Characterization and influence on thermohaline properties

Science.gov (United States)

Costoya, X.; Fernández-Nóvoa, D.; deCastro, M.; Gómez-Gesteira, M.

2017-12-01

Knowledge and predictability of turbid river plumes is of great importance because they modulate the properties of the seawater adjacent to river mouths. The Loire and Gironde Rivers form the most important plumes in the Bay of Biscay, as they provide > 75% of total runoff. The development of the turbid plume under the influence of its main drivers was analyzed using Moderate Resolution Imaging Spectroradiometer satellite data from the period 2003-2015. River discharge was found to be the main driver, followed by wind, which also had an important effect in modulating the turbid plume during periods of high river discharge. Seaward and upwelling favorable winds enhanced the dispersion of plumes on seawater, whereas landward and downwelling favorable winds limited mixing with the adjacent ocean water. The maximum extension of the turbid plume was reached under landward winds. In addition, the spatio-temporal evolution of the East Atlantic pattern and the North Atlantic Oscillation was observed to affect the dynamics of plumes: positive values of both indices favored a greater extension of the plume. Thermohaline properties differed inside and outside the area affected by both rivers. In particular, these rivers maintain winter stratification inside the turbid plume, which results in a different warming ratio when compared with the adjacent ocean.

Feedback between residual circulations and sediment distribution in highly turbid estuaries: an analytical model

NARCIS (Netherlands)

Talke, S.A.|info:eu-repo/dai/nl/304823554; de Swart, H.E.|info:eu-repo/dai/nl/073449725; Schuttelaars, H.|info:eu-repo/dai/nl/164035656

2009-01-01

Motivated by field studies of the Ems estuary which show longitudinal gradients in bottom sediment concentration as high as O(0.01 kg/m4), we develop an analytical model for estuarine residual circulation based on currents from salinity gradients, turbidity gradients, and freshwater discharge.

Wind-Driven Waves in Tampa Bay, Florida

Science.gov (United States)

Gilbert, S. A.; Meyers, S. D.; Luther, M. E.

2002-12-01

Turbidity and nutrient flux due to sediment resuspension by waves and currents are important factors controlling water quality in Tampa Bay. During December 2001 and January 2002, four Sea Bird Electronics SeaGauge wave and tide recorders were deployed in Tampa Bay in each major bay segment. Since May 2002, a SeaGauge has been continuously deployed at a site in middle Tampa Bay as a component of the Bay Regional Atmospheric Chemistry Experiment (BRACE). Initial results for the summer 2002 data indicate that significant wave height is linearly dependent on wind speed and direction over a range of 1 to 12 m/s. The data were divided into four groups according to wind direction. Wave height dependence on wind speed was examined for each group. Both northeasterly and southwesterly winds force significant wave heights that are about 30% larger than those for northwesterly and southeasterly winds. This difference is explained by variations in fetch due to basin shape. Comparisons are made between these observations and the results of a SWAN-based model of Tampa Bay. The SWAN wave model is coupled to a three-dimensional circulation model and computes wave spectra at each model grid cell under observed wind conditions and modeled water velocity. When SWAN is run without dissipation, the model results are generally similar in wave period but about 25%-50% higher in significant wave height than the observations. The impact of various dissipation mechanisms such as bottom drag and whitecapping on the wave state is being investigated. Preliminary analyses on winter data give similar results.

Interactive drivers of activity in a free-ranging estuarine predator.

Directory of Open Access Journals (Sweden)

Matthew D Taylor

Full Text Available Animal activity patterns evolve as an optimal balance between energy use, energy acquisition, and predation risk, so understanding how animals partition activity relative to extrinsic environmental fluctuations is central to understanding their ecology, biology and physiology. Here we use accelerometry to examine the degree to which activity patterns of an estuarine teleost predator are driven by a series of rhythmic and arrhythmic environmental fluctuations. We implanted free-ranging bream Acanthopagrus australis with acoustic transmitters that measured bi-axial acceleration and pressure (depth, and simultaneously monitored a series of environmental variables (photosynthetically active radiation, tidal height, temperature, turbidity, and lunar phase for a period of approximately four months. Linear modeling showed an interaction between fish activity, light level and tidal height; with activity rates also negatively correlated with fish depth. These patterns highlight the relatively-complex trade-offs that are required to persist in highly variable environments. This study demonstrates how novel acoustic sensor tags can reveal interactive links between environmental cycles and animal behavior.

Wind driven mobile charging of automobile battery- A case study ...

African Journals Online (AJOL)

This paper deals with implementation of mobile wind driven generator technology to produce electricity in charging of two wheeler (12V) automobile battery. The use of PWM methodology with pulse charging method at a constant rate has been adopted for this purpose. The low speed PMSG driven by wind at speed of ...

Comparison of the different methods for the recovery of suspended matter from estuarine waters: deposition, filtration and centrifugation

Energy Technology Data Exchange (ETDEWEB)

Etcheber, H; Jouanneau, J M

1980-12-01

The advantages and disadvantages of three methods used to recover heavy metals from estuarine waters are compared. Deposition, filtration, and centrifugation were used on samples from the Gironde estuary of France. Recovery by deposition is satisfactory in cases of flocculation and high turbidity. Centrifugation is reliable for the determination of several elements in zones of low turbidity. (12 references, 4 tables)

Rocky intertidal macrobenthic communities across a large-scale estuarine gradient

Directory of Open Access Journals (Sweden)

Luis Giménez

2010-03-01

Full Text Available We evaluated relationships between (1 salinity and species richness and (2 frontal zones and community structure for the rocky intertidal macrobenthic community of the Uruguayan coast. A large-scale sampling design (extent ~500 km covering 9 rocky shores across 3 intertidal levels was performed between September and November 2002. The linear relationship between salinity and species richness (minimum at the freshwater extreme and the lack of correlation between variation in salinity and richness rejected two previous empirical models, explaining variations in species richness along the salinity gradient. Other factors (e.g. turbidity may explain this discrepancy. The estuarine front defined two communities—freshwater and estuarine-marine—differing in species composition and richness. The freshwater community was characterised by low richness and few individuals confined to crevices or tide pools, and must be structured by physical processes (e.g. desiccation; the estuarine-marine community, with individuals occupying almost all available substrata, must be structured by both physical and biological processes. A marine front, separating estuarine and marine habitats, had a weak effect on community structure although estuarine and marine assemblages differed according to species characterising different functional groups. We conclude that the position of the estuarine frontal zones is important for explaining large-scale patterns of community structure in the study area.

Relationships between aquatic vegetation and water turbidity: A field survey across seasons and spatial scales.

Science.gov (United States)

Austin, Åsa N; Hansen, Joakim P; Donadi, Serena; Eklöf, Johan S

2017-01-01

Field surveys often show that high water turbidity limits cover of aquatic vegetation, while many small-scale experiments show that vegetation can reduce turbidity by decreasing water flow, stabilizing sediments, and competing with phytoplankton for nutrients. Here we bridged these two views by exploring the direction and strength of causal relationships between aquatic vegetation and turbidity across seasons (spring and late summer) and spatial scales (local and regional), using causal modeling based on data from a field survey along the central Swedish Baltic Sea coast. The two best-fitting regional-scale models both suggested that in spring, high cover of vegetation reduces water turbidity. In summer, the relationships differed between the two models; in the first model high vegetation cover reduced turbidity; while in the second model reduction of summer turbidity by high vegetation cover in spring had a positive effect on summer vegetation which suggests a positive feedback of vegetation on itself. Nitrogen load had a positive effect on turbidity in both seasons, which was comparable in strength to the effect of vegetation on turbidity. To assess whether the effect of vegetation was primarily caused by sediment stabilization or a reduction of phytoplankton, we also tested models where turbidity was replaced by phytoplankton fluorescence or sediment-driven turbidity. The best-fitting regional-scale models suggested that high sediment-driven turbidity in spring reduces vegetation cover in summer, which in turn has a negative effect on sediment-driven turbidity in summer, indicating a potential positive feedback of sediment-driven turbidity on itself. Using data at the local scale, few relationships were significant, likely due to the influence of unmeasured variables and/or spatial heterogeneity. In summary, causal modeling based on data from a large-scale field survey suggested that aquatic vegetation can reduce turbidity at regional scales, and that high

Relationships between aquatic vegetation and water turbidity: A field survey across seasons and spatial scales.

Directory of Open Access Journals (Sweden)

Åsa N Austin

Full Text Available Field surveys often show that high water turbidity limits cover of aquatic vegetation, while many small-scale experiments show that vegetation can reduce turbidity by decreasing water flow, stabilizing sediments, and competing with phytoplankton for nutrients. Here we bridged these two views by exploring the direction and strength of causal relationships between aquatic vegetation and turbidity across seasons (spring and late summer and spatial scales (local and regional, using causal modeling based on data from a field survey along the central Swedish Baltic Sea coast. The two best-fitting regional-scale models both suggested that in spring, high cover of vegetation reduces water turbidity. In summer, the relationships differed between the two models; in the first model high vegetation cover reduced turbidity; while in the second model reduction of summer turbidity by high vegetation cover in spring had a positive effect on summer vegetation which suggests a positive feedback of vegetation on itself. Nitrogen load had a positive effect on turbidity in both seasons, which was comparable in strength to the effect of vegetation on turbidity. To assess whether the effect of vegetation was primarily caused by sediment stabilization or a reduction of phytoplankton, we also tested models where turbidity was replaced by phytoplankton fluorescence or sediment-driven turbidity. The best-fitting regional-scale models suggested that high sediment-driven turbidity in spring reduces vegetation cover in summer, which in turn has a negative effect on sediment-driven turbidity in summer, indicating a potential positive feedback of sediment-driven turbidity on itself. Using data at the local scale, few relationships were significant, likely due to the influence of unmeasured variables and/or spatial heterogeneity. In summary, causal modeling based on data from a large-scale field survey suggested that aquatic vegetation can reduce turbidity at regional scales

Monitoring suspended sediments and turbidity in Sahelian basins

Science.gov (United States)

Robert, Elodie; Grippa, Manuela; Kergoat, Laurent; Martinez, Jean-Michel; Pinet, Sylvain; Nogmana, Soumaguel

2017-04-01

interannual scales with the NIR reflectance. The Agoufou pond displays a strong seasonal evolutions, and also the highest values of turbidity and SSSC (as high as 4200 mg/l).Turbidity increases from the first rains in June with a maximum observed in July and August and then declines from October onwards. The 2015 and 2016 dry seasons however differ markedly, with a secondary maximum of SSSC in February occurring in 2016, possibly caused by wind-driven sediments remobilization or cattle trampling. The Niger River in Niamey displays a rapid increase in turbidity between mid-June and late August associated to the 'red' flood, with a maximum in late July-early August and then a sharp decline associated with the black flood. Overall, the high turbidity observed at these sites indicates clear risks for human health. The methods developed here for the AMMA-CATCH, RBV sites will be applied to all inland waters in West Africa.

Mechanics of interrill erosion with wind-driven rain

Science.gov (United States)

The vector physics of wind-driven rain (WDR) differs from that of wind-free rain, and the interrill soil detachment equations in the Water Erosion Prediction Project (WEPP) model were not originally developed to deal with this phenomenon. This article provides an evaluation of the performance of the...

Directly driven generators for wind power applications

Energy Technology Data Exchange (ETDEWEB)

Lampola, P [Helsinki Univ. of Technology, Espoo (Finland). Lab. of Electromechanics

1996-12-31

The article deals with an analysis of directly driven, low-speed wind generators. The generators studied were a permanent-magnet synchronous machine and an asynchronous machine. The machines were compared with a typical generator of a wind power plant. The electromagnetic optimization of the machines was done by the finite element method. The rated power of the generators was 500 kW and the rotational speed was 40 rpm. (author)

Directly driven generators for wind power applications

Energy Technology Data Exchange (ETDEWEB)

Lampola, P. [Helsinki Univ. of Technology, Espoo (Finland). Lab. of Electromechanics

1995-12-31

The article deals with an analysis of directly driven, low-speed wind generators. The generators studied were a permanent-magnet synchronous machine and an asynchronous machine. The machines were compared with a typical generator of a wind power plant. The electromagnetic optimization of the machines was done by the finite element method. The rated power of the generators was 500 kW and the rotational speed was 40 rpm. (author)

Wind-Wave Effects on Vertical Mixing in Chesapeake Bay, USA: comparing observations to second-moment closure predictions.

Science.gov (United States)

Fisher, A. W.; Sanford, L. P.; Scully, M. E.

2016-12-01

Coherent wave-driven turbulence generated through wave breaking or nonlinear wave-current interactions, e.g. Langmuir turbulence (LT), can significantly enhance the downward transfer of momentum, kinetic energy, and dissolved gases in the oceanic surface layer. There are few observations of these processes in the estuarine or coastal environments, where wind-driven mixing may co-occur with energetic tidal mixing and strong density stratification. This presents a major challenge for evaluating vertical mixing parameterizations used in modeling estuarine and coastal dynamics. We carried out a large, multi-investigator study of wind-driven estuarine dynamics in the middle reaches of Chesapeake Bay, USA, during 2012-2013. The center of the observational array was an instrumented turbulence tower with both atmospheric and marine turbulence sensors as well as rapidly sampled temperature and conductivity sensors. For this paper, we examined the impacts of surface gravity waves on vertical profiles of turbulent mixing and compared our results to second-moment turbulence closure predictions. Wave and turbulence measurements collected from the vertical array of Acoustic Doppler Velocimeters (ADVs) provided direct estimates of the dominant terms in the TKE budget and the surface wave field. Observed dissipation rates, TKE levels, and turbulent length scales are compared to published scaling relations and used in the calculation of second-moment nonequilibrium stability functions. Results indicate that in the surface layer of the estuary, where elevated dissipation is balanced by vertical divergence in TKE flux, existing nonequilibrium stability functions underpredict observed eddy viscosities. The influences of wave breaking and coherent wave-driven turbulence on modeled and observed stability functions will be discussed further in the context of turbulent length scales, TKE and dissipation profiles, and the depth at which the wave-dominated turbulent transport layer

Physical processes affecting turbidity in a tidal marsh across a range of time scales

Science.gov (United States)

Arnold, W.; Poindexter, C.

2016-12-01

The direction of net suspended sediment flux, whether into or out of a tidal marsh, can determine whether a marsh is aggrading or eroding. Measuring net suspended sediment fluxes or attributing trends in these fluxes to a particular physical processes is challenging because suspended sediment concentrations are highly variable in time. We used singular spectrum analysis for time series with missing data (SSAM) to observe the relative effects on turbidity of physical processes occurring on different time scales at the Rush Ranch Open Space Preserve. This Preserve covers the largest contiguous area of full-tidal marsh remaining within Suisun Bay, the eastern most subembayment of San Francisco Bay. A long-term monitoring station at First Mallard Slough within the Preserve measures turbidity. Our analysis of of this turbidity record isolated the contribution to total variance from different tides and from annual cycles of San Francisco Bay freshwater inflow, sediment deposition and wind-driven sediment resuspension. Surprisingly, the contribution from diurnal and semidiurnal tidal constituents (30%) was smaller than the contribution from annual cycles of freshwater inflow, sediment deposition and resuspension (38%). This result contrasts with the original implementation of SSAM to suspended sediment concentration, which was conducted in the central San Francisco Bay. This previous work indicated a significant yet smaller contribution (13%) to total suspended sediment concentration variance from annual cycles (Schoellhamer, D. H., 2002, Continental Shelf Research., 22, 1857-1866). The reason for the contrast relates in part to the location of the First Mallard Slough more than 10 km along the tidal channel network from Suisun Bay. At this location, the lowest frequency variation in suspended sediment is accentuated. Annual peaks in turbidity at First Mallard depend not only on spring and summer wind-driven resuspension of sediment in San Pablo Bay but also its co

Estuarine Turbidity Maxima and Variations of Aggregate Parameters in the Cam-Nam Trieu Estuary, North Vietnam, in Early Wet Season

Directory of Open Access Journals (Sweden)

Vu Duy Vinh

2018-01-01

Full Text Available This study aims at exploring the characteristic parameters of the Estuarine Turbidity Maxima (ETM and at investigating their tidal variations within the Cam-Nam Trieu estuary (North Vietnam during the early wet season. Six longitudinal river transects were performed at spring tide. Two types of ETM were observed: an upper well mixed ETM with high Suspended Particulate Matter (SPM concentrations up to the surface at low salinity (0.11 to <1 psu, and a lower ETM confined in a bottom layer over stratified waters at salinities between ~1 psu and 15 psu. Their length depended on the longitudinal salinity gradient and was highest at low tide than at high tide. D50 of the flocs varied between 35 and 90 μm, their excess of density between 60 and 300 kg m−3 and their settling velocity ranged from 0.07 to 0.55 mm s−1 with values between 0.12 and 0.40 mm s−1 in the core of ETMs. The average fractal dimension of flocs was estimated to vary between 1.93 (at high tide to 2.04 (at low tide.

Estimating the Probability of Wind Ramping Events: A Data-driven Approach

OpenAIRE

Wang, Cheng; Wei, Wei; Wang, Jianhui; Qiu, Feng

2016-01-01

This letter proposes a data-driven method for estimating the probability of wind ramping events without exploiting the exact probability distribution function (PDF) of wind power. Actual wind data validates the proposed method.

Seasonal dynamics of the genus: Planktoniella Schutt in the estuarine waters of Indian Sundarbans.

Science.gov (United States)

Sekh, Sanoyaz; Biswas, Biswajit; Mandal, Manjushree; Sarkar, Neera Sen

2016-01-01

The study highlights the dynamics and morphological characteristics of the Genus Planktoniella Schutt. The two available species P. sol (Wallich) Schutt. and P. blanda (Schmidt) Syvertsen and Hasle are important components of the phytoplankton assemblage in the estuarine system of Indian Sundarbans and also marine systems elsewhere. The sampling sites for the purpose of this study include four different spots along a riverine stretch in the estuarine region adjacent to the Tiger Reserve in the Indian Sundarbans flowing into the Bay of Bengal. Integrated phytoplankton samples were preserved for the purpose from composite water samples from each site. The water samples were analysed in field for determining pH, temperature, salinity, conductivity, TDS, turbidity and DO and subsequent to treatment and processing, the samples were microscopically analysed in the laboratory. Significant negative correlation of cell count of both species found with respect to temperature and turbidity. P. sol versus temperature (significant at α = 0.01, p = 0.001) and P. blanda versus temperature (significant at α = 0.05, p = 0.037); P. sol versus turbidity (at α = 0.05, p = 0.019) and P. blanda versus turbidity (at α = 0.05, p = 0.019). Significant positive correlation found with respect to DO and as correlation between the two species themselves. A model has been generated for each of the two species with temperature, turbidity and DO as predictor variables and the two species of Planktoniella as response variables. The influence of other dominant phytoplankton in the samples has also been considered with Pearson correlation computed for each set of species.

Mechanics of Interrill Erosion with Wind-Driven Rain (WDR)

Science.gov (United States)

This article provides an evaluation analysis for the performance of the interrill component of the Water Erosion Prediction Project (WEPP) model for Wind-Driven Rain (WDR) events. The interrill delivery rates (Di) were collected in the wind tunnel rainfall simulator facility of the International Cen...

Seasonal variations in suspended-sediment dynamics in the tidal reach of an estuarine tributary

Science.gov (United States)

Downing-Kunz, Maureen A.; Schoellhamer, David H.

2013-01-01

Quantifying sediment supply from estuarine tributaries is an important component of developing a sediment budget, and common techniques for estimating supply are based on gages located above tidal influence. However, tidal interactions near tributary mouths can affect the magnitude and direction of sediment supply to the open waters of the estuary. We investigated suspended-sediment dynamics in the tidal reach of Corte Madera Creek, an estuarine tributary of San Francisco Bay, using moored acoustic and optical instruments. Flux of both water and suspended-sediment were calculated from observed water velocity and turbidity for two periods in each of wet and dry seasons during 2010. During wet periods, net suspended-sediment flux was seaward; tidally filtered flux was dominated by the advective component. In contrast, during dry periods, net flux was landward; tidally filtered flux was dominated by the dispersive component. The mechanisms generating this landward flux varied; during summer we attributed wind–wave resuspension in the estuary and subsequent transport on flood tides, whereas during autumn we attributed increased spring tide flood velocity magnitude leading to local resuspension. A quadrant analysis similar to that employed in turbulence studies was developed to summarize flux time series by quantifying the relative importance of sediment transport events. These events are categorized by the direction of velocity (flood vs. ebb) and the magnitude of concentration relative to tidally averaged conditions (relatively turbid vs. relatively clear). During wet periods, suspended-sediment flux was greatest in magnitude during relatively turbid ebbs, whereas during dry periods it was greatest in magnitude during relatively turbid floods. A conceptual model was developed to generalize seasonal differences in suspended-sediment dynamics; model application to this study demonstrated the importance of few, relatively large events on net suspended-sediment flux

Influence of main forcing affecting the Tagus turbid plume under high river discharges using MODIS imagery.

Science.gov (United States)

Fernández-Nóvoa, D; Gómez-Gesteira, M; Mendes, R; deCastro, M; Vaz, N; Dias, J M

2017-01-01

The role of river discharge, wind and tide on the extension and variability of the Tagus River plume was analyzed from 2003 to 2015. This study was performed combining daily images obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor located onboard the Aqua and Terra satellites. Composites were generated by averaging pixels with the same forcing conditions. River discharge shows a strong relation with the extension of the Tagus plume. The plume grows with the increasing river discharge and express a two day lag caused by the long residence time of water within the estuary. The Tagus turbid plume was found to be smaller under northerly and easterly winds, than under southerly and westerly winds. It is suggested that upwelling favoring winds provoke the offshore movement of the plume material with a rapidly decrease in turbidity values whereas downwelling favoring winds retain plume material in the north coast close to the Tagus mouth. Eastern cross-shore (oceanward) winds spread the plume seaward and to the north following the coast geometry, whereas western cross-shore (landward) winds keep the plume material in both alongshore directions occupying a large part of the area enclosed by the bay. Low tides produce larger and more turbid plumes than high tides. In terms of fortnightly periodicity, the maximum plume extension corresponding to the highest turbidity is observed during and after spring tides. Minimum plume extension associated with the lowest turbidity occurs during and after neap tides.

Influence of main forcing affecting the Tagus turbid plume under high river discharges using MODIS imagery.

Directory of Open Access Journals (Sweden)

D Fernández-Nóvoa

Full Text Available The role of river discharge, wind and tide on the extension and variability of the Tagus River plume was analyzed from 2003 to 2015. This study was performed combining daily images obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS sensor located onboard the Aqua and Terra satellites. Composites were generated by averaging pixels with the same forcing conditions. River discharge shows a strong relation with the extension of the Tagus plume. The plume grows with the increasing river discharge and express a two day lag caused by the long residence time of water within the estuary. The Tagus turbid plume was found to be smaller under northerly and easterly winds, than under southerly and westerly winds. It is suggested that upwelling favoring winds provoke the offshore movement of the plume material with a rapidly decrease in turbidity values whereas downwelling favoring winds retain plume material in the north coast close to the Tagus mouth. Eastern cross-shore (oceanward winds spread the plume seaward and to the north following the coast geometry, whereas western cross-shore (landward winds keep the plume material in both alongshore directions occupying a large part of the area enclosed by the bay. Low tides produce larger and more turbid plumes than high tides. In terms of fortnightly periodicity, the maximum plume extension corresponding to the highest turbidity is observed during and after spring tides. Minimum plume extension associated with the lowest turbidity occurs during and after neap tides.

Data Driven Modelling of the Dynamic Wake Between Two Wind Turbines

DEFF Research Database (Denmark)

Knudsen, Torben; Bak, Thomas

2012-01-01

turbine. This paper establishes flow models relating the wind speeds at turbines in a farm. So far, research in this area has been mainly based on first principles static models and the data driven modelling done has not included the loading of the upwind turbine and its impact on the wind speed downwind......Wind turbines in a wind farm, influence each other through the wind flow. Downwind turbines are in the wake of upwind turbines and the wind speed experienced at downwind turbines is hence a function of the wind speeds at upwind turbines but also the momentum extracted from the wind by the upwind....... This paper is the first where modern commercial mega watt turbines are used for data driven modelling including the upwind turbine loading by changing power reference. Obtaining the necessary data is difficult and data is therefore limited. A simple dynamic extension to the Jensen wake model is tested...

Impact of (α, n) reactions on the nucleosynthesis in neutrino-driven winds

Energy Technology Data Exchange (ETDEWEB)

Bliss, Julia [Institut fuer Kernphysik, TU Darmstadt (Germany); Arcones, Almudena [Institut fuer Kernphysik, TU Darmstadt (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung GmbH (Germany); Montes, Fernando; Pereira, Jorge [National Superconducting Cyclotron Laboratory, Michigan State University (United States); Joint Institute for Nuclear Astrophysics (United States)

2015-07-01

Neutrino-driven winds that follow core-collapse supernova explosions are an exciting astrophysical site for the synthesis of heavy elements. Although recent hydrodynamical simulations show that the conditions in the wind are not extreme enough for a r-process up to uranium, neutrino-driven winds may be the astrophysical site where lighter heavy elements between Sr and Ag are produced. However, it is still not clear if the conditions in the wind are slightly neutron-rich, proton-rich or turn proton-rich for some time. In neutron-rich winds, (α,n) reactions are key to move matter beyond the Fe-group towards heavier elements. Due to the deficit of experimental information, the relevant reaction rates have mostly been calculated with codes based on Hauser-Feshbach models. Although these codes have been cross-checked with experimental data in regions close to stability, their accuracy is questionable as one moves towards more exotic regions. We present the impact of (α,n) reactions on the nucleosynthesis of elements between Sr and Ag in neutrino-driven winds.

Dynamic Performance of the Standalone Wind Power Driven Heat Pump

OpenAIRE

H. Li; P.E. Campana; S. Berretta; Y. Tan; J. Yan

2016-01-01

Reducing energy consumption and increasing use of renewable energyin the building sector arecrucial to the mitigation of climate change. Wind power driven heat pumps have been considered as a sustainable measure to supply heat for detached houses, especially those that even don’t have access to the grid. This work is to investigate the dynamic performance of a heat pump system directly driven by a wind turbine. The heat demand of a detached single family house was simulated in details. Accord...

An Overview of Wind-Driven Rovers for Planetary Exploration

Science.gov (United States)

Hajos, Gregory A.; Jones, Jack A.; Behar, Alberto; Dodd, Micheal

2005-01-01

The use of in-situ propulsion is considered enabling technology for long duration planetary surface missions. Most studies have focused on stored energy from chemicals extracted from the soil or the use of soil chemicals to produce photovoltaic arrays. An older form of in-situ propulsion is the use of wind power. Recent studies have shown potential for wind driven craft for exploration of Mars, Titan and Venus. The power of the wind, used for centuries to power wind mills and sailing ships, is now being applied to modern land craft. Efforts are now underway to use the wind to push exploration vehicles on other planets and moons in extended survey missions. Tumbleweed rovers are emerging as a new type of wind-driven science platform concept. Recent investigations by the National Aeronautics and Space Administration (NASA) and Jet Propulsion Laboratory (JPL) indicate that these light-weight, mostly spherical or quasi-spherical devices have potential for long distance surface exploration missions. As a power boat has unique capabilities, but relies on stored energy (fuel) to move the vessel, the Tumbleweed, like the sailing ships of the early explorers on earth, uses an unlimited resource the wind to move around the surface of Mars. This has the potential to reduce the major mass drivers of robotic rovers as well as the power generation and storage systems. Jacques Blamont of JPL and the University of Paris conceived the first documented Mars wind-blown ball in 1977, shortly after the Viking landers discovered that Mars has a thin CO2 atmosphere with relatively strong winds. In 1995, Jack Jones, et al, of JPL conceived of a large wind-blown inflated ball for Mars that could also be driven and steered by means of a motorized mass hanging beneath the rolling axis of the ball. A team at NASA Langley Research Center started a biomimetic Tumbleweed design study in 1998. Wind tunnel and CFD analysis were applied to a variety of concepts to optimize the aerodynamic

Galactic Winds Driven by Supernovae and Radiation Pressure: Theory and Simulations

Science.gov (United States)

Zhang, Dong; Davis, Shane

2018-01-01

Galactic winds are ubiquitous in most rapidly star-forming galaxies. They are crucial to the process of galaxy formation and evolution, regulating star formation, shaping the stellar mass function and the mass-metallicity relation, and enriching the intergalactic medium with metals. Although important, the physics of galactic winds is still unclear. Winds may be driven by many mechanisms including overlapping supernovae explosions, radiation pressure of starlight on dust grains, and cosmic rays. However, the growing observations of multiphase structure in galactic winds in a large number of galaxies have not been well explained by any models. In this talk I will focus on the models of supernova- and radiation-pressure-driven winds. Using the state-of-the-art numerical simulations, I will assess the relative merits of these driving mechanisms for accelerating cold and warm clouds to observed velocities, and momentum flux boost during wind propagation.

Theory of radiatively driven stellar winds. I. A physical interpretation

International Nuclear Information System (INIS)

Abbott, D.C.

1980-01-01

This series of papers extends the line-driven wind theory of Castor, Abbott, and Klein (CAK). The present paper develops a physical interpretation of line-driven flows using analytic methods. Numerical results will follow in two subsequent papers

Triggering of frequent turbidity currents in Monterey Canyon and the role of antecedent conditioning

Science.gov (United States)

Clare, M. A.; Rosenberger, K. J.; Talling, P.; Barry, J.; Maier, K. L.; Parsons, D. R.; Simmons, S.; Gales, J. A.; Gwiazda, R.; McGann, M.; Paull, C. K.

2017-12-01

Turbidity currents pose a hazard to seafloor infrastructure, deliver organic carbon and nutrients to deep-sea communities, and form economically important deposits. Thus, determining the tempo of turbidity current activity and whether different triggers result in different flow modes is important. Identification of specific triggers is challenging, however, because most studies of turbidity currents are based on their deposits. New direct monitoring of flows and environmental conditions provides the necessary temporal constraints to identify triggering mechanisms. The Coordinated Canyon Experiment (CCE) in Monterey Canyon, offshore California is the most ambitious attempt yet to measure turbidity flows and their triggers. The CCE provides precise constraint on flow timing, initiation, and potential triggers based on measurements at 7 different instrumented moorings and 2 metocean buoys. Fifteen turbidity flows were measured in 18 months; with recorded velocities >8 m/s and run-outs of up to 50 km. Presence of live estuarine foraminifera within moored sediment traps suggests that that flows originated in water depths of Turbidity currents are thought to be triggered by processes including earthquakes, river floods and storm waves. Here we analyse seismicity, local river discharge, internal tides, wave height, direction and period data. We identify no clear control of any of these individual variables on flow timing. None of the recorded earthquakes (

Wind-driven stand-alone DFIG with battery and pumped hydro ...

Indian Academy of Sciences (India)

Renewable energy electric conversion system; induction generators; wind power generation; energy storage; power converters. ... converter, (ii) wide speed operation of wind-driven DFIG, (iii) reduced battery capacity, (iv) high energy storage using PHSP and (v) availability of continuous power to the isolated loads.

Tidally-driven Surface Flow in a Georgia Estuarine Saltmarsh

Science.gov (United States)

Young, D.; Bruder, B. L.; Haas, K. A.; Webster, D. R.

2016-02-01

Estuarine saltmarshes are diverse, valuable, and productive ecosystems. Vegetation dampens wave and current energy, thereby allowing the estuaries to serve as a nursery habitat for shellfish and fish species. Tidally-driven flow transports nutrients into and out of the estuary, nourishing inshore and offshore vegetation and animals. The effects of vegetation on the marsh hydrodynamics and on the estuary creek and channel flow are, unfortunately, poorly understood, and the knowledge that does exist primarily originates from modeling studies. Field studies addressing marsh surface flows are limited due to the difficulty of accurately measuring the water surface elevation and acquiring concurrent velocity measurements in the dense marsh vegetation. This study partially bridges the gap between the model observations of marsh flow driven by water surface elevation gradients and flume studies of flow through vegetation. Three current meters and three pressure transducers were deployed for three days along a transect perpendicular to the main channel (Little Ogeechee River) in a saltmarsh adjacent to Rose Dhu Island (Savannah, Georgia, USA). The pressure transducer locations were surveyed daily with static GPS yielding highly accurate water surface elevation data. During flood and ebb tide, water surface elevation differences between the marsh and Little Ogeechee River were observed up to 15 cm and pressure gradients were observed up to 0.0017 m of water surface elevation drop per m of linear distance. The resulting channel-to-saltmarsh pressure gradients substantially affected tidal currents at all current meters. At one current meter, the velocity was nearly perpendicular to the Little Ogeechee River bank. The velocity at this location was effectively modeled as a balance between the pressure gradient and marsh vegetation-induced drag force using the Darcy-Weisbach/Lindner's equations developed for flow-through-vegetation analysis in open channel flow.

Determination of Linke turbidity factor from solar radiation measurement in northern Tunisia

International Nuclear Information System (INIS)

Chaabane, M.; Masmoudi, M.; Medhioub, K.

2004-01-01

The attenuation of solar radiation through a real atmosphere versus that through a clean dry atmosphere gives an indication of the atmospheric turbidity. Study of atmospheric turbidity is important in meteorology, climatology and for monitoring of atmospheric pollution. The Linke turbidity factor refers to the whole spectrum, that is, overall spectrally integrated attenuation, which includes presence of gaseous water vapour and aerosols. In this work, a procedure for calculation of Linke turbidity factor is adopted using pyrheliometric measurements in a coastal tourist location in Tunisia (Sidi Bou Said), during three summer months (June, July and August 1999). Real diurnal and monthly variations of the T L turbidity factor are found in the three studied months, with a maximum in August afternoon and a minimum in July morning. The increase of T L is an indication for increasing atmospheric turbidity level (pollution). The correlation between atmospheric turbidity and the local weather conditions shows that this increase is essentially due to the heavy water vapour content of maritime air masses, carried by the north-eastern winds prevalent during the afternoon. A second pollution source is the dust content of the continental air masses carried by western and southern winds prevalent in the morning. Next to this can be added the influence of traffic at rush hours and during the afternoon of summer holidays. (Author)

Wind-driven Water Bodies : a new paradigm for lake geology

Science.gov (United States)

Nutz, A.; Schuster, M.; Ghienne, J. F.; Roquin, C.; Bouchette, F. A.

2015-12-01

In this contribution we emphasize the importance in some lakes of wind-related hydrodynamic processes (fair weather waves, storm waves, and longshore, cross-shore and bottom currents) as a first order forcing for clastics remobilization and basin infill. This alternative view contrasts with more classical depositional models for lakes where fluvial-driven sedimentation and settling dominates. Here we consider three large lakes/paleo-lakes that are located in different climatic and geodynamic settings: Megalake Chad (north-central Africa), Lake Saint-Jean (Québec, Canada), and Lake Turkana (Kenya, East African Rift System). All of these three lake systems exhibit well developed modern and ancient high-energy littoral morphosedimentary structures which directly derive from wind-related hydrodynamics. The extensive paleo-shorelines of Megalake Chad are composed of beach-foredune ridges, spits, wave-dominated deltas, barriers, and wave-ravinment surface. For Lake Saint-Jean the influence of wind is also identified below the wave-base at lake bottom from erosional surfaces, and sediment drifts. In the Lake Turkana Basin, littoral landforms and deposits are identified for three different time intervals (today, Holocene, Plio-Pleistocene) evidencing that wind-driven hydrodynamics can be preserved in the geological record. Moreover, a preliminary global survey suggests that numerous modern lakes (remote sensing) and paleo-lakes (bibliographic review) behave as such. We thus coin the term "Wind-driven Water Bodies" (WWB) to refer to those lake systems where sedimentation (erosion, transport, deposition) is dominated by wind-induced hydrodynamics at any depth, as it is the case in the marine realm for shallow seas. Integrating wind forcing in lake models has strong implications for basin analysis (paleoenvironments and paleoclimates restitutions, resources exploration), but also for coastal engineering, wildlife and reservoirs management, or leisure activities.

The relative contribution of processes driving variability in flow, shear, and turbidity over a fringing coral reef: West Maui, Hawaii

Science.gov (United States)

Storlazzi, C.D.; Jaffe, B.E.

2008-01-01

High-frequency measurements of waves, currents and water column properties were made on a fringing coral reef off northwest Maui, Hawaii, for 15 months between 2001 and 2003 to aid in understanding the processes governing flow and turbidity over a range of time scales and their contributions to annual budgets. The summer months were characterized by consistent trade winds and small waves, and under these conditions high-frequency internal bores were commonly observed, there was little net flow or turbidity over the fore reef, and over the reef flat net flow was downwind and turbidity was high. When the trade winds waned or the wind direction deviated from the dominant trade wind orientation, strong alongshore flows occurred into the typically dominant wind direction and lower turbidity was observed across the reef. During the winter, when large storm waves impacted the study area, strong offshore flows and high turbidity occurred on the reef flat and over the fore reef. Over the course of a year, trade wind conditions resulted in the greatest net transport of turbid water due to relatively strong currents, moderate overall turbidity, and their frequent occurrence. Throughout the period of study, near-surface current directions over the fore reef varied on average by more than 41?? from those near the seafloor, and the orientation of the currents over the reef flat differed on average by more than 65?? from those observed over the fore reef. This shear occurred over relatively short vertical (order of meters) and horizontal (order of hundreds of meters) scales, causing material distributed throughout the water column, including the particles in suspension causing the turbidity (e.g. sediment or larvae) and/or dissolved nutrients and contaminants, to be transported in different directions under constant oceanographic and meteorologic forcing.

A review on wind-driven rain research in building science

NARCIS (Netherlands)

Blocken, B.J.E.; Carmeliet, J.E.

2004-01-01

Wind-driven rain (WDR) or driving rain is rain that is given a horizontal velocity component by the wind. WDR research is of importance in a number of research areas including earth sciences, meteorology and building science. Research methods and results are exchangeable between these domains but no

Dynamics of Line-Driven Winds from Disks in Cataclysmic Variables. I. Solution Topology and Wind Geometry

OpenAIRE

Feldmeier, Achim; Shlosman, Isaac

1999-01-01

We analyze the dynamics of 2-D stationary, line-driven winds from accretion disks in cataclysmic variable stars. The driving force is that of line radiation pressure, in the formalism developed by Castor, Abbott & Klein for O stars. Our main assumption is that wind helical streamlines lie on straight cones. We find that the Euler equation for the disk wind has two eigenvalues, the mass loss rate and the flow tilt angle with the disk. Both are calculated self-consistently. The wind is characte...

Radiatively driven relativistic spherical winds under relativistic radiative transfer

Science.gov (United States)

Fukue, J.

2018-05-01

We numerically investigate radiatively driven relativistic spherical winds from the central luminous object with mass M and luminosity L* under Newtonian gravity, special relativity, and relativistic radiative transfer. We solve both the relativistic radiative transfer equation and the relativistic hydrodynamical equations for spherically symmetric flows under the double-iteration processes, to obtain the intensity and velocity fields simultaneously. We found that the momentum-driven winds with scattering are quickly accelerated near the central object to reach the terminal speed. The results of numerical solutions are roughly fitted by a relation of \\dot{m}=0.7(Γ _*-1)\\tau _* β _* β _out^{-2.6}, where \\dot{m} is the mass-loss rate normalized by the critical one, Γ* the central luminosity normalized by the critical one, τ* the typical optical depth, β* the initial flow speed at the central core of radius R*, and βout the terminal speed normalized by the speed of light. This relation is close to the non-relativistic analytical solution, \\dot{m} = 2(Γ _*-1)\\tau _* β _* β _out^{-2}, which can be re-expressed as β _out^2/2 = (Γ _*-1)GM/c^2 R_*. That is, the present solution with small optical depth is similar to that of the radiatively driven free outflow. Furthermore, we found that the normalized luminosity (Eddington parameter) must be larger than unity for the relativistic spherical wind to blow off with intermediate or small optical depth, i.e. Γ _* ≳ \\sqrt{(1+β _out)^3/(1-β _out)}. We briefly investigate and discuss an isothermal wind.

Numerical model for wind-driven circulation in the Bay of Bengal

Digital Repository Service at National Institute of Oceanography (India)

Bahulayan, N.; Varadachari, V.V.R.

Wind-driven circulation in the Bay of Bengal, generated by a southwest wind of constant speed (10 m.sec -1) and direction (225 degrees TN), is presented. A non-linear hydrodynamic model is used for the simulation of circulation. Numerical...

Wind driven saltation: a hitherto overlooked challenge for life on Mars

Science.gov (United States)

Bak, Ebbe; Goul, Michael; Rasmussen, Martin; Moeller, Ralf; Nørnberg, Per; Knak Jensen, Svend; Finster, Kai

2017-04-01

The Martian surface is a hostile environment characterized by low water availability, low atmospheric pressure and high UV and ionizing radiation. Furthermore, wind-driven saltation leads to abrasion of silicates with a production of reactive surface sites and, through triboelectric charging, a release of electrical discharges with a concomitant production of reactive oxygen species. While the effects of low water availability, low pressure and radiation have been extensively studied in relation to the habitability of the Martian surface and the preservation of organic biosignatures, the effects of wind-driven saltation have hitherto been ignored. In this study, we have investigated the effect of exposing bacteria to wind-abraded silicates and directly to wind-driven saltation on Mars in controlled laboratory simulation experiments. Wind-driven saltation was simulated by tumbling mineral samples in a Mars-like atmosphere in sealed quartz ampoules. The effects on bacterial survival and structure were evaluated by colony forming unit counts in combination with scanning electron microscopy, quantitative polymerase chain reaction and life/dead-staining with flow cytometry. The viability of vegetative cells of P. putida, B. subtilis and D. radiodurans in aqueous suspensions was reduced by more than 99% by exposure to abraded basalt, while the viability of B. subtilis endospores was unaffected. B. subtilis mutants lacking different spore components were likewise highly resistant to the exposure to abraded basalt, which indicates that the resistance of spores is not associated with any specific spore component. We found a significant but reduced effect of abraded quartz and we suggest that the stress effect of abraded silicates is induced by a production of reactive oxygen species and hydroxyl radicals produced by Fenton-like reactions in the presence of transition metals. Direct exposure to simulated saltation had a dramatic effect on both D. radiodurans cells and B

The Stability Analysis and New Torque Control Strategy of Direct-Driven PMSG Wind Turbines

OpenAIRE

Jun Liu; Feihang Zhou; Gungyi Wang

2016-01-01

This paper expounds on the direct-driven PMSG wind power system control strategy, and analyses the stability conditions of the system. The direct-driven PMSG wind power system may generate the intense mechanical vibration, when wind speed changes dramatically. This paper proposes a new type of torque control strategy, which increases the system damping effectively, mitigates mechanical vibration of the system, and enhances the stability conditions of the system. The simulation results verify ...

Wind-Driven Wireless Networked System of Mobile Sensors for Mars Exploration

Science.gov (United States)

Davoodi, Faranak; Murphy, Neil

2013-01-01

A revolutionary way is proposed of studying the surface of Mars using a wind-driven network of mobile sensors: GOWON. GOWON would be a scalable, self-powered and autonomous distributed system that could allow in situ mapping of a wide range of environmental phenomena in a much larger portion of the surface of Mars compared to earlier missions. It could improve the possibility of finding rare phenomena such as "blueberries' or bio-signatures and mapping their occurrence, through random wind-driven search. It would explore difficult terrains that were beyond the reach of previous missions, such as regions with very steep slopes and cluttered surfaces. GOWON has a potentially long life span, as individual elements can be added to the array periodically. It could potentially provide a cost-effective solution for mapping wide areas of Martian terrain, enabling leaving a long-lasting sensing and searching infrastructure on the surface of Mars. The system proposed here addresses this opportunity using technology advances in a distributed system of wind-driven sensors, referred to as Moballs.

Drivers of change in estuarine-coastal ecosystems: Discoveries from four decades of study in San Francisco Bay

Science.gov (United States)

Cloern, J.E.; Jassby, A.D.

2012-01-01

Poised at the interface of rivers, ocean, atmosphere and dense human settlement, estuaries are driven by a large array of natural and anthropogenic forces. San Francisco Bay exemplifies the fast-paced change occurring in many of the world's estuaries, bays and inland seas in response to these diverse forces. We use observations from this particularly well-studied estuary to illustrate responses to six drivers that are common agents of change where land and sea meet: water consumption and diversion; human modification of sediment supply; introduction of non-native species; sewage input; environmental policy; and climate shifts. In San Francisco Bay, responses to these drivers include, respectively, shifts in the timing and extent of freshwater inflow and salinity intrusion; decreasing turbidity; restructuring of plankton communities; nutrient enrichment; elimination of hypoxia and reduced metal contamination of biota; and food web changes that decrease resistance of the estuary to nutrient pollution. Detection of these changes and discovery of their causes through environmental monitoring have been essential for establishing and measuring outcomes of environmental policies that aim to maintain high water quality and sustain services provided by estuarine-coastal ecosystems. The wide range of variability time scales and the multiplicity of interacting drivers place heavy demands on estuarine monitoring programs. But the San Francisco Bay case study illustrates why the imperative for monitoring has never been greater.

Drivers of change in estuarine-coastal ecosystems: Discoveries from four decades of study in San Francisco Bay

Science.gov (United States)

Cloern, James E.; Jassby, Alan D.

2012-12-01

Poised at the interface of rivers, ocean, atmosphere and dense human settlement, estuaries are driven by a large array of natural and anthropogenic forces. San Francisco Bay exemplifies the fast-paced change occurring in many of the world's estuaries, bays, and inland seas in response to these diverse forces. We use observations from this particularly well-studied estuary to illustrate responses to six drivers that are common agents of change where land and sea meet: water consumption and diversion, human modification of sediment supply, introduction of nonnative species, sewage input, environmental policy, and climate shifts. In San Francisco Bay, responses to these drivers include, respectively, shifts in the timing and extent of freshwater inflow and salinity intrusion, decreasing turbidity, restructuring of plankton communities, nutrient enrichment, elimination of hypoxia and reduced metal contamination of biota, and food web changes that decrease resistance of the estuary to nutrient pollution. Detection of these changes and discovery of their causes through environmental monitoring have been essential for establishing and measuring outcomes of environmental policies that aim to maintain high water quality and sustain services provided by estuarine-coastal ecosystems. The many time scales of variability and the multiplicity of interacting drivers place heavy demands on estuarine monitoring programs, but the San Francisco Bay case study illustrates why the imperative for monitoring has never been greater.

Mid-depth temperature maximum in an estuarine lake

Science.gov (United States)

Stepanenko, V. M.; Repina, I. A.; Artamonov, A. Yu; Gorin, S. L.; Lykossov, V. N.; Kulyamin, D. V.

2018-03-01

The mid-depth temperature maximum (TeM) was measured in an estuarine Bol’shoi Vilyui Lake (Kamchatka peninsula, Russia) in summer 2015. We applied 1D k-ɛ model LAKE to the case, and found it successfully simulating the phenomenon. We argue that the main prerequisite for mid-depth TeM development is a salinity increase below the freshwater mixed layer, sharp enough in order to increase the temperature with depth not to cause convective mixing and double diffusion there. Given that this condition is satisfied, the TeM magnitude is controlled by physical factors which we identified as: radiation absorption below the mixed layer, mixed-layer temperature dynamics, vertical heat conduction and water-sediments heat exchange. In addition to these, we formulate the mechanism of temperature maximum ‘pumping’, resulting from the phase shift between diurnal cycles of mixed-layer depth and temperature maximum magnitude. Based on the LAKE model results we quantify the contribution of the above listed mechanisms and find their individual significance highly sensitive to water turbidity. Relying on physical mechanisms identified we define environmental conditions favouring the summertime TeM development in salinity-stratified lakes as: small-mixed layer depth (roughly, ~wind and cloudless weather. We exemplify the effect of mixed-layer depth on TeM by a set of selected lakes.

Tidal variations of flow convergence, shear, and stratification at the Rio de la Plata estuary turbidity front

Science.gov (United States)

FramiñAn, Mariana B.; Valle-Levinson, Arnoldo; Sepúlveda, HéCtor H.; Brown, Otis B.

2008-08-01

Intratidal variability of density and velocity fields is investigated at the turbidity front of the Río de la Plata Estuary, South America. Current velocity and temperature-salinity profiles collected in August 1999 along a repeated transect crossing the front are analyzed. Horizontal and vertical gradients, stability of the front, convergence zones, and transverse flow associated to the frontal boundary are described. Strong horizontal convergence of the across-front velocity and build up of along-front velocity shear were observed at the front. In the proximity of the front, enhanced transverse (or along-front) flow created jet-like structures at the surface and near the bottom flowing in opposite directions. These structures persisted throughout the tidal cycle and were advected upstream (downstream) by the flood (ebb) current through a distance of ˜10 km. During peak flood, the upper layer flow reversed from its predominant downstream direction and upstreamflow occupied the entire water column; outside the peak flood, two-layer estuarine circulation dominated. Changes in density field were observed in response to tidal straining, tidal advection, and wind-induced mixing, but stratification remained throughout the tidal cycle. This work demonstrates the large spatial variability of the velocity field at the turbidity front; it provides evidence of enhanced transverse circulation along the frontal boundary; and reveals the importance of advective and frictional intratidal processes in the dynamics of the central part of the estuary.

Investigation of turbidity effect on exergetic performance of solar ponds

International Nuclear Information System (INIS)

Atiz, Ayhan; Bozkurt, Ismail; Karakilcik, Mehmet; Dincer, Ibrahim

2014-01-01

Highlights: • A comprehensive experimental work on a turbidity of the solar pond. • Percentage transmission evaluation of the turbid and clean salty water of the zones. • Exergy analysis of the inner zones for turbid and clean salty water. • Turbidity effect on exergy efficiencies of the solar pond. • The thermal performance assessment by comparing the exergetic efficiencies of the solar pond. - Abstract: The present paper undertakes a study on the exergetic performance assessment of a solar pond and experimental investigation of turbidity effect on the system performance. There are various types of solar energy applications including solar ponds. One of significant parameters to consider in the assessment of solar pond performance is turbidity which is caused by dirty over time (e.g., insects, leaf, dust and wind bringing parts fall down). Thus, the turbidity in the salty water decreases solar energy transmission through the zones. In this study, the samples are taken from the three zones of the solar pond and analyzed using a spectrometer for three months. The transmission aspects of the solar pond are investigated under calm and turbidity currents to help distinguish the efficiencies. Furthermore, the maximum exergy efficiencies are found to be 28.40% for the calm case and 22.27% with turbidity effects for the month of August, respectively. As a result, it is confirmed that the solar pond performance is greatly affected by the turbidity effect

Analysis of wind driven self-excited induction generator supplying isolated DC loads

Directory of Open Access Journals (Sweden)

Khaled S. Sakkoury

2017-05-01

Full Text Available This paper presents the analysis, modelling and simulation of wind-driven self-excited induction generator (SEIG. The three-phase SEIG is driven by a variable-speed prime mover to represent a wind turbine. Also, the paper investigates the dynamic performance of the SEIG during start-up, increasing or decreasing the load or rotor speed. The value of the excitation capacitance required for the SEIG is calculated to give suitable saturation level to assure self-excitation and to avoid heavy saturation levels. Matching of the maximum power available from the wind turbine is performed through varying the load value. The effect of AC–DC power conversion on the generator is investigated. The system simulation is carried out using MATLAB/SIMULINK toolbox program.

Estuarine morphodynamic adaptation to sediment supply and human activities : A case study of turbidity maximum

NARCIS (Netherlands)

Zhu, C.; Guo, L; Tian, B.; He, Q; Wang, Zhengbing

2017-01-01

Estuarine morphodynamics undergo significant changes due to declined sediment supply from river, rising sea-level, and human interferences (Syvitski and Saito, 2007; Syvitski et al., 2009). The Yangtze Estuary is such a case whose decadal morphodynamic evolution was broadly examined. It was

Assisted stellar suicide: the wind-driven evolution of the recurrent nova T Pyxidis

Science.gov (United States)

Knigge, Ch.; King, A. R.; Patterson, J.

2000-12-01

We show that the extremely high luminosity of the short-period recurrent nova T Pyx in quiescence can be understood if this system is a wind-driven supersoft x-ray source (SSS). In this scenario, a strong, radiation-induced wind is excited from the secondary star and accelerates the binary evolution. The accretion rate is therefore much higher than in an ordinary cataclysmic binary at the same orbital period, as is the luminosity of the white dwarf primary. In the steady state, the enhanced luminosity is just sufficient to maintain the wind from the secondary. The accretion rate and luminosity predicted by the wind-driven model for T Pyx are in good agreement with the observational evidence. X-ray observations with Chandra or XMM may be able to confirm T Pyx's status as a SSS. T Pyx's lifetime in the wind-driven state is on the order of a million years. Its ultimate fate is not certain, but the system may very well end up destroying itself, either via the complete evaporation of the secondary star, or in a Type Ia supernova if the white dwarf reaches the Chandrasekhar limit. Thus either the primary, the secondary, or both may currently be committing assisted stellar suicide.

Evolution of sediment plumes in the Chesapeake bay and implications of climate variability.

Science.gov (United States)

Zheng, Guangming; DiGiacomo, Paul M; Kaushal, Sujay S; Yuen-Murphy, Marilyn A; Duan, Shuiwang

2015-06-02

Fluvial sediment transport impacts fisheries, marine ecosystems, and human health. In the upper Chesapeake Bay, river-induced sediment plumes are generally known as either a monotonic spatial shape or a turbidity maximum. Little is known about plume evolution in response to variation in streamflow and extreme discharge of sediment. Here we propose a typology of sediment plumes in the upper Chesapeake Bay using a 17 year time series of satellite-derived suspended sediment concentration. On the basis of estimated fluvial and wind contributions, we define an intermittent/wind-dominated type and a continuous type, the latter of which is further divided into four subtypes based on spatial features of plumes, which we refer to as Injection, Transport, Temporary Turbidity-Maximum, and Persistent Turbidity-Maximum. The four continuous types exhibit a consistent sequence of evolution within 1 week to 1 month following flood events. We also identify a "shift" in typology with increased frequency of Turbidity-Maximum types before and after Hurricane Ivan (2004), which implies that extreme events have longer-lasting effects upon estuarine suspended sediment than previously considered. These results can serve as a diagnostic tool to better predict distribution and impacts of estuarine suspended sediment in response to changes in climate and land use.

Power quality issues of 3MW direct-driven PMSG wind turbine

OpenAIRE

Ahmed, IA; Zobaa, AF; Taylor, GA

2015-01-01

This paper presents power quality issues of a grid connected wind generation system with a MW-class direct-driven permanent magnet synchronous generator (PMSG). A variable speed wind turbine model was simulated and developed with the simulation tool of PSCAD/EMTDC. The model includes a wind turbine with one mass-model drive train model, a PMSG model and a full-scale voltage source back to back PWM converter. The converter controller model is employed in the dq-synchronous rotating reference f...

The dependence of cosmic ray-driven galactic winds on halo mass

Science.gov (United States)

Jacob, Svenja; Pakmor, Rüdiger; Simpson, Christine M.; Springel, Volker; Pfrommer, Christoph

2018-03-01

Galactic winds regulate star formation in disc galaxies and help to enrich the circum-galactic medium. They are therefore crucial for galaxy formation, but their driving mechanism is still poorly understood. Recent studies have demonstrated that cosmic rays (CRs) can drive outflows if active CR transport is taken into account. Using hydrodynamical simulations of isolated galaxies with virial masses between 1010 and 1013 M⊙, we study how the properties of CR-driven winds depend on halo mass. CRs are treated in a two-fluid approximation and their transport is modelled through isotropic or anisotropic diffusion. We find that CRs are only able to drive mass-loaded winds beyond the virial radius in haloes with masses below 1012 M⊙. For our lowest examined halo mass, the wind is roughly spherical and has velocities of ˜20 km s-1. With increasing halo mass, the wind becomes biconical and can reach 10 times higher velocities. The mass loading factor drops rapidly with virial mass, a dependence that approximately follows a power law with a slope between -1 and -2. This scaling is slightly steeper than observational inferences, and also steeper than commonly used prescriptions for wind feedback in cosmological simulations. The slope is quite robust to variations of the CR injection efficiency or the CR diffusion coefficient. In contrast to the mass loading, the energy loading shows no significant dependence on halo mass. While these scalings are close to successful heuristic models of wind feedback, the CR-driven winds in our present models are not yet powerful enough to fully account for the required feedback strength.

New Solutions to Line-Driven Winds of Hot Massive Stars

Science.gov (United States)

Gormaz-Matamala, Alex C.; Curé, Michel; Cidale, Lydia; Venero, Roberto

2017-11-01

In the frame of radiation driven wind theory (Castor et al.1975), we present self-consistent hydrodynamical solutions to the line-force parameters (k, α, δ) under LTE conditions. Hydrodynamic models are provided by HydWind (Curé 2004). We evaluate these results with those ones previously found in literature, focusing in different regions of the optical depth to be used to perform the calculations. The values for mass-loss rate and terminal velocity obtained from our calculations are also presented. We also examine the line-force parameters for the case when large changes in ionization throughout the wind occurs (δ-slow solutions, Curé et al.2011).

Coastal and estuarine resources of Bangladesh: management and conservation issues

Directory of Open Access Journals (Sweden)

Abu Hena M. Kamal

2009-07-01

Full Text Available The coastal area of Bangladesh includes a number of bays into which different types of rivers empty, creating an estuarine ecosystem adjacent to the shore. The main estuarine systems are Brahmaputra-Megna (Gangetic delta, Karnaphuly, Matamuhuri, Bakkhali and Naf rivers, which are comprised of mangroves, salt marshes, seagrass, seaweeds, fisheries, coastal birds, animals, coral reefs, deltas, salt beds, minerals and sand dunes. The estuarine environment, which serves as feeding, breeding and nursery grounds for a variety of animals, varies according to the volume of discharge of the river and tidal range. It is highly productive in terms of nutrient input from different sources that promotes other living resources in the estuaries. Drought conditions exist during the winter months, i.e. November to February, and effective rainfall is confined to the monsoon period, i.e. May to June. Changes in salinity and turbidity depend on annual rainfall. The colour of most estuarine waters is tea brown or brown due to heavy outflows during the monsoon. The tidal mixing and riverine discharge governs the distribution of the hydrological parameters. The pH of these waters is reported to be slightly alkaline (>7.66 and dissolved oxygen (<6.0 mg/l shows an inverse relationship to temperature. Studies of plankton have indicated two periods of maximum abundance, i.e. February-March and August-September. The abundance of fish and shrimp larvae varies in number and composition with season. Many marine and freshwater species are available in various types of coastal brackish water, which depend on monsoonal activities and local environmental conditions.

Studies on battery storage requirement of PV fed wind-driven induction generators

International Nuclear Information System (INIS)

Rajan Singaravel, M.M.; Arul Daniel, S.

2013-01-01

Highlights: ► Sizing of battery storage for PV fed wind-driven IG system is taken up. ► Battery storage is also used to supply reactive power for wind-driven IG. ► Computation of LPSP by incorporating uncertainties of irradiation and wind speed. ► Sizing of hybrid power system components to ensure zero LPSP. ► Calculated storage size satisfied the constraints and improves battery life. - Abstract: Hybrid stand-alone renewable energy systems based on wind–solar resources are considered to be economically better and reliable than stand-alone systems with a single source. An isolated hybrid wind–solar system has been considered in this work, where the storage (battery bank) is necessary to supply the required reactive power for a wind-driven induction generator (IG) during the absence of power from a photovoltaic (PV) array. In such a scheme, to ensure zero Loss of Power Supply Probability (LPSP) and to improve battery bank life, a sizing procedure has been proposed with the incorporation of uncertainties in wind-speed and solar-irradiation level at the site of erection of the plant. Based on the proposed procedure, the size of hybrid power system components and storage capacity are determined. Storage capacity has been calculated for two different requirements. The first requirement of storage capacity is common to any hybrid scheme, which is; to supply both real and reactive power in the absence of wind and solar sources. The second requirement is to supply reactive power alone for the IG during the absence of photovoltaic power, which is unique to the hybrid scheme considered in this work. Storage capacity calculations for different conditions using the proposed approach, satisfies the constraints of maintaining zero LPSP and also improved cycle life of the battery bank

Short-term forecasting of turbidity in trunk main networks.

Science.gov (United States)

Meyers, Gregory; Kapelan, Zoran; Keedwell, Edward

2017-11-01

Water discolouration is an increasingly important and expensive issue due to rising customer expectations, tighter regulatory demands and ageing Water Distribution Systems (WDSs) in the UK and abroad. This paper presents a new turbidity forecasting methodology capable of aiding operational staff and enabling proactive management strategies. The turbidity forecasting methodology developed here is completely data-driven and does not require hydraulic or water quality network model that is expensive to build and maintain. The methodology is tested and verified on a real trunk main network with observed turbidity measurement data. Results obtained show that the methodology can detect if discolouration material is mobilised, estimate if sufficient turbidity will be generated to exceed a preselected threshold and approximate how long the material will take to reach the downstream meter. Classification based forecasts of turbidity can be reliably made up to 5 h ahead although at the expense of increased false alarm rates. The methodology presented here could be used as an early warning system that can enable a multitude of cost beneficial proactive management strategies to be implemented as an alternative to expensive trunk mains cleaning programs. Copyright © 2017 Elsevier Ltd. All rights reserved.

Mechanisms of Complete Turbulence Suppression in Turbidity Currents Driven by Mono-Disperse and Bi-Disperse Suspensions of Sediment

Directory of Open Access Journals (Sweden)

Mrugesh S. Shringarpure

2014-09-01

appears to have a logarithmic dependence on Reτ (Cantero et al. 2012. DNS of turbidity currents driven by bi-disperse suspension of sediments is also carried out and compared with the results of mono-disperse suspensions.

Turbine sound may influence the metamorphosis behaviour of estuarine crab megalopae.

Science.gov (United States)

Pine, Matthew K; Jeffs, Andrew G; Radford, Craig A

2012-01-01

It is now widely accepted that a shift towards renewable energy production is needed in order to avoid further anthropogenically induced climate change. The ocean provides a largely untapped source of renewable energy. As a result, harvesting electrical power from the wind and tides has sparked immense government and commercial interest but with relatively little detailed understanding of the potential environmental impacts. This study investigated how the sound emitted from an underwater tidal turbine and an offshore wind turbine would influence the settlement and metamorphosis of the pelagic larvae of estuarine brachyuran crabs which are ubiquitous in most coastal habitats. In a laboratory experiment the median time to metamorphosis (TTM) for the megalopae of the crabs Austrohelice crassa and Hemigrapsus crenulatus was significantly increased by at least 18 h when exposed to either tidal turbine or sea-based wind turbine sound, compared to silent control treatments. Contrastingly, when either species were subjected to natural habitat sound, observed median TTM decreased by approximately 21-31% compared to silent control treatments, 38-47% compared to tidal turbine sound treatments, and 46-60% compared to wind turbine sound treatments. A lack of difference in median TTM in A. crassa between two different source levels of tidal turbine sound suggests the frequency composition of turbine sound is more relevant in explaining such responses rather than sound intensity. These results show that estuarine mudflat sound mediates natural metamorphosis behaviour in two common species of estuarine crabs, and that exposure to continuous turbine sound interferes with this natural process. These results raise concerns about the potential ecological impacts of sound generated by renewable energy generation systems placed in the nearshore environment.

Turbine sound may influence the metamorphosis behaviour of estuarine crab megalopae.

Directory of Open Access Journals (Sweden)

Matthew K Pine

Full Text Available It is now widely accepted that a shift towards renewable energy production is needed in order to avoid further anthropogenically induced climate change. The ocean provides a largely untapped source of renewable energy. As a result, harvesting electrical power from the wind and tides has sparked immense government and commercial interest but with relatively little detailed understanding of the potential environmental impacts. This study investigated how the sound emitted from an underwater tidal turbine and an offshore wind turbine would influence the settlement and metamorphosis of the pelagic larvae of estuarine brachyuran crabs which are ubiquitous in most coastal habitats. In a laboratory experiment the median time to metamorphosis (TTM for the megalopae of the crabs Austrohelice crassa and Hemigrapsus crenulatus was significantly increased by at least 18 h when exposed to either tidal turbine or sea-based wind turbine sound, compared to silent control treatments. Contrastingly, when either species were subjected to natural habitat sound, observed median TTM decreased by approximately 21-31% compared to silent control treatments, 38-47% compared to tidal turbine sound treatments, and 46-60% compared to wind turbine sound treatments. A lack of difference in median TTM in A. crassa between two different source levels of tidal turbine sound suggests the frequency composition of turbine sound is more relevant in explaining such responses rather than sound intensity. These results show that estuarine mudflat sound mediates natural metamorphosis behaviour in two common species of estuarine crabs, and that exposure to continuous turbine sound interferes with this natural process. These results raise concerns about the potential ecological impacts of sound generated by renewable energy generation systems placed in the nearshore environment.

Kinetic instabilities in the solar wind driven by temperature anisotropies

Science.gov (United States)

Yoon, Peter H.

2017-12-01

The present paper comprises a review of kinetic instabilities that may be operative in the solar wind, and how they influence the dynamics thereof. The review is limited to collective plasma instabilities driven by the temperature anisotropies. To limit the scope even further, the discussion is restricted to the temperature anisotropy-driven instabilities within the model of bi-Maxwellian plasma velocity distribution function. The effects of multiple particle species or the influence of field-aligned drift will not be included. The field-aligned drift or beam is particularly prominent for the solar wind electrons, and thus ignoring its effect leaves out a vast portion of important physics. Nevertheless, for the sake of limiting the scope, this effect will not be discussed. The exposition is within the context of linear and quasilinear Vlasov kinetic theories. The discussion does not cover either computer simulations or data analyses of observations, in any systematic manner, although references will be made to published works pertaining to these methods. The scientific rationale for the present analysis is that the anisotropic temperatures associated with charged particles are pervasively detected in the solar wind, and it is one of the key contemporary scientific research topics to correctly characterize how such anisotropies are generated, maintained, and regulated in the solar wind. The present article aims to provide an up-to-date theoretical development on this research topic, largely based on the author's own work.

Ecology of Vibrio vulnificus in estuarine waters of eastern North Carolina.

Science.gov (United States)

Pfeffer, Courtney S; Hite, M Frances; Oliver, James D

2003-06-01

While several studies on the ecology of Vibrio vulnificus in Gulf Coast environments have been reported, there is little information on the distribution of this pathogen in East Coast waters. Thus, we conducted a multiyear study on the ecology of V. vulnificus in estuarine waters of the eastern United States, employing extensive multiple regression analyses to reveal the major environmental factors controlling the presence of this pathogen, and of Vibrio spp., in these environments. Monthly field samplings were conducted between July 2000 and April 2002 at six different estuarine sites along the eastern coast of North Carolina. At each site, water samples were taken and nine physicochemical parameters were measured. V. vulnificus isolates, along with estuarine bacteria, Vibrio spp., Escherichia coli organisms, and total coliforms, were enumerated in samples from each site by using selective media. During the last 6 months of the study, sediment samples were also analyzed for the presence of vibrios, including V. vulnificus. Isolates were confirmed as V. vulnificus by using hemolysin gene PCR or colony hybridization. V. vulnificus was isolated only when water temperatures were between 15 and 27 degrees C, and its presence correlated with water temperature and dissolved oxygen and vibrio levels. Levels of V. vulnificus in sediments were low, and no evidence for an overwintering in this environment was found. Multiple regression analysis indicated that vibrio levels were controlled primarily by temperature, turbidity, and levels of dissolved oxygen, estuarine bacteria, and coliforms. Water temperature accounted for most of the variability in the concentrations of both V. vulnificus (47%) and Vibrio spp. (48%).

Changes in phytoplankton composition in response to tides, wind-induced mixing conditions, and freshwater outflows in an urbanised estuarine complex.

Science.gov (United States)

Moser, G A O; Ciotti, A M; Giannini, M F C; Tonini, R T; Harari, J

2012-02-01

Recent reports have shown an increase in potentially harmful phytoplankton in Santos bay (Southeastern Brazilian Coast), located in a highly urbanised estuarine complex. Prediction of blooms is, thus, essential but the phytoplankton community structure in very dynamic regions is difficult to determine. In the present work, we discriminate bloom forming microphytoplankton dominance and their relationship to physical and meteorological variables to look for patterns observed in different tides and seasons. Comparing 8 distinct situations, we found five scenarios of dominance that could be related to winds, tides and rainfall: i) Surfers, diatoms occurring during high surf zone energies; ii) Sinkers, represented by larger celled diatoms during spring tide, after periods of high precipitation rates; iii) Opportunistic mixers, composed of chain forming diatoms with small or elongate cells occurring during neap tides; iv) Local mixers, microplanktonic diatoms and dinoflagellates which occurred throughout the 298 sampling stations; and v) Mixotrophic dinoflagellates, after intense estuarine discharges. Results suggest alterations in the temporal patterns for some bloom-forming species, while others appeared in abundances above safe limits for public health. This approach can also illustrate possible impacts of changes in freshwater discharge in highly urbanised estuaries.

Winds from accretion disks driven by the radiation and magnetocentrifugal force

OpenAIRE

Proga, D.

2000-01-01

We study the 2-D, time-dependent hydrodynamics of radiation-driven winds from luminous accretion disks threaded by a strong, large-scale, ordered magnetic field. The radiation force is due to spectral lines and is calculated using a generalized multidimensional formulation of the Sobolev approximation. The effects of the magnetic field are approximated by adding a force that emulates a magnetocentrifugal force. Our approach allows us to calculate disk winds when the magnetic field controls th...

Towards a long-term chlorophyll-a data record in a turbid estuary using MODIS observations

Science.gov (United States)

Le, Chengfeng; Hu, Chuanmin; English, David; Cannizzaro, Jennifer; Chen, Zhiqiang; Feng, Lian; Boler, Richard; Kovach, Charles

2013-02-01

Despite recent advances in using satellite data for continuous monitoring of estuarine water quality parameters such as turbidity and water clarity, estimating chlorophyll-a concentrations (Chla) has remained problematic due to the optical complexity of estuarine waters and imperfect atmospheric correction. This poses a significant challenge to the community as synoptic and frequent Chla “measurements” from satellites are in high demand by various government agencies and environmental groups to help make management decisions. Here, using 10 years of in situ and Moderate Resolution Imaging Spectroradiometer (MODIS) measurements from a moderately sized, turbid estuary, Tampa Bay (Florida, USA), we developed and validated a new algorithm specifically designed for retrieving Chla from MODIS data. The algorithm takes the red-to-green remote-sensing reflectance (Rrs(λ)) band ratio of [Rrs(667) + Rrs(678)]/[Rrs(531) + Rrs(547)] as the independent variable, and estimates Chla through the non-linear regression function: Ln(Chla) = 1.91Ln(x) + 3.40 (R2 = 0.87, N = 97, p < 0.01, 1.5 < Chla < 80 mg m-3) where ‘x' is the band ratio. Validation of the algorithm using two independent datasets collected by different groups and near-concurrent MODIS measurements showed robust algorithm performance for Chla within this range, with mean relative errors of 25.8% and 41.7% for the two datasets. Time-series analyses at representative stations using both in situ and MODIS Chla also showed general agreement, with instances of noticeable discrepancy attributed to different measurement frequencies. The algorithm was implemented to establish a 10-year Chla data record for Tampa Bay in order to serve as a baseline for monitoring future phytoplankton bloom events. The 10-year Chla data record showed substantial variability in both space and time, with generally higher Chla observed during the wet season and in upper bay segments, and Chla minima observed in all bay segments during May

Spatial distribution of suspended particulate matter in the Mandovi and Zuari estuaries: inferences on the estuarine turbidity maximum

Digital Repository Service at National Institute of Oceanography (India)

Suja, S.; Kessarkar, P.M.; Shynu, R.; Rao, V.P.; Fernandes, L.L.

to tidal and wind-driven waves and currents. Our results corroborate the findings of Kes- sarkar et al.10,16 that high ETM is associ- ated with high salinity at the sea end. The vertical profiles of SPM suggest ex- tension of this ETM up to 2 m depth... instantaneously forming a high-temperature mineral phase (fayalite) along with a quenched glassy matrix. Studies on ancient slags worldwide7–10 have shown that the proportions of phos- phorus are in the range 0.05–0.5 wt%, with levels up to 1.0 wt...

WIND-DRIVEN ACCRETION IN TRANSITIONAL PROTOSTELLAR DISKS

Energy Technology Data Exchange (ETDEWEB)

Wang, Lile; Goodman, Jeremy J. [Princeton University Observatory, Princeton, NJ 08544 (United States)

2017-01-20

Transitional protostellar disks have inner cavities that are heavily depleted in dust and gas, yet most of them show signs of ongoing accretion, often at rates comparable to full disks. We show that recent constraints on the gas surface density in a few well-studied disk cavities suggest that the accretion speed is at least transsonic. We propose that this is the natural result of accretion driven by magnetized winds. Typical physical conditions of the gas inside these cavities are estimated for plausible X-ray and FUV radiation fields. The gas near the midplane is molecular and predominantly neutral, with a dimensionless ambipolar parameter in the right general range for wind solutions of the type developed by Königl, Wardle, and others. That is to say, the density of ions and electrons is sufficient for moderately good coupling to the magnetic field, but it is not so good that the magnetic flux needs to be dragged inward by the accreting neutrals.

Instabilities of line-driven stellar winds. V. Effect of an optically thick continuum

International Nuclear Information System (INIS)

Owocki, S.P.; Rybicki, G.B.

1991-01-01

Earlier analyses of the linear instability of line-driven stellar winds are extended to the case, relevant to Wolf-Rayet stars, in which the continuum remains optically thick well above the sonic point. It is found that an optically thick flow driven by pure scattering lines is stabilized by the drag effect of the diffuse, scattered radiation. However, even a relatively small photon destruction probability can cause a flow with continuum optical thickness much greater than 1 to remain unstable, with a given growth rate. The implications of these results for the variability characteristics of winds from Wolf-Rayet stars are briefly discussed. 16 refs

Wind-driven angular momentum loss in binary systems. I - Ballistic case

Science.gov (United States)

Brookshaw, Leigh; Tavani, Marco

1993-01-01

We study numerically the average loss of specific angular momentum from binary systems due to mass outflow from one of the two stars for a variety of initial injection geometries and wind velocities. We present results of ballistic calculations in three dimensions for initial mass ratios q of the mass-losing star to primary star in the range q between 10 exp -5 and 10. We consider injection surfaces close to the Roche lobe equipotential surface of the mass-losing star, and also cases with the mass-losing star underfilling its Roche lobe. We obtain that the orbital period is expected to have a negative time derivative for wind-driven secular evolution of binaries with q greater than about 3 and with the mass-losing star near filling its Roche lobe. We also study the effect of the presence of an absorbing surface approximating an accretion disk on the average final value of the specific angular momentum loss. We find that the effect of an accretion disk is to increase the wind-driven angular momentum loss. Our results are relevant for evolutionary models of high-mass binaries and low-mass X-ray binaries.

Dynamics of coarse particulate matter in the turbidity maximum zone of the Gironde Estuary

Science.gov (United States)

Fuentes-Cid, Ana; Etcheber, Henri; Schmidt, Sabine; Abril, Gwenaël; De-Oliveira, Eric; Lepage, Mario; Sottolichio, Aldo

2014-01-01

There is a lack of studies devoted to coarse particulate matter (CPM) in estuaries, although this fraction can disturb activities that filter large volumes of water, such as industrial or fishery activities. In the macrotidal and highly-turbid Gironde Estuary, a monthly sampling of CPM was performed in 2011 and 2013 at two stations in the Turbidity Maximum Zone (TMZ) to understand its seasonal, tidal and hydrological dynamics. Regardless of the season and station, low quantities of CPM (few g m-3) were observed in comparison with suspended particulate matter (several 103 g m-3). The highest concentrations were consistently recorded in bottom waters and at the upstream station. Whereas there is no clear link between the CPM present in the column water and spring or neap tides, an increase in the CPM size has been identified at the two stations after a flood event, fact potentially critical regarding filtering functioning of estuarine activities.

Turbine Sound May Influence the Metamorphosis Behaviour of Estuarine Crab Megalopae

Science.gov (United States)

Pine, Matthew K.; Jeffs, Andrew G.; Radford, Craig A.

2012-01-01

It is now widely accepted that a shift towards renewable energy production is needed in order to avoid further anthropogenically induced climate change. The ocean provides a largely untapped source of renewable energy. As a result, harvesting electrical power from the wind and tides has sparked immense government and commercial interest but with relatively little detailed understanding of the potential environmental impacts. This study investigated how the sound emitted from an underwater tidal turbine and an offshore wind turbine would influence the settlement and metamorphosis of the pelagic larvae of estuarine brachyuran crabs which are ubiquitous in most coastal habitats. In a laboratory experiment the median time to metamorphosis (TTM) for the megalopae of the crabs Austrohelice crassa and Hemigrapsus crenulatus was significantly increased by at least 18 h when exposed to either tidal turbine or sea-based wind turbine sound, compared to silent control treatments. Contrastingly, when either species were subjected to natural habitat sound, observed median TTM decreased by approximately 21–31% compared to silent control treatments, 38–47% compared to tidal turbine sound treatments, and 46–60% compared to wind turbine sound treatments. A lack of difference in median TTM in A. crassa between two different source levels of tidal turbine sound suggests the frequency composition of turbine sound is more relevant in explaining such responses rather than sound intensity. These results show that estuarine mudflat sound mediates natural metamorphosis behaviour in two common species of estuarine crabs, and that exposure to continuous turbine sound interferes with this natural process. These results raise concerns about the potential ecological impacts of sound generated by renewable energy generation systems placed in the nearshore environment. PMID:23240063

The thermal structure of a wind-driven Reynolds ridge

Energy Technology Data Exchange (ETDEWEB)

Phongikaroon, Supathorn; Peter Judd, K.; Smith, Geoffrey B.; Handler, Robert A. [Remote Sensing Division, Naval Research Laboratory, 20375, Washington, DC (United States)

2004-08-01

In this study, we investigate the nature of a Reynolds ridge formed by wind shear. We have simultaneously imaged the water surface, with a deposit of a monolayer of the surfactant, oleyl alcohol, subject to different wind shears, by using a high-resolution infrared (IR) detector and a high-speed (HS) digital camera. The results reveal that the regions around the wind-driven Reynolds ridge, which have subtle manifestations in visual imagery, possess surprisingly complex hydrodynamical and thermal structures when observed in the infrared. The IR measurements reveal a warm, clean region upstream of the ridge, which is composed of the so called fishscale structures observed in earlier investigations. The region downstream of the ridge is composed of colder fluid which forms two counter-rotating cells. A region of intermediate temperature, which we call the mixing (wake) region, forms immediately downstream of the ridge near the channel centerline. By measuring the velocity of the advected fishscales, we have determined a surface drift speed of about 2% of the wind speed. The spanwise length-scale of the structures has also been used to estimate the wind shear. In addition, a comparison of IR and visual imagery shows that the thermal field is a very sensitive indicator of the exact position of the ridge itself. (orig.)

Wind driven erosion and the effects of particulate electrification

Science.gov (United States)

Merrison, J. P.; Bak, E.; Finster, K.; Gunnlaugsson, H. P.; Holstein-Rathlou, C.; Knak Jensen, S.; Nørnberg, P.; Rasmussen, K. R.

2012-09-01

Several related aspects of Aeolian activity are presently being studied in the laboratory, the most recent advances in this field will be presented. These include simulating wind driven erosion in the laboratory, quantifying erosion rates and the study of mineral change due to mechanical activation. Also advances in our understanding of the electrification of sand/dust particles is being made and how this phenomenon affects their behavior.

Conventional and novel control designs for direct driven PMSG wind turbines

Energy Technology Data Exchange (ETDEWEB)

Li, Shuhui; Haskew, Timothy A.; Xu, Ling [Department of Electrical and Computer Engineering, The University of Alabama, 317 Houser Hall, Tuscaloosa, AL 35487 (United States)

2010-03-15

With the advance of power electronic technology, direct driven permanent magnet synchronous generators (PMSG) have increasingly drawn interests to wind turbine manufactures. This paper studies and compares conventional and a novel control designs for a direct driven PMSG wind turbine. The paper presents transient and steady-state models of a PMSG system in a d-q reference frame. Then, general PMSG characteristics are investigated in the rotor-flux-oriented frame. A shortage of conventional control mechanisms is studied analytically and through computer simulation. A novel direct-current based d-q vector control technique is proposed by integrating fuzzy, adaptive and traditional PID control technologies in an optimal control configuration. Comparison study demonstrates that the proposed control approach, having superior performance in various aspects, is effective not only in achieving desired PMSG control objectives but also in improving the optimal performance of the overall system. (author)

Assessments at multiple levels of biological organization allow for an integrative determination of physiological tolerances to turbidity in an endangered fish species.

Science.gov (United States)

Hasenbein, Matthias; Fangue, Nann A; Geist, Juergen; Komoroske, Lisa M; Truong, Jennifer; McPherson, Rina; Connon, Richard E

2016-01-01

Turbidity can influence trophic levels by altering species composition and can potentially affect fish feeding strategies and predator-prey interactions. The estuarine turbidity maximum, described as an area of increased suspended particles, phytoplankton and zooplankton, generally represents a zone with higher turbidity and enhanced food sources important for successful feeding and growth in many fish species. The delta smelt (Hypomesus transpacificus) is an endangered, pelagic fish species endemic to the San Francisco Estuary and Sacramento-San Joaquin River Delta, USA, where it is associated with turbid waters. Turbidity is known to play an important role for the completion of the species' life cycle; however, turbidity ranges in the Delta are broad, and specific requirements for this fish species are still unknown. To evaluate turbidity requirements for early life stages, late-larval delta smelt were maintained at environmentally relevant turbidity levels ranging from 5 to 250 nephelometric turbidity units (NTU) for 24 h, after which a combination of physiological endpoints (molecular biomarkers and cortisol), behavioural indices (feeding) and whole-organism measures (survival) were determined. All endpoints delivered consistent results and identified turbidities between 25 and 80 NTU as preferential. Delta smelt survival rates were highest between 12 and 80 NTU and feeding rates were highest between 25 and 80 NTU. Cortisol levels indicated minimal stress between 35 and 80 NTU and were elevated at low turbidities (5, 12 and 25 NTU). Expression of stress-related genes indicated significant responses for gst, hsp70 and glut2 in high turbidities (250 NTU), and principal component analysis on all measured genes revealed a clustering of 25, 35, 50 and 80 NTU separating the medium-turbidity treatments from low- and high-turbidity treatments. Taken together, these data demonstrate that turbidity levels that are either too low or too high affect delta

Suspended solids moderate the degradation and sorption of waste water-derived pharmaceuticals in estuarine waters.

Science.gov (United States)

Aminot, Yann; Fuster, Laura; Pardon, Patrick; Le Menach, Karyn; Budzinski, Hélène

2018-01-15

This study focuses on the fate of pharmaceuticals discharged into an estuarine environment, particularly into the Turbidity Maximum Zone (TMZ). Batch experiments were set up to investigate the factors regulating the degradation of 53 selected pharmaceuticals. Treated effluents from Bordeaux city (France) were mixed with water from the estuarine Garonne River during 4weeks under 6 characterized conditions in order to assess the influence of suspended particulates, sterilization, untreated wastewater input and dilution on the degradation kinetics. Of the 53 pharmaceuticals monitored, 43 were quantified at the initial time. Only 7 exhibited a persistent behavior (e.g. carbamazepine, meprobamate) while biotic degradation was shown to be the main attenuation process for 38 molecules (e.g. abacavir, ibuprofen highly degradable). Degradation was significantly enhanced by increasing concentrations of suspended solids. A persistence index based on the half-lives of the compounds has been calculated for each of the 43 pharmaceuticals to provide a practical estimate of their relative stability. The stability of pharmaceuticals in estuarine environments is likely to be highly variable and attenuated primarily by changes in suspended solid concentration. Copyright © 2017 Elsevier B.V. All rights reserved.

Deterministic and Advanced Statistical Modeling of Wind-Driven Sea

Science.gov (United States)

2015-07-06

It gives a ground for use an asymptotic approach for wind-driven seas in a spirit of our previous works [R16,R17]. Then we use simple...b𔃼)-—{b’’— b2 ) 1 - --r 2 b-k{\\b’\\2)--{b’k{\\b\\2)) ox *-(6’ 2) -. dx dx dx This equation has localized breather-type solution b{x,t) = B{x

Investigating Wind-Driven Rain Intrusion in Walls with the CARWASh

Science.gov (United States)

C.R. Boardman; Samuel V. Glass

2013-01-01

Wind-driven rain provides the primary external moisture load for exterior walls.Water absorption by the cladding, runoff, and penetration through the cladding or at details determine how a wall system performs. In this paper we describe a new laboratory facility that can create controlled outdoor and indoor conditions and use it to investigate the water...

Shifts in wind energy potential following land-use driven vegetation dynamics in complex terrain.

Science.gov (United States)

Fang, Jiannong; Peringer, Alexander; Stupariu, Mihai-Sorin; Pǎtru-Stupariu, Ileana; Buttler, Alexandre; Golay, Francois; Porté-Agel, Fernando

2018-10-15

Many mountainous regions with high wind energy potential are characterized by multi-scale variabilities of vegetation in both spatial and time dimensions, which strongly affect the spatial distribution of wind resource and its time evolution. To this end, we developed a coupled interdisciplinary modeling framework capable of assessing the shifts in wind energy potential following land-use driven vegetation dynamics in complex mountain terrain. It was applied to a case study area in the Romanian Carpathians. The results show that the overall shifts in wind energy potential following the changes of vegetation pattern due to different land-use policies can be dramatic. This suggests that the planning of wind energy project should be integrated with the land-use planning at a specific site to ensure that the expected energy production of the planned wind farm can be reached over its entire lifetime. Moreover, the changes in the spatial distribution of wind and turbulence under different scenarios of land-use are complex, and they must be taken into account in the micro-siting of wind turbines to maximize wind energy production and minimize fatigue loads (and associated maintenance costs). The proposed new modeling framework offers, for the first time, a powerful tool for assessing long-term variability in local wind energy potential that emerges from land-use change driven vegetation dynamics over complex terrain. Following a previously unexplored pathway of cause-effect relationships, it demonstrates a new linkage of agro- and forest policies in landscape development with an ultimate trade-off between renewable energy production and biodiversity targets. Moreover, it can be extended to study the potential effects of micro-climatic changes associated with wind farms on vegetation development (growth and patterning), which could in turn have a long-term feedback effect on wind resource distribution in mountainous regions. Copyright © 2018 Elsevier B.V. All rights

Beyond Tree Throw: Wind, Water, Rock and the Mechanics of Tree-Driven Bedrock Physical Weathering

Science.gov (United States)

Marshall, J. A.; Anderson, R. S.; Dawson, T. E.; Dietrich, W. E.; Minear, J. T.

2017-12-01

Tree throw is often invoked as the dominant process in converting bedrock to soil and thus helping to build the Critical Zone (CZ). In addition, observations of tree roots lifting sidewalk slabs, occupying cracks, and prying slabs of rock from cliff faces have led to a general belief in the power of plant growth forces. These common observations have led to conceptual models with trees at the center of the soil genesis process. This is despite the observation that tree throw is rare in many forested settings, and a dearth of field measurements that quantify the magnitude of growth forces. While few trees blow down, every tree grows roots, inserting many tens of percent of its mass below ground. Yet we lack data quantifying the role of trees in both damaging bedrock and detaching it (and thus producing soil). By combing force measurements at the tree-bedrock interface with precipitation, solar radiation, wind speed, and wind-driven tree sway data we quantified the magnitude and frequency of tree-driven soil-production mechanisms from two contrasting climatic and lithologic regimes (Boulder and Eel Creek CZ Observatories). Preliminary data suggests that in settings with relatively thin soils, trees can damage and detach rock due to diurnal fluctuations, wind response and rainfall events. Surprisingly, our data suggests that forces from roots and trunks growing against bedrock are insufficient to pry rock apart or damage bedrock although much more work is needed in this area. The frequency, magnitude and style of wind-driven tree forces at the bedrock interface varies considerably from one to another species. This suggests that tree properties such as mass, elasticity, stiffness and branch structure determine whether trees respond to gusts big or small, move at the same frequency as large wind gusts, or are able to self-dampen near-ground sway response to extended wind forces. Our measurements of precipitation-driven and daily fluctuations in root pressures exerted on

Treatment Wetland Aeration without Electricity? Lessons Learned from the First Experiment Using a Wind-Driven Air Pump

Directory of Open Access Journals (Sweden)

Johannes Boog

2016-11-01

Full Text Available Aerated treatment wetlands have become an increasingly recognized technology for treating wastewaters from domestic and various industrial origins. To date, treatment wetland aeration is provided by air pumps which require access to the energy grid. The requirement for electricity increases the ecological footprint of an aerated wetland and limits the application of this technology to areas with centralized electrical infrastructure. Wind power offers another possibility as a driver for wetland aeration, but its use for this purpose has not yet been investigated. This paper reports the first experimental trial using a simple wind-driven air pump to replace the conventional electric air blowers of an aerated horizontal subsurface flow wetland. The wind-driven air pump was connected to a two-year old horizontal flow aerated wetland which had been in continuous (24 h aeration since startup. The wind-driven aeration system functioned, however it was not specifically adapted to wetland aeration. As a result, treatment performance decreased compared to prior continuous aeration. Inconsistent wind speed at the site may have resulted in insufficient pressure within the aeration manifold, resulting in insufficient air supply to the wetland. This paper discusses the lessons learned during the experiment.

Effects of El Niño-driven changes in wind patterns on North Pacific albatrosses.

Science.gov (United States)

Thorne, L H; Conners, M G; Hazen, E L; Bograd, S J; Antolos, M; Costa, D P; Shaffer, S A

2016-06-01

Changes to patterns of wind and ocean currents are tightly linked to climate change and have important implications for cost of travel and energy budgets in marine vertebrates. We evaluated how El Niño-Southern Oscillation (ENSO)-driven wind patterns affected breeding Laysan and black-footed albatross across a decade of study. Owing to latitudinal variation in wind patterns, wind speed differed between habitat used during incubation and brooding; during La Niña conditions, wind speeds were lower in incubating Laysan (though not black-footed) albatross habitat, but higher in habitats used by brooding albatrosses. Incubating Laysan albatrosses benefited from increased wind speeds during El Niño conditions, showing increased travel speeds and mass gained during foraging trips. However, brooding albatrosses did not benefit from stronger winds during La Niña conditions, instead experiencing stronger cumulative headwinds and a smaller proportion of trips in tailwinds. Increased travel costs during brooding may contribute to the lower reproductive success observed in La Niña conditions. Furthermore, benefits of stronger winds in incubating habitat may explain the higher reproductive success of Laysan albatross during El Niño conditions. Our findings highlight the importance of considering habitat accessibility and cost of travel when evaluating the impacts of climate-driven habitat change on marine predators. © 2016 The Author(s).

Line-driven disk winds in active galactic nuclei: The critical importance of ionization and radiative transfer

Energy Technology Data Exchange (ETDEWEB)

Higginbottom, Nick; Knigge, Christian; Matthews, James H. [School of Physics and Astronomy, University of Southampton, Highfield, Southampton, SO17 1BJ (United Kingdom); Proga, Daniel [Department of Physics and Astronomy, University of Nevada, Las Vegas, 4505 South Maryland Parkway, Las Vegas, NV 89154-4002 (United States); Long, Knox S. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Sim, Stuart A., E-mail: nick_higginbottom@fastmail.fm [School of Mathematics and Physics, Queens University Belfast, University Road, Belfast, BT7 1NN (United Kingdom)

2014-07-01

Accretion disk winds are thought to produce many of the characteristic features seen in the spectra of active galactic nuclei (AGNs) and quasi-stellar objects (QSOs). These outflows also represent a natural form of feedback between the central supermassive black hole and its host galaxy. The mechanism for driving this mass loss remains unknown, although radiation pressure mediated by spectral lines is a leading candidate. Here, we calculate the ionization state of, and emergent spectra for, the hydrodynamic simulation of a line-driven disk wind previously presented by Proga and Kallman. To achieve this, we carry out a comprehensive Monte Carlo simulation of the radiative transfer through, and energy exchange within, the predicted outflow. We find that the wind is much more ionized than originally estimated. This is in part because it is much more difficult to shield any wind regions effectively when the outflow itself is allowed to reprocess and redirect ionizing photons. As a result, the calculated spectrum that would be observed from this particular outflow solution would not contain the ultraviolet spectral lines that are observed in many AGN/QSOs. Furthermore, the wind is so highly ionized that line driving would not actually be efficient. This does not necessarily mean that line-driven winds are not viable. However, our work does illustrate that in order to arrive at a self-consistent model of line-driven disk winds in AGN/QSO, it will be critical to include a more detailed treatment of radiative transfer and ionization in the next generation of hydrodynamic simulations.

Operational monitoring of turbidity in rivers: how satellites can contribute

Science.gov (United States)

Hucke, Dorothee; Hillebrand, Gudrun; Winterscheid, Axel; Kranz, Susanne; Baschek, Björn

2016-10-01

The applications of remote sensing in hydrology are diverse and offer significant benefits for water monitoring. Up to now, operational river monitoring and sediment management in Germany mainly rely on in-situ measurements and on results obtained from numerical modelling. Remote sensing by satellites has a great potential to supplement existing data with two-dimensional information on near-surface turbidity distributions at greater spatial scales than in-situ measurements can offer. Within the project WasMon-CT (WaterMonitoring-Chlorophyll/Turbidity), the Federal Institute of Hydrology (BfG) aims at the implementation of an operational monitoring of turbidity distributions based on satellite images (esp. Sentinel-2, Landsat7 and 8). Initially, selected federal inland and estuarine waterways will be addressed: Rhine, Elbe, Ems, Weser. WasMon-CT is funded within the German Copernicus activities. Within the project, a database of atmospherically corrected, geo-referenced turbidity data will be assembled. The collected corresponding meta-data will include aspects of satellite data as well as hydrological data, e.g. cloud cover and river run-off. Based on this catalogue of spatially linked meta-data, the satellite data will be selected by e.g. cloud cover or run-off. The permanently updated database will include past as well as recent satellite images. It is designed with a long-term perspective to optimize the existing in-situ measurement network, which will serve partly for calibration and partly as validation data set. The aim is to extend, but not to substitute, the existing frequent point measurements with spatially extensive, satellite-derived data from the near surface part of the water column. Here, turbidity is used as proxy for corresponding suspended sediment concentrations. For this, the relationship between turbidity and suspended sediment concentrations will be investigated. Products as e.g. longitudinal profiles or virtual measurement stations will be

Time-resolved PIV measurements of the atmospheric boundary layer over wind-driven surface waves

Science.gov (United States)

Markfort, Corey; Stegmeir, Matt

2017-11-01

Complex interactions at the air-water interface result in two-way coupling between wind-driven surface waves and the atmospheric boundary layer (ABL). Turbulence generated at the surface plays an important role in aquatic ecology and biogeochemistry, exchange of gases such as oxygen and carbon dioxide, and it is important for the transfer of energy and controlling evaporation. Energy transferred from the ABL promotes the generation and maintenance of waves. A fraction of the energy is transferred to the surface mixed layer through the generation of turbulence. Energy is also transferred back to the ABL by waves. There is a need to quantify the details of the coupled boundary layers of the air-water system to better understand how turbulence plays a role in the interactions. We employ time-resolved PIV to measure the detailed structure of the air and water boundary layers under varying wind and wave conditions in the newly developed IIHR Boundary-Layer Wind-Wave Tunnel. The facility combines a 30-m long recirculating water channel with an open-return boundary layer wind tunnel. A thick turbulent boundary layer is developed in the 1 m high air channel, over the water surface, allowing for the study of boundary layer turbulence interacting with a wind-driven wave field.

Wind power demonstration and siting problems. [for recharging electrically driven automobiles

Science.gov (United States)

Bergey, K. H.

1973-01-01

Technical and economic feasibility studies on a small windmill to provide overnight charging for an electrically driven car are reported. The auxiliary generator provides power for heating and cooling the vehicle which runs for 25 miles on battery power alone, and for 50 miles with the onboard charger operating. The blades for this windmill have a diameter of 12 feet and are coupled through to a conventional automobile alternator so that they are able to completely recharge car batteries in 8 hours. Optimization of a windmill/storage system requires detailed wind velocity information which permits rational sitting of wind power system stations.

Experimental Study of Wind-Opposed Buoyancy-Driven Natural Ventilation

OpenAIRE

Andersen, A.; Bjerre, M.; Chen, Z. D.; Heiselberg, Per; Li, Y.

2000-01-01

Natural ventilation driven by natural forces, i.e. wind and thermal buoyancy, is an environmentally friendly system for buildings and has been increasingly used around the world in recent years to mitigate the impact on the global environment due to the significant energy consumption by heating, ventilation and air-conditioning (HV AC). There is a need for the understanding and development of theories and tools related to the design, operation and control of natural ventilation systems.

Experimental Study of Wind-Opposed Buoyancy-Driven Natural Ventilation

DEFF Research Database (Denmark)

Andersen, A.; Bjerre, M.; Chen, Z. D.

Natural ventilation driven by natural forces, i.e. wind and thermal buoyancy, is an environmentally friendly system for buildings and has been increasingly used around the world in recent years to mitigate the impact on the global environment due to the significant energy consumption by heating......, ventilation and air-conditioning (HV AC). There is a need for the understanding and development of theories and tools related to the design, operation and control of natural ventilation systems....

Modelling and Analysis of Radial Flux Surface Mounted Direct-Driven PMSG in Small Scale Wind Turbine

Directory of Open Access Journals (Sweden)

Theint Zar Htet

2017-11-01

Full Text Available This paper presents the modelling and analysis of permanent magnet synchronous generator (PMSG which are used in direct driven small scale wind turbines. The 3 kW PM generator which is driven directly without gear system is analyzed by Ansoft Maxwell 2D RMxprt. The performance analysis of generator includes the cogging torque in two teeth, induced coil voltages under load, winding current under load, airgap flux density distribution and so on. The modelling analysis is based on the 2D finite element techniques. In an electrical machine, an accurate determination of the geometry parameters is a vital role. The proper performance results of 3kW PMSG in small scale wind turbine can be seen in this paper.

The influence of channel deepening on estuarine turbidity levels and dynamics, as exemplified by the Ems estuary

NARCIS (Netherlands)

de Jonge, V.N.; Schuttelaars, H.M.; van Beusekom, J.E.E.; Talke, S.A.|info:eu-repo/dai/nl/304823554; de Swart, H.E.|info:eu-repo/dai/nl/073449725

2014-01-01

Active deepening of tidal channels usually results in the alteration of the vertical and the horizontal tide. This may lead to concurrent significant increases in mean suspended matter concentrations (SPM) in coastal plain estuaries, the turbidity maximum (ETM) included. This is exemplified by an

Spectrum Analysis of Inertial and Subinertial Motions Based on Analyzed Winds and Wind-Driven Currents from a Primitive Equation General Ocean Circulation Model.

Science.gov (United States)

1982-12-01

1Muter.Te Motions Based on Ana lyzed Winds and wind-driven December 1982 Currents from. a Primitive Squat ion General a.OW -love"*..* Oean Circulation...mew se"$ (comeS.... do oISN..u am ae~ 00do OWaor NUN Fourier and Rotary Spc , Analysis Modeled Inertial and Subinrtial Motion 4 Primitive Equation

Measurements of atmospheric turbidity in an arc downwind of St. Louis

International Nuclear Information System (INIS)

Wesely, M.L.

1975-01-01

A preliminary analysis of the data obtained with use of the dichopyranometer indicates that large decreases in the direct-beam irradiance occurred during August 9 - 11 at several of the monitoring sites, four of which were located on an arc about 110 km from the Gateway Arch, Jefferson Expansion National Memorial, a well-known landmark in St. Louis. The four sites have azimuthal bearings east of north from the Arch of --16 deg (EPA, Glasgow), 9 deg (Waverly), 24 deg (Sangamon Co.), and 31 deg (Sloman farm). There are figures that show the variation of four-hour averages of tau at these sites. Also shown are the turbidity measurements at the St. Louis site, which was actually in Illinois at RAMS site 103, located about 7 km northeast of the Gateway Arch in a suburban area. The urban plume from St. Louis was expected to be about 20 deg wide and perhaps 10 to 20 deg greater in azimuth than the surface wind direction would indicate. Thus, on August 8, the effects of the plume should have been detected at the site on the azimuthal bearing of 24 deg, but this was not evident from the data. On August 9, the plume should have been east of, or at a greater azimuthal bearing than, the easternmost site (at 31 deg), and this may be supported by the existence of the slightly greater values of turbidity at that easternmost site. However, on August 10 and 11, similar southwesterly wind directions were not always associated with a maximum in turbidity at the easternmost site. Hence, it appears that the St. Louis plume did not consistently have a dominant role in causing atmospheric turbidity

Short time-scale wind forced variability in the Río de la Plata Estuary and its role on ichthyoplankton retention

Science.gov (United States)

Simionato, C. G.; Berasategui, A.; Meccia, V. L.; Acha, M.; Mianzan, H.

2008-01-01

The Río de la Plata Estuary presents a strong bottom salinity front located over a submerged shoal. Apparently favored by retention processes, it is a spawning ground for several coastal fishes. This estuary is very shallow and essentially wind driven and, moreover, in time scales relevant to biota, estuarine circulation is wind dominated and highly variable. Two intriguing questions are, therefore, how this system can favor retention and what the involved mechanisms are. This paper qualitatively explores mechanisms involved in the estuary where retention is favored applying numerical simulations in which neutral particles - simulating fish eggs and early larvae - are released along the bottom frontal zone and tracked for different wind conditions. Results suggest that retentive features can be a consequence of estuarine response to natural wind variability acting over bathymetric features. For winds from most directions, particles either remain trapped near their launching position or move northeastward to southwestward along the shoal. As alternation of winds that favor along-shoal motion is the dominant feature of wind variability in the region, a retentive scenario results from prevailing wind variability. Additionally, winds that tend to export particles with a poor chance of being restored to the front are neither frequent nor persistent. Results show, therefore, that physical forcing alone might generate a retentive scenario at the inner part of this estuary. The physical retention mechanism is more effective for bottom than for surface launched particles. Wind statistics indicate that the proposed mechanism has different implications for retention along the seasons. Spring is the most favorable season, followed by summer, when particles would have a larger propensity to reach the southern area of the estuary (Samborombón Bay). Fall and winter are increasingly less favorable. All these features are consistent with patterns observed in the region in

TURBULENCE IN THE SUB-ALFVENIC SOLAR WIND DRIVEN BY REFLECTION OF LOW-FREQUENCY ALFVEN WAVES

International Nuclear Information System (INIS)

Verdini, A.; Velli, M.; Buchlin, E.

2009-01-01

We study the formation and evolution of a turbulent spectrum of Alfven waves driven by reflection off the solar wind density gradients, starting from the coronal base up to 17 solar radii, well beyond the Alfvenic critical point. The background solar wind is assigned and two-dimensional shell models are used to describe nonlinear interactions. We find that the turbulent spectra are influenced by the nature of the reflected waves. Close to the base, these give rise to a flatter and steeper spectrum for the outgoing and reflected waves, respectively. At higher heliocentric distance both spectra evolve toward an asymptotic Kolmogorov spectrum. The turbulent dissipation is found to account for at least half of the heating required to sustain the background imposed solar wind and its shape is found to be determined by the reflection-determined turbulent heating below 1.5 solar radii. Therefore, reflection and reflection-driven turbulence are shown to play a key role in the acceleration of the fast solar wind and origin of the turbulent spectrum found at 0.3 AU in the heliosphere.

Implementation, Comparison and Application of an Average Simulation Model of a Wind Turbine Driven Doubly Fed Induction Generator

Directory of Open Access Journals (Sweden)

Lidula N. Widanagama Arachchige

2017-10-01

Full Text Available Wind turbine driven doubly-fed induction generators (DFIGs are widely used in the wind power industry. With the increasing penetration of wind farms, analysis of their effect on power systems has become a critical requirement. This paper presents the modeling of wind turbine driven DFIGs using the conventional vector controls in a detailed model of a DFIG that represents power electronics (PE converters with device level models and proposes an average model eliminating the PE converters. The PSCAD/EMTDC™ (4.6 electromagnetic transient simulation software is used to develop the detailed and the proposing average model of a DFIG. The comparison of the two models reveals that the designed average DFIG model is adequate for simulating and analyzing most of the transient conditions.

The Swift Turbidity Marker

Science.gov (United States)

Omar, Ahmad Fairuz; MatJafri, Mohd Zubir

2011-01-01

The Swift Turbidity Marker is an optical instrument developed to measure the level of water turbidity. The components and configuration selected for the system are based on common turbidity meter design concepts but use a simplified methodology to produce rapid turbidity measurements. This work is aimed at high school physics students and is the…

Evaluation of Discharge Coefficients for Window Openings in Wind Driven Natural Ventilation

DEFF Research Database (Denmark)

Heiselberg, Per; Sandberg, Mats

2006-01-01

This paper describes the classical approach for calculation of wind driven airflow through large openings in buildings and discusses the fulfilment of the limiting assumptions. It is demonstrated that the limiting assumptions are not fulfilled for large openings in buildings for cross ventilation...... cannot be regarded as a constant and it is very difficult to estimate correct values resulting in less accuracy of prediction of natural ventilation.......This paper describes the classical approach for calculation of wind driven airflow through large openings in buildings and discusses the fulfilment of the limiting assumptions. It is demonstrated that the limiting assumptions are not fulfilled for large openings in buildings for cross ventilation......, and therefore, the classical approach is not appropriate for prediction of airflow through large openings in buildings in the cross ventilation case. Using the approach for real openings and estimating the discharge coefficient for window openings has also not been very successful. The discharge coefficient...

Sedimentological regimes for turbidity currents: Depth-averaged theory

Science.gov (United States)

Halsey, Thomas C.; Kumar, Amit; Perillo, Mauricio M.

2017-07-01

Turbidity currents are one of the most significant means by which sediment is moved from the continents into the deep ocean; their properties are interesting both as elements of the global sediment cycle and due to their role in contributing to the formation of deep water oil and gas reservoirs. One of the simplest models of the dynamics of turbidity current flow was introduced three decades ago, and is based on depth-averaging of the fluid mechanical equations governing the turbulent gravity-driven flow of relatively dilute turbidity currents. We examine the sedimentological regimes of a simplified version of this model, focusing on the role of the Richardson number Ri [dimensionless inertia] and Rouse number Ro [dimensionless sedimentation velocity] in determining whether a current is net depositional or net erosional. We find that for large Rouse numbers, the currents are strongly net depositional due to the disappearance of local equilibria between erosion and deposition. At lower Rouse numbers, the Richardson number also plays a role in determining the degree of erosion versus deposition. The currents become more erosive at lower values of the product Ro × Ri, due to the effect of clear water entrainment. At higher values of this product, the turbulence becomes insufficient to maintain the sediment in suspension, as first pointed out by Knapp and Bagnold. We speculate on the potential for two-layer solutions in this insufficiently turbulent regime, which would comprise substantial bedload flow with an overlying turbidity current.

Coastal upwelling by wind-driven forcing in Jervis Bay, New South Wales: A numerical study for 2011

Science.gov (United States)

Sun, Youn-Jong; Jalón-Rojas, Isabel; Wang, Xiao Hua; Jiang, Donghui

2018-06-01

The Princeton Ocean Model (POM) was used to investigate an upwelling event in Jervis Bay, New South Wales (SE Australia), with varying wind directions and strengths. The POM was adopted with a downscaling approach for the regional ocean model one-way nested to a global ocean model. The upwelling event was detected from the observed wind data and satellite sea surface temperature images. The validated model reproduced the upwelling event showing the input of bottom cold water driven by wind to the bay, its subsequent deflection to the south, and its outcropping to the surface along the west and south coasts. Nevertheless, the behavior of the bottom water that intruded into the bay varied with different wind directions and strengths. Upwelling-favorable wind directions for flushing efficiency within the bay were ranked in the following order: N (0°; northerly) > NNE (30°; northeasterly) > NW (315°; northwesterly) > NE (45°; northeasterly) > ENE (60°; northeasterly). Increasing wind strengths also enhance cold water penetration and water exchange. It was determined that wind-driven downwelling within the bay, which occurred with NNE, NE and ENE winds, played a key role in blocking the intrusion of the cold water upwelled through the bay entrance. A northerly wind stress higher than 0.3 N m-2 was required for the cold water to reach the northern innermost bay.

Rayleigh-Taylor and wind-driven instabilities of the nighttime equatorial ionosphere

International Nuclear Information System (INIS)

Chiu, Y.T.; Straus, J.M.

1979-01-01

We have made a thorough re-examination of the Rayleigh-Taylor instability in the nighttime equatorial ionosphere from approx.100 km to the bottomside F region. We have taken into account explicitly the following effects which have been ignored by other workers in various combinations: (1) The eastward drift of the ionosphere caused by the nighttime polarization electric field, (2) the eastward nighttime neutral wind, and (3) recombination in the F and E regions. We found that, well below the bottomside F region, the Rayleigh-Taylor mode can be unstable and is driven by an eastward neutral wind rather than by gravitational drift. Formation of ionospheric bubbles below the bottomside F region is consistent with the observation of lower ionospheric ions in F region ionospheric holes; furthermore, seasonal and shorter term variations in spread-F occurrence may be associated with variations in the neutral wind and polarization electric field

Data-driven wind plant control

NARCIS (Netherlands)

Gebraad, P.M.O.

2014-01-01

Each wind turbine in a cluster of wind turbines (a wind power plant) can influence the performance of other turbines through the wake that forms downstream of its rotor. The wake has a reduced wind velocity, since the turbine extracts energy from the flow, and the obstruction by the wind turbine

WIND-DRIVEN ACCRETION IN PROTOPLANETARY DISKS. II. RADIAL DEPENDENCE AND GLOBAL PICTURE

Energy Technology Data Exchange (ETDEWEB)

Bai Xuening, E-mail: xbai@cfa.harvard.edu [Institute for Theory and Computation, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-51, Cambridge, MA 02138 (United States)

2013-08-01

Non-ideal magnetohydrodynamical effects play a crucial role in determining the mechanism and efficiency of angular momentum transport as well as the level of turbulence in protoplanetary disks (PPDs), which are the key to understanding PPD evolution and planet formation. It was shown in our previous work that at 1 AU, the magnetorotational instability (MRI) is completely suppressed when both ohmic resistivity and ambipolar diffusion (AD) are taken into account, resulting in a laminar flow with accretion driven by magnetocentrifugal wind. In this work, we study the radial dependence of the laminar wind solution using local shearing-box simulations. The scaling relation on the angular momentum transport for the laminar wind is obtained, and we find that the wind-driven accretion rate can be approximated as M-dot approx. 0.91 x 10{sup -8}R{sub AU}{sup 1.21}(B{sub p}/10 mG){sup 0.93} M{sub Sun} yr{sup -1}, where B{sub p} is the strength of the large-scale poloidal magnetic field threading the disk. The result is independent of disk surface density. Four criteria are outlined for the existence of the laminar wind solution: (1) ohmic resistivity dominated the midplane region, (2) the AD-dominated disk upper layer, (3) the presence of a (not too weak) net vertical magnetic flux, and (4) sufficiently well-ionized gas beyond the disk surface. All these criteria are likely to be met in the inner region of the disk from {approx}0.3 AU to about 5-10 AU for typical PPD accretion rates. Beyond this radius, the angular momentum transport is likely to proceed due to a combination of the MRI and disk wind, and eventually completely dominated by the MRI (in the presence of strong AD) in the outer disk. Our simulation results provide key ingredients for a new paradigm on the accretion processes in PPDs.

Origins of wind-driven intraseasonal sea level variations in the North Indian Ocean coastal waveguide

Digital Repository Service at National Institute of Oceanography (India)

Suresh, I.; Vialard, J.; Lengaigne, M.; Han, W.; Mc; Durand, F.; Muraleedharan, P.M.

version: Geophys. Res. Lett., vol.40(21); 2013; 5740-5744 Origins of wind-driven intraseasonal sea level variations in the North Indian Ocean coastal waveguide I. Suresh1, J. Vialard2, M. Lengaigne2, W. Han3, J. McCreary4, F. Durand5, P.M. Muraleedharan1... reversing winds. These wind variations drive seasonal equatorial Kelvin and Rossby wave responses. The seasonal equatorial Kelvin waves propagate into the North Indian Ocean (hereafter NIO) as coastal Kelvin waves [McCreary et al., 1993]. As a result...

Spectral decomposition of regulatory thresholds for climate-driven fluctuations in hydro- and wind power availability

Science.gov (United States)

Wörman, A.; Bottacin-Busolin, A.; Zmijewski, N.; Riml, J.

2017-08-01

Climate-driven fluctuations in the runoff and potential energy of surface water are generally large in comparison to the capacity of hydropower regulation, particularly when hydropower is used to balance the electricity production from covarying renewable energy sources such as wind power. To define the bounds of reservoir storage capacity, we introduce a dedicated reservoir volume that aggregates the storage capacity of several reservoirs to handle runoff from specific watersheds. We show how the storage bounds can be related to a spectrum of the climate-driven modes of variability in water availability and to the covariation between water and wind availability. A regional case study of the entire hydropower system in Sweden indicates that the longest regulation period possible to consider spans from a few days of individual subwatersheds up to several years, with an average limit of a couple of months. Watershed damping of the runoff substantially increases the longest considered regulation period and capacity. The high covariance found between the potential energy of the surface water and wind energy significantly reduces the longest considered regulation period when hydropower is used to balance the fluctuating wind power.

Spatio-temporal analysis of prodelta dynamics by means of new satellite generation: the case of Po river by Landsat-8 data

Science.gov (United States)

Manzo, Ciro; Braga, Federica; Zaggia, Luca; Brando, Vittorio Ernesto; Giardino, Claudia; Bresciani, Mariano; Bassani, Cristiana

2018-04-01

This paper describes a procedure to perform spatio-temporal analysis of river plume dispersion in prodelta areas by multi-temporal Landsat-8-derived products for identifying zones sensitive to water discharge and for providing geostatistical patterns of turbidity linked to different meteo-marine forcings. In particular, we characterized the temporal and spatial variability of turbidity and sea surface temperature (SST) in the Po River prodelta (Northern Adriatic Sea, Italy) during the period 2013-2016. To perform this analysis, a two-pronged processing methodology was implemented and the resulting outputs were analysed through a series of statistical tools. A pixel-based spatial correlation analysis was carried out by comparing temporal curves of turbidity and SST hypercubes with in situ time series of wind speed and water discharge, providing correlation coefficient maps. A geostatistical analysis was performed to determine the spatial dependency of the turbidity datasets per each satellite image, providing maps of correlation and variograms. The results show a linear correlation between water discharge and turbidity variations in the points more affected by the buoyant plumes and along the southern coast of Po River delta. Better inverse correlation was found between turbidity and SST during floods rather than other periods. The correlation maps of wind speed with turbidity show different spatial patterns depending on local or basin-scale wind effects. Variogram maps identify different spatial anisotropy structures of turbidity in response to ambient conditions (i.e. strong Bora or Scirocco winds, floods). Since the implemented processing methodology is based on open source software and free satellite data, it represents a promising tool for the monitoring of maritime ecosystems and to address water quality analyses and the investigations of sediment dynamics in estuarine and coastal waters.

Dynamics of the turbidity maximum zone in a macrotidal estuary (the Gironde, France): Observations from field and MODIS satellite data

Science.gov (United States)

Doxaran, David; Froidefond, Jean-Marie; Castaing, Patrice; Babin, Marcel

2009-02-01

Over a 1-year period, field and satellite measurements of surface water turbidity were combined in order to study the dynamics of the turbidity maximum zone (TM) in a macrotidal estuary (the Gironde, France). Four fixed platforms equipped with turbidity sensors calibrated to give the suspended particulate matter (SPM) concentration provided continuous information in the upper estuary. Full resolution data recorded by the moderate resolution imaging spectroradiometer (MODIS) sensors onboard the Terra and Aqua satellite platforms provided information in the central and lower estuary twice a day (depending on cloud cover). Field data were used to validate a recently developed SPM quantification algorithm applied to the MODIS 'surface reflectance' product. The algorithm is based on a relationship between the SPM concentration and a reflectance ratio of MODIS bands 2 (near-infrared) and 1 (red). Based on 62 and 75 match-ups identified in 2005 with MODIS Terra and Aqua data, the relative uncertainty of the algorithm applied to these sensors was found to be 22 and 18%, respectively. Field measurements showed the tidal variations of turbidity in the upper estuary, while monthly-averaged MODIS satellite data complemented by field data allowed observing the monthly movements of the TM in the whole estuary. The trapping of fine sediments occurred in the upper estuary during the period of low river flow. This resulted in the formation of a highly concentrated TM during a 4-month period. With increasing river flow, the TM moved rapidly to the central estuary. A part of the TM detached, moved progressively in the lower estuary and was finally either massively exported to the ocean during peak floods or temporary trapped (settled) on intertidal mudflats. The massive export to the ocean was apparently the result of combined favorable environmental conditions: presence of fluid mud near the mouth, high river flow, high tides and limited wind speeds. The mean SPM concentration

The complex early life history of a marine estuarine-opportunist fish species, Solea turbynei (Soleidae from temperate South Africa

Directory of Open Access Journals (Sweden)

Nadine A. Strydom

2015-06-01

Full Text Available The early life history stages and ecology of Solea turbynei, a marine estuarine-opportunist species, is described from nursery areas in Algoa Bay, South Africa. Early life history stages were collected over multiple years from known nursery habitats using plankton, fyke and larval seine nets. The larvae are described using morphometric measurements, meristic counts and pigmentation based on 29 individuals. Solea turbynei is differentiated from other Soleidae by the small size at flexion (3-4 mm, low myomere count and presence of two characteristic blotches of pigment on the dorsal fin. This species has a unique early life history strategy in that the larvae progressively span nearshore, surf zone and estuarine habitats with ontogeny. Abundance of preflexion stages peaks in summer in nearshore waters, indicative of peak spawning period but preflexion larvae are present throughout the year, indicating protracted spawning by adults. At flexion stage, larvae utilize surf zones where metamorphosis and settlement takes place. Early juveniles migrate into the sandy lower reaches of estuaries, after which fish take up residency to adulthood. Warm water is important for larval growth and survival in the nearshore, while turbidity shows a positive relationship with recruitment into estuarine nurseries.

Radiatively-driven winds: model improvements, ionization balance and the infared spectrum

International Nuclear Information System (INIS)

Castor, J.I.

1979-01-01

Recent improvements to theoretical stellar wind models and the results of empirical modelling of the ionization balance and the infrared continuum are discussed. The model of a wind driven by radiation pressure in spectral lines is improved by accounting for overlap of the driving lines, dependence of ionization balance on density, and stellar rotation. These effects produce a softer velocity law than that given by Castor, Abbott and Klein (1975). The ionization balance in zeta Puppis is shown to agree with that estimated for an optically thick wind at a gas temperature of 60,000 K. The ionization model is not unique. The infrared continuum of zeta Pup measured by Barlow and Cohen is fitted to a cool model with a linear rise of velocity with radius; this fit is also not unique. It is concluded that one should try to find a model that fits several kinds of evidence simultaneously. (Auth.)

Ecology of Estuarine Macrobenthos

NARCIS (Netherlands)

Herman, P.M.J.; Middelburg, J.J.; Koppel, J. van de; Heip, C.H.R.

1999-01-01

Macrobenthos is an important component of estuarine ecosystems. Based on a cross-system comparison, we show that estuarine macrobenthos may directly process a significant portion of the system-wide primary production, and that estuarine macrobenthic biomass may be predicted from primary production

Research of Intelligent Turbidity Sensor

OpenAIRE

Licai Zhang; Yaoguang Wei; Yingyi Chen; Daoliang Li; Lihua Zeng

2014-01-01

Turbidity is an important index to evaluate the water quality. Turbidity can reflect the effects of insoluble substances that contain bait and seston on water. Traditional methods of turbidity detection are complicated, they have low efficiency and poor reliability. To solve the turbidity detection problem in aquaculture, an intelligent optical turbidity sensor which is based on scattering theory has been proposed in this paper. After analyzing the quality characteristics of aquaculture water...

Ecosystem variability along the estuarine salinity gradient: Examples from long-term study of San Francisco Bay

Science.gov (United States)

Cloern, James E.; Jassby, Alan D.; Schraga, Tara; Kress, Erica S.; Martin, Charles A.

2017-01-01

The salinity gradient of estuaries plays a unique and fundamental role in structuring spatial patterns of physical properties, biota, and biogeochemical processes. We use variability along the salinity gradient of San Francisco Bay to illustrate some lessons about the diversity of spatial structures in estuaries and their variability over time. Spatial patterns of dissolved constituents (e.g., silicate) can be linear or nonlinear, depending on the relative importance of river-ocean mixing and internal sinks (diatom uptake). Particles have different spatial patterns because they accumulate in estuarine turbidity maxima formed by the combination of sinking and estuarine circulation. Some constituents have weak or no mean spatial structure along the salinity gradient, reflecting spatially distributed sources along the estuary (nitrate) or atmospheric exchanges that buffer spatial variability of ecosystem metabolism (dissolved oxygen). The density difference between freshwater and seawater establishes stratification in estuaries stronger than the thermal stratification of lakes and oceans. Stratification is strongest around the center of the salinity gradient and when river discharge is high. Spatial distributions of motile organisms are shaped by species-specific adaptations to different salinity ranges (shrimp) and by behavioral responses to environmental variability (northern anchovy). Estuarine spatial patterns change over time scales of events (intrusions of upwelled ocean water), seasons (river inflow), years (annual weather anomalies), and between eras separated by ecosystem disturbances (a species introduction). Each of these lessons is a piece in the puzzle of how estuarine ecosystems are structured and how they differ from the river and ocean ecosystems they bridge.

Transient, tidal-scale, nitrogen transformations in an estuarine turbidity maximum-fluid mud system (The Gironde, S.W. France)

NARCIS (Netherlands)

Abril, G.; Riou, S.A.; Etcheber, H.; Frankignoulle, M.; De Wit, R.; Middelburg, J.J.

2000-01-01

The maximum turbidity zone (MTZ) of the Gironde Estuary is a site of important mineralization of particulate organic nitrogen. Moreover, this MTZ is characterized by intense cycles of settling and resuspension of anoxic fluid mud at both tidal and neap-spring time-scales. In the upper layer of the

The theory of radiation driven stellar winds and the Wolf-Rayet phenomenon

International Nuclear Information System (INIS)

Abbott, D.C.

1982-01-01

The author considers the question of whether the mass loss observed from Wolf-Rayet stars can be explained by a version of wind theory which is scaled to the conditions found in the envelopes of Wolf-Rayet stars. He discusses the following topics: - The calculated radiation pressure in OB stars, and its dependence on temperature, density, and chemical composition. - A comparison between predicted and observed mass loss rates and terminal velocities for OB stars. - The applicability of the standard radiation driven wind models to Wolf-Rayet stars. - Speculations on how Wolf-Rayet stars achieve their enormous mass loss rates within the context of the radiation pressure mechanism. (Auth.)

The steady state solutions of radiatively driven stellar winds for a non-Sobolev, pure absorption model

International Nuclear Information System (INIS)

Poe, C.H.; Owocki, S.P.; Castor, J.I.

1990-01-01

The steady state solution topology for absorption line-driven flows is investigated for the condition that the Sobolev approximation is not used to compute the line force. The solution topology near the sonic point is of the nodal type with two positive slope solutions. The shallower of these slopes applies to reasonable lower boundary conditions and realistic ion thermal speed v(th) and to the Sobolev limit of zero of the usual Castor, Abbott, and Klein model. At finite v(th), this solution consists of a family of very similar solutions converging on the sonic point. It is concluded that a non-Sobolev, absorption line-driven flow with a realistic values of v(th) has no uniquely defined steady state. To the extent that a pure absorption model of the outflow of stellar winds is applicable, radiatively driven winds should be intrinsically variable. 34 refs

Wind-driven marine phytoplank blooms: Satellite observation and analysis

Science.gov (United States)

Tang, DanLing

2016-07-01

Algal bloom is defined as a rapid increase or accumulation in biomass in an aquatic system. It not only can increase the primary production but also could result in negative ecological consequence, e.g.,Harmful Algal Blooms (HABs). According to the classic theory for the formation of algal blooms "critical depth" and "eutrophication", oligotrophic sea area is usually difficult to form a large area of algal blooms, and actuallythe traditional observation is only sporadic capture to the existence of algal blooms.Taking full advantage of multiple data of satellite remote sensing , this study introduces "Wind-driven algal blooms in open oceans: observation and mechanisms" It explained except classic coastal Ekman transport, the wind through a variety of mechanisms affecting the formation of algal blooms. Proposed a conceptual model of "Strong wind -upwelling-nutrient-phytoplankton blooms" in Western South China Sea (SCS) to assess role of wind-induced advection transport in phytoplankton bloom formation. It illustrates the nutrient resources that support long-term offshore phytoplankton blooms in the western SCS; (2)Proposal of the theory that "typhoons cause vertical mixing, induce phytoplankton blooms", and quantify their important contribution to marine primary production; Proposal a new ecological index for typhoon. Proposed remote sensing inversion models. (3)Finding of the spatial and temporaldistributions pattern of harmful algal bloom (HAB)and species variations of HAB in the South Yellow Sea and East China Sea, and in the Pearl River estuary, and their oceanic dynamic mechanisms related with monsoon; The project developed new techniques and generated new knowledge, which significantly improved understanding of the formation mechanisms of algal blooms. The proposed "wind-pump" mechanism integrates theoretical system combined "ocean dynamics, development of algal blooms, and impact on primary production", which will benefit fisheries management. These

Standard test method to determine the performance of tiled roofs to wind-driven rain

Directory of Open Access Journals (Sweden)

Sánchez de Rojas, M. I.

2008-09-01

Full Text Available The extent to which roof coverings can resist water penetration from the combination of wind and rain, commonly referred to as wind driven rain, is important for the design of roofs. A new project of European Standard prEN 15601 (1 specifies a method of test to determine the performance of the roof covering against wind driven rain. The combined action of wind and rain varies considerably with geographical location of a building and the associated differences in the rain and wind climate. Three windrain conditions and one deluge condition covering Northern Europe Coastal, Central Europe and Southern Europe are specified in the project standard, each subdivided into four wind-speeds and rainfall rates to be applied to the test. The project does not contain information on the level of acceptable performance.Para el diseño de los tejados es importante determinar el punto hasta el cual éstos pueden resistirse a la penetración de agua causada por la combinación de viento y lluvia. Un nuevo proyecto de Norma Europeo prEN 15601 (1 especifica un método de ensayo para determinar el comportamiento del tejado frente a la combinación de viento y lluvia. La acción combinada de viento y lluvia varía considerablemente con la situación geográfica de un edificio y las diferencias asociadas al clima de la lluvia y del viento. El proyecto de norma especifica las condiciones de viento y lluvia y una condición de diluvio para cada una de las tres zonas de Europa: Europa del Norte y Costera, Europa Central y Europa del Sur, cada una subdividida en cuatro condiciones de velocidades de viento y caudal de lluvia para ser aplicadas en los ensayos. El proyecto no contiene la información sobre condiciones aceptables.

Tidal flushing and wind driven circulation of Ahe atoll lagoon (Tuamotu Archipelago, French Polynesia) from in situ observations and numerical modelling

International Nuclear Information System (INIS)

Dumas, F.; Le Gendre, R.; Thomas, Y.; Andréfouët, S.

2012-01-01

Hydrodynamic functioning and water circulation of the semi-closed deep lagoon of Ahe atoll (Tuamotu Archipelago, French Polynesia) were investigated using 1 year of field data and a 3D hydrodynamical model. Tidal amplitude averaged less than 30 cm, but tide generated very strong currents (2 m s −1 ) in the pass, creating a jet-like circulation that partitioned the lagoon into three residual circulation cells. The pass entirely flushed excess water brought by waves-induced radiation stress. Circulation patterns were computed for climatological meteorological conditions and summarized with stream function and flushing time. Lagoon hydrodynamics and general overturning circulation was driven by wind. Renewal time was 250 days, whereas the e-flushing time yielded a lagoon-wide 80-days average. Tide-driven flush through the pass and wind-driven overturning circulation designate Ahe as a wind-driven, tidally and weakly wave-flushed deep lagoon. The 3D model allows studying pearl oyster larvae dispersal in both realistic and climatological conditions for aquaculture applications.

Reversal of subtidal dune asymmetries caused by seasonally reversing wind-driven currents in Torres Strait, northeastern Australia

Science.gov (United States)

Harris, Peter T.

1991-07-01

Large subtidal sand dunes (sandwaves) located in Adolphus Channel, Torres Strait, have been observed to reverse their asymmetric orientation between September-February. This has been attributed to a reversal in wind-driven currents, which flow westward during the SE trade season (April-November) and eastwards during the NW monsoon season [December-March: HARRIS (1989) Continental Shelf Research, 9, 981-1002]. Observations in September 1988 and February 1989 from another area of dunes in Torres Strait corroborate this asymmetry reversal pattern. The results indicate that such reversals may be common in Torres Strait and in other areas where subtidal bedforms are subject to modification by superimposed, seasonally reversing, wind-driven currents.

Simulation of turbid underflows generated by the plunging of a river

Science.gov (United States)

Kassem, Ahmed; Imran, Jasim

2001-07-01

When the density of sediment-laden river water exceeds that of the lake or ocean into which it discharges, the river plunges to the bottom of the receiving water body and continues to flow as a hyperpycnal flow. These particle-laden underflows, also known as turbidity currents, can travel remarkable distances and profoundly influence the seabed morphology from shoreline to abyss by depositing, eroding, and dispersing large quantities of sediment particles. Here we present a new approach to investigating the transformation of a plunging river flow into a turbidity current. Unlike previous workers using experimental and numerical treatments, we consider the evolution of a turbidity current from a river as different stages of a single flow process. From initial commotion to final stabilization, the transformation of a river (open channel flow) into a density-driven current (hyperpycnal flow) is captured in its entirety by a numerical model. Successful implementation of the model in laboratory and field cases has revealed the dynamics of a complex geophysical flow that is extremely difficult to observe in the field or model in the laboratory.

Modeling X-ray Absorbers in AGNs with MHD-Driven Accretion-Disk Winds

Science.gov (United States)

Fukumura, Keigo; Kazanas, D.; Shrader, C. R.; Tombesi, F.; Contopoulos, J.; Behar, E.

2013-04-01

We have proposed a systematic view of the observed X-ray absorbers, namely warm absorbers (WAs) in soft X-ray and highly-ionized ultra-fast outflows (UFOs), in the context of magnetically-driven accretion-disk wind models. While potentially complicated by variability and thermal instability in these energetic outflows, in this simplistic model we have calculated 2D kinematic field as well as density and ionization structure of the wind with density profile of 1/r corresponding to a constant column distribution per decade of ionization parameter. In particular we show semi-analytically that the inner layer of the disk-wind manifests itself as the strongly-ionized fast outflows while the outer layer is identified as the moderately-ionized absorbers. The computed characteristics of these two apparently distinct absorbers are consistent with X-ray data (i.e. a factor of ~100 difference in column and ionization parameters as well as low wind velocity vs. near-relativistic flow). With the predicted contour curves for these wind parameters one can constrain allowed regions for the presence of WAs and UFOs.The model further implies that the UFO's gas pressure is comparable to that of the observed radio jet in 3C111 suggesting that the magnetized disk-wind with density profile of 1/r is a viable agent to help sustain such a self-collimated jet at small radii.

Imperfections of the North-Atlantic wind-driven ocean circulation: continental geometry and windstress shape

NARCIS (Netherlands)

Dijkstra, H.A.; Molemaker, M.J.

1998-01-01

Multiple equilibria of the wind-driven gyres have been found in idealized quasi- geostrophic and shallow water models.In this paper we demonstrate that multiple equilibria persist within a reduced gravity shallow water model under quite realis- tic continental geometry and windstress orcing for

Ergosphere-driven winds

International Nuclear Information System (INIS)

Punsly, B.; Coroniti, F.V.

1990-01-01

This paper is a discussion of a physical mechanism that allows large-scale magnetic fields to torque rapidly rotating black holes in an astrophysical context. The physics which is involved is that plasma in the ergosphere must rotate. Thus, if ergospheric plasma gets frozen onto large-scale magnetic field lines, then it can drive a magnetic wind to infinity, as is conjectured to occur in field-aligned pulsars. Included in this paper is a discussion of ingoing magnetic winds that accrete either toward the event horizon or to the equatorial plane in the ergosphere. 31 refs

Turbidity Current Bedforms

NARCIS (Netherlands)

Cartigny, Matthieu; Postma, G.

2017-01-01

Turbidity currents in the submarine seascape are what river flows are in terrestrial landscapes. While rivers transport sediment from the mountains through valleys towards the sea, turbidity currents transport sediment from the shallow marine realms through canyons towards the deeper abyssal plains.

Generation of electricity by wind power

Energy Technology Data Exchange (ETDEWEB)

Golding, E W

1976-01-01

Information on wind power is presented concerning the history of windmills; estimation of the energy obtainable from the wind; wind characteristics and distribution; wind power sites; wind surveys; wind flow over hills; measurement of wind velocity; wind structure and its determination; wind data and energy estimation; testing of wind driven ac generators; wind-driven machines; propeller type windmills; plants for isolated premises and small communities; economy of wind power generation; construction costs for large wind-driven generators; relationship of wind power to other power sources; research and development; and international cooperation.

Analysis of Dynamic Behavior of Multiple-Stage Planetary Gear Train Used in Wind Driven Generator

Directory of Open Access Journals (Sweden)

Jungang Wang

2014-01-01

Full Text Available A dynamic model of multiple-stage planetary gear train composed of a two-stage planetary gear train and a one-stage parallel axis gear is proposed to be used in wind driven generator to analyze the influence of revolution speed and mesh error on dynamic load sharing characteristic based on the lumped parameter theory. Dynamic equation of the model is solved using numerical method to analyze the uniform load distribution of the system. It is shown that the load sharing property of the system is significantly affected by mesh error and rotational speed; load sharing coefficient and change rate of internal and external meshing of the system are of obvious difference from each other. The study provides useful theoretical guideline for the design of the multiple-stage planetary gear train of wind driven generator.

Factors governing the pH in a heterotrophic, turbid, tidal estuary

Science.gov (United States)

Hofmann, A. F.; Meysman, F. J. R.; Soetaert, K.; Middelburg, J. J.

2009-01-01

A method to quantify the influence of kinetically modelled biogeochemical processes on the pH of an ecosystem with time variable acid-base dissociation constants is presented and applied to the heterotrophic, turbid Scheldt estuary (SW Netherlands, N Belgium). Nitrification is identified as the main process governing the pH profile of this estuary, while CO2 degassing and advective-dispersive transport "buffer" the effect of nitrification. CO2 degassing accounts for the largest proton turnover per year in the whole estuary. There is a clear inverse correlation between oxygen turnover and proton turnover. The main driver of long-term changes in the mean estuarine pH from 2001 to 2004 is a changing freshwater flow which influences the pH "directly" via [∑CO2] and [TA] and to a significant amount also "indirectly" via [∑NH4+] and the nitrification rates in the estuary.

[Resolving excitation emission matrix spectroscopy of estuarine CDOM with parallel factor analysis and its application in organic pollution monitoring].

Science.gov (United States)

Guo, Wei-Dong; Huang, Jian-Ping; Hong, Hua-Sheng; Xu, Jing; Deng, Xun

2010-06-01

The distribution and estuarine behavior of fluorescent components of chromophoric dissolved organic matter (CDOM) from Jiulong Estuary were determined by fluorescence excitation emission matrix spectroscopy (EEMs) combined with parallel factor analysis (PARAFAC). The feasibility of these components as tracers for organic pollution in estuarine environments was also evaluated. Four separate fluorescent components were identified by PARAFAC, including three humic-like components (C1: 240, 310/382 nm; C2: 230, 250, 340/422 nm; C4: 260, 390/482 nm) and one protein-like components (C3: 225, 275/342 nm). These results indicated that UV humic-like peak A area designated by traditional "peak-picking method" was not a single peak but actually a combination of several fluorescent components, and it also had inherent links to so-called marine humic-like peak M or terrestrial humic-like peak C. Component C2 which include peak M decreased with increase of salinity in Jiulong Estuary, demonstrating that peak M can not be thought as the specific indicator of the "marine" humic-like component. Two humic-like components C1 and C2 showed additional behavior in the turbidity maximum region (salinity CDOM may provide a fast in-situ way to monitor the variation of the degree of organic pollution in estuarine environments.

Data driven fault detection and isolation: a wind turbine scenario

Directory of Open Access Journals (Sweden)

Rubén Francisco Manrique Piramanrique

2015-04-01

Full Text Available One of the greatest drawbacks in wind energy generation is the high maintenance cost associated to mechanical faults. This problem becomes more evident in utility scale wind turbines, where the increased size and nominal capacity comes with additional problems associated with structural vibrations and aeroelastic effects in the blades. Due to the increased operation capability, it is imperative to detect system degradation and faults in an efficient manner, maintaining system integrity, reliability and reducing operation costs. This paper presents a comprehensive comparison of four different Fault Detection and Isolation (FDI filters based on “Data Driven” (DD techniques. In order to enhance FDI performance, a multi-level strategy is used where:  the first level detects the occurrence of any given fault (detection, while  the second identifies the source of the fault (isolation. Four different DD classification techniques (namely Support Vector Machines, Artificial Neural Networks, K Nearest Neighbors and Gaussian Mixture Models were studied and compared for each of the proposed classification levels. The best strategy at each level could be selected to build the final data driven FDI system. The performance of the proposed scheme is evaluated on a benchmark model of a commercial wind turbine. 

From DNS to RANS: A Multi-model workflow to understand the Influence of Hurricanes on Generating Turbidity Currents in the Gulf of Mexico

Science.gov (United States)

Syvitski, J. P.; Arango, H.; Harris, C. K.; Meiburg, E. H.; Jenkins, C. J.; Auad, G.; Hutton, E.; Kniskern, T. A.; Radhakrishnan, S.

2016-12-01

A loosely coupled numerical workflow is developed to address land-sea pathways for sediment routing from terrestrial and coastal sources, across the continental shelf and ultimately down the continental slope canyon system of the northern Gulf of Mexico (GOM). Model simulations represent a range of environmental conditions that might lead to the generation of turbidity-currents. The workflow comprises: 1) A simulator for the water and sediment discharged from rivers into the GOM with WMBsedv2 with calibration using USGS and USACE gauged river data; 2) Domain grids and bathymetry (ETOPO2) for the ocean models and realistic seabed sediment texture grids (dbSEABED) for the sediment transport models; 3) A spectral wave action simulator (10 km resolution) (WaveWatch III) driven by GFDL - GFS winds; 4) A simulator for ocean dynamics (ROMS) forced with ECMWF ERA winds; 5) A simulator for seafloor resuspension and transport (CSTMS); 6) Simulators (HurriSlip) of seafloor failure and flow ignition locations for boundary input to a turbidity current model; and 7) A RANS turbidity current model (TURBINS) to route sediment flows down GOM canyons, providing estimates of bottom shear stresses. TURBINS was developed first as a DNS model and then converted to an LES model wherein a dynamic turbulence closure scheme was employed. Like most DNS to LES model comparisons (these being done by the UCSB team), turbulence scaling allowed for higher Re applications but were found still not capable of simulating field scale (GOM continental canyons) environments. The LES model was next converted to a non-hydrostatic RANS model capable of field scale applications but only with a daisy-chain approach to multiple model runs along the simulated canyon floor. These model adaptations allowed the workflow to be tested for the year 1-Oct-2007 to 30-Sep-2008 that included two domain Hurricanes (Ike and Gustav). The RANS-TURBINS employed further boundary simplifications on both sediment erosion and

Wind-driven export of Weddell Sea slope water

Science.gov (United States)

Meijers, A. J. S.; Meredith, M. P.; Abrahamsen, E. P.; Morales Maqueda, M. A.; Jones, D. C.; Naveira Garabato, A. C.

2016-10-01

The export of waters from the Weddell Gyre to lower latitudes is an integral component of the southern subpolar contribution to the three-dimensional oceanic circulation. Here we use more than 20 years of repeat hydrographic data on the continental slope on the northern tip of the Antarctic Peninsula and 5 years of bottom lander data on the slope at 1000 m to show the intermittent presence of a relatively cold, fresh, westward flowing current. This is often bottom-intensified between 600 and 2000 dbar with velocities of over 20 cm s-1, transporting an average of 1.5 ± 1.5 Sv. By comparison with hydrography on the continental slope within the Weddell Sea and modeled tracer release experiments we show that this slope current is an extension of the Antarctic Slope Current that has crossed the South Scotia Ridge west of Orkney Plateau. On monthly to interannual time scales the density of the slope current is negatively correlated (r > 0.6 with a significance of over 95%) with eastward wind stress over the northern Weddell Sea, but lagging it by 6-13 months. This relationship holds in both the high temporal resolution bottom lander time series and the 20+ year annual hydrographic occupations and agrees with Weddell Sea export variability observed further east. We compare several alternative hypotheses for this wind stress/export relationship and find that it is most consistent with wind-driven acceleration of the gyre boundary current, possibly modulated by eddy dynamics, and represents a mechanism by which climatic perturbations can be rapidly transmitted as fluctuations in the supply of intermediate-level waters to lower latitudes.

Wind-driven roof turbines: a novel way to improve ventilation for TB infection control in health facilities.

Directory of Open Access Journals (Sweden)

Helen Cox

Full Text Available OBJECTIVE: Tuberculosis transmission in healthcare facilities contributes significantly to the TB epidemic, particularly in high HIV settings. Although improving ventilation may reduce transmission, there is a lack of evidence to support low-cost practical interventions. We assessed the efficacy of wind-driven roof turbines to achieve recommended ventilation rates, compared to current recommended practices for natural ventilation (opening windows, in primary care clinic rooms in Khayelitsha, South Africa. METHODS: Room ventilation was assessed (CO₂ gas tracer technique in 4 rooms where roof turbines and air-intake grates were installed, across three scenarios: turbine, grate and window closed, only window open, and only turbine and grate open, with concurrent wind speed measurement. 332 measurements were conducted over 24 months. FINDINGS: For all 4 rooms combined, median air changes per hour (ACH increased with wind speed quartiles across all scenarios. Higher median ACH were recorded with open roof turbines and grates, compared to open windows across all wind speed quartiles. Ventilation with open turbine and grate exceeded WHO-recommended levels (60 Litres/second/patient for 95% or more of measurements in 3 of the 4 rooms; 47% in the remaining room, where wind speeds were lower and a smaller diameter turbine was installed. CONCLUSION: High room ventilation rates, meeting recommended thresholds, may be achieved using wind-driven roof turbines and grates, even at low wind speeds. Roof turbines and air-intake grates are not easily closed by staff, allowing continued ventilation through colder periods. This simple, low-cost technology represents an important addition to our tools for TB infection control.

Wind-driven roof turbines: a novel way to improve ventilation for TB infection control in health facilities.

Science.gov (United States)

Cox, Helen; Escombe, Rod; McDermid, Cheryl; Mtshemla, Yolanda; Spelman, Tim; Azevedo, Virginia; London, Leslie

2012-01-01

Tuberculosis transmission in healthcare facilities contributes significantly to the TB epidemic, particularly in high HIV settings. Although improving ventilation may reduce transmission, there is a lack of evidence to support low-cost practical interventions. We assessed the efficacy of wind-driven roof turbines to achieve recommended ventilation rates, compared to current recommended practices for natural ventilation (opening windows), in primary care clinic rooms in Khayelitsha, South Africa. Room ventilation was assessed (CO₂ gas tracer technique) in 4 rooms where roof turbines and air-intake grates were installed, across three scenarios: turbine, grate and window closed, only window open, and only turbine and grate open, with concurrent wind speed measurement. 332 measurements were conducted over 24 months. For all 4 rooms combined, median air changes per hour (ACH) increased with wind speed quartiles across all scenarios. Higher median ACH were recorded with open roof turbines and grates, compared to open windows across all wind speed quartiles. Ventilation with open turbine and grate exceeded WHO-recommended levels (60 Litres/second/patient) for 95% or more of measurements in 3 of the 4 rooms; 47% in the remaining room, where wind speeds were lower and a smaller diameter turbine was installed. High room ventilation rates, meeting recommended thresholds, may be achieved using wind-driven roof turbines and grates, even at low wind speeds. Roof turbines and air-intake grates are not easily closed by staff, allowing continued ventilation through colder periods. This simple, low-cost technology represents an important addition to our tools for TB infection control.

Steady-state analysis of a conceptual offshore wind turbine driven electricity and thermocline energy extraction plant

OpenAIRE

Buhagiar, Daniel; Sant, Tonio

2014-01-01

A system for using offshore wind energy to generate electricity and simultaneously extract thermal energy is proposed. This concept is based on an offshore wind turbine driven hydraulic pump supplying deep seawater under high pressure to a land based plant consisting of a hydroelectric power generation unit and heat exchanger. A steady-state system model is developed using empirical formulae. The mathematical model comprises the fundamental system sub-models that are categoris...

Innovative GOCI algorithm to derive turbidity in highly turbid waters: a case study in the Zhejiang coastal area.

Science.gov (United States)

Qiu, Zhongfeng; Zheng, Lufei; Zhou, Yan; Sun, Deyong; Wang, Shengqiang; Wu, Wei

2015-09-21

An innovative algorithm is developed and validated to estimate the turbidity in Zhejiang coastal area (highly turbid waters) using data from the Geostationary Ocean Color Imager (GOCI). First, satellite-ground synchronous data (n = 850) was collected from 2014 to 2015 using 11 buoys equipped with a Yellow Spring Instrument (YSI) multi-parameter sonde capable of taking hourly turbidity measurements. The GOCI data-derived Rayleigh-corrected reflectance (R(rc)) was used in place of the widely used remote sensing reflectance (R(rs)) to model turbidity. Various band characteristics, including single band, band ratio, band subtraction, and selected band combinations, were analyzed to identify correlations with turbidity. The results indicated that band 6 had the closest relationship to turbidity; however, the combined bands 3 and 6 model simulated turbidity most accurately (R(2) = 0.821, pcoastal waters is feasible. As an example, the developed model was applied to 8 hourly GOCI images on 30 December 2014. Three cross sections were selected to identify the spatiotemporal variation of turbidity in the study area. Turbidity generally decreased from near-shore to offshore and from morning to afternoon. Overall, the findings of this study provide a simple and practical method, based on GOCI data, to estimate turbidity in highly turbid coastal waters at high temporal resolutions.

Monitoring of labile copper and zinc in estuarine waters using cathodic stripping chronopotentiometry

International Nuclear Information System (INIS)

Berg, C.M.G.

1991-01-01

Cathodic stripping chronopotentiometry (CSC) is readily suitable for automation, and sensitivity is often not affected by variations in major ion concentration (salinity) or by the dissolved concentration of oxygen. So this technique is very suitable for automated monitoring of certain trace elements in natural waters, including estuarine waters. The suitability of CSC for monitoring is demonstrated by measuring the concentrations of copper and zinc in the Tamar estuary in-line and automatically. The measuring rate was approximately 90h -1 . The concentrations of zinc and copper in the Tamar estuary were shown to behave in agreement with the findings of previous studies; the labile metal concentrations increased in the turbidity maximum and decreased immediately after it (at higher salinities) as a result of particle scavenging; gradual increase was apparent at intermediate salinities as result of pore-water injection, and the metal concentrations followed a dilution pattern with seawater at high salinities. In-line measurements provided a detailed picture of metal behaviour in this estuary and elucidated local inputs. The sensitivity (down to approximately 5 nM Cu and 6 nM Zn) allows monitoring of copper and zinc at levels common in estuarine and coastal waters, but is insufficient to monitor these metals in uncontaminated seawater. (author). 22 refs.; 4 figs

Wind-driven rain as a boundary condition for HAM simulations: analysis of simplified modelling approaches

DEFF Research Database (Denmark)

Janssen, Hans; Blocken, Bert; Roels, Staf

2007-01-01

While the numerical simulation of moisture transfer inside building components is currently undergoing standardisation, the modelling of the atmospheric boundary conditions has received far less attention. This article analyses the modelling of the wind-driven-rain load on building facades...... though: the full variability with the perpendicular wind speed and horizontal rain intensity should be preserved, where feasible, for improved estimations of the moisture transfer in building components. In the concluding section, it is moreover shown that the dependence of the surface moisture transfer...

Turbidity distribution in the Atlantic Ocean

Science.gov (United States)

Eittreim, S.; Thorndike, E.M.; Sullivan, L.

1976-01-01

The regional coverage of Lamont nephelometer data in the North and South Atlantic can be used to map seawater turbidity at all depths. At the level of the clearest water, in the mid-depth regions, the turbidity distribution primarily reflects the pattern of productivity in the surface waters. This suggests that the 'background' turbidity level in the oceans is largely a function of biogenic fallout. The bottom waters of the western Atlantic generally exhibit large increases in turbidity. The most intense benthic nepheloid layers are in the southwestern Argentine basin and northern North American basin; the lowest bottom water turbidity in the western Atlantic is in the equatorial regions. Both the Argentine and North American basin bottom waters appear to derive their high turbidity largely from local resuspension of terrigenous input in these basins. In contrast to the west, the eastern Atlantic basins show very low turbidities with the exception of three regions: the Mediterranean outflow area, the Cape basin, and the West European basin. ?? 1976.

Extreme fire severity patterns in topographic, convective and wind-driven historical wildfires of Mediterranean pine forests.

Directory of Open Access Journals (Sweden)

Judit Lecina-Diaz

Full Text Available Crown fires associated with extreme fire severity are extremely difficult to control. We have assessed fire severity using differenced Normalized Burn Ratio (dNBR from Landsat imagery in 15 historical wildfires of Pinus halepensis Mill. We have considered a wide range of innovative topographic, fuel and fire behavior variables with the purposes of (1 determining the variables that influence fire severity patterns among fires (considering the 15 wildfires together and (2 ascertaining whether different variables affect extreme fire severity within the three fire types (topographic, convective and wind-driven fires. The among-fires analysis showed that fires in less arid climates and with steeper slopes had more extreme severity. In less arid conditions there was more crown fuel accumulation and closer forest structures, promoting high vertical and horizontal fuel continuity and extreme fire severity. The analyses carried out for each fire separately (within fires showed more extreme fire severity in areas in northern aspects, with steeper slopes, with high crown biomass and in climates with more water availability. In northern aspects solar radiation was lower and fuels had less water limitation to growth which, combined with steeper slopes, produced more extreme severity. In topographic fires there was more extreme severity in northern aspects with steeper slopes and in areas with more water availability and high crown biomass; in convection-dominated fires there was also more extreme fire severity in northern aspects with high biomass; while in wind-driven fires there was only a slight interaction between biomass and water availability. This latter pattern could be related to the fact that wind-driven fires spread with high wind speed, which could have minimized the effect of other variables. In the future, and as a consequence of climate change, new zones with high crown biomass accumulated in non-common drought areas will be available to burn

Extreme fire severity patterns in topographic, convective and wind-driven historical wildfires of Mediterranean pine forests.

Science.gov (United States)

Lecina-Diaz, Judit; Alvarez, Albert; Retana, Javier

2014-01-01

Crown fires associated with extreme fire severity are extremely difficult to control. We have assessed fire severity using differenced Normalized Burn Ratio (dNBR) from Landsat imagery in 15 historical wildfires of Pinus halepensis Mill. We have considered a wide range of innovative topographic, fuel and fire behavior variables with the purposes of (1) determining the variables that influence fire severity patterns among fires (considering the 15 wildfires together) and (2) ascertaining whether different variables affect extreme fire severity within the three fire types (topographic, convective and wind-driven fires). The among-fires analysis showed that fires in less arid climates and with steeper slopes had more extreme severity. In less arid conditions there was more crown fuel accumulation and closer forest structures, promoting high vertical and horizontal fuel continuity and extreme fire severity. The analyses carried out for each fire separately (within fires) showed more extreme fire severity in areas in northern aspects, with steeper slopes, with high crown biomass and in climates with more water availability. In northern aspects solar radiation was lower and fuels had less water limitation to growth which, combined with steeper slopes, produced more extreme severity. In topographic fires there was more extreme severity in northern aspects with steeper slopes and in areas with more water availability and high crown biomass; in convection-dominated fires there was also more extreme fire severity in northern aspects with high biomass; while in wind-driven fires there was only a slight interaction between biomass and water availability. This latter pattern could be related to the fact that wind-driven fires spread with high wind speed, which could have minimized the effect of other variables. In the future, and as a consequence of climate change, new zones with high crown biomass accumulated in non-common drought areas will be available to burn as extreme

Impact of neutrino flavor oscillations on the neutrino-driven wind nucleosynthesis of an electron-capture supernova

NARCIS (Netherlands)

Pllumbi, E.; Tamborra, I.; Wanajo, S.; Janka, H.-T.; Hüdepohl, L.

2015-01-01

Neutrino oscillations, especially to light sterile states, can affect nucleosynthesis yields because of their possible feedback effect on the electron fraction (Ye). For the first time, we perform nucleosynthesis calculations for neutrino-driven wind trajectories from the neutrino-cooling phase of

Development of a Wind Plant Large-Eddy Simulation with Measurement-Driven Atmospheric Inflow

Energy Technology Data Exchange (ETDEWEB)

Quon, Eliot W.; Churchfield, Matthew J.; Cheung, Lawrence; Kern, Stefan

2017-01-09

This paper details the development of an aeroelastic wind plant model with large-eddy simulation (LES). The chosen LES solver is the Simulator for Wind Farm Applications (SOWFA) based on the OpenFOAM framework, coupled to NREL's comprehensive aeroelastic analysis tool, FAST. An atmospheric boundary layer (ABL) precursor simulation was constructed based on assessments of meteorological tower, lidar, and radar data over a 3-hour window. This precursor was tuned to the specific atmospheric conditions that occurred both prior to and during the measurement campaign, enabling capture of a night-to-day transition in the turbulent ABL. In the absence of height-varying temperature measurements, spatially averaged radar data were sufficient to characterize the atmospheric stability of the wind plant in terms of the shear profile, and near-ground temperature sensors provided a reasonable estimate of the ground heating rate describing the morning transition. A full aeroelastic simulation was then performed for a subset of turbines within the wind plant, driven by the precursor. Analysis of two turbines within the array, one directly waked by the other, demonstrated good agreement with measured time-averaged loads.

Wind influence on a coastal buoyant outflow

Science.gov (United States)

Whitney, Michael M.; Garvine, Richard W.

2005-03-01

This paper investigates the interplay between river discharge and winds in forcing coastal buoyant outflows. During light winds a plume influenced by the Earth's rotation will flow down shelf (in the direction of Kelvin wave propagation) as a slender buoyancy-driven coastal current. Downwelling favorable winds augment this down-shelf flow, narrow the plume, and mix the water column. Upwelling favorable winds drive currents that counter the buoyancy-driven flow, spread plume waters offshore, and rapidly mix buoyant waters. Two criteria are developed to assess the wind influence on a buoyant outflow. The wind strength index (Ws) determines whether a plume's along-shelf flow is in a wind-driven or buoyancy-driven state. Ws is the ratio of the wind-driven and buoyancy-driven along-shelf velocities. Wind influence on across-shelf plume structure is rated with a timescale (ttilt) for the isopycnal tilting caused by wind-driven Ekman circulation. These criteria are used to characterize wind influence on the Delaware Coastal Current and can be applied to other coastal buoyant outflows. The Delaware buoyant outflow is simulated for springtime high-river discharge conditions. Simulation results and Ws values reveal that the coastal current is buoyancy-driven most of the time (∣Ws∣ Wind events, however, overwhelm the buoyancy-driven flow (∣Ws∣ > 1) several times during the high-discharge period. Strong upwelling events reverse the buoyant outflow; they constitute an important mechanism for transporting fresh water up shelf. Across-shelf plume structure is more sensitive to wind influence than the along-shelf flow. Values of ttilt indicate that moderate or strong winds persisting throughout a day can modify plume width significantly. Plume widening during upwelling events is accompanied by mixing that can erase the buoyant outflow.

Benthic infaunal community structuring in an acidified tropical estuarine system.

Science.gov (United States)

Hossain, M Belal; Marshall, David J

2014-01-01

chemical properties of the water (pH and salinity). Infaunal estuarine communities, which are typically adapted to survive relatively acidic conditions, may be less exposed, less sensitive, and less vulnerable than epibenthic or pelagic communities to further acidification of above-sediment waters. These data question the extent to which all marine infaunal communities, including oceanic communities, are likely to be affected by future global CO2-driven acidification.

Hindcasting of decadal‐timescale estuarine bathymetric change with a tidal‐timescale model

Science.gov (United States)

Ganju, Neil K.; Schoellhamer, David H.; Jaffe, Bruce E.

2009-01-01

Hindcasting decadal-timescale bathymetric change in estuaries is prone to error due to limited data for initial conditions, boundary forcing, and calibration; computational limitations further hinder efforts. We developed and calibrated a tidal-timescale model to bathymetric change in Suisun Bay, California, over the 1867–1887 period. A general, multiple-timescale calibration ensured robustness over all timescales; two input reduction methods, the morphological hydrograph and the morphological acceleration factor, were applied at the decadal timescale. The model was calibrated to net bathymetric change in the entire basin; average error for bathymetric change over individual depth ranges was 37%. On a model cell-by-cell basis, performance for spatial amplitude correlation was poor over the majority of the domain, though spatial phase correlation was better, with 61% of the domain correctly indicated as erosional or depositional. Poor agreement was likely caused by the specification of initial bed composition, which was unknown during the 1867–1887 period. Cross-sectional bathymetric change between channels and flats, driven primarily by wind wave resuspension, was modeled with higher skill than longitudinal change, which is driven in part by gravitational circulation. The accelerated response of depth may have prevented gravitational circulation from being represented properly. As performance criteria became more stringent in a spatial sense, the error of the model increased. While these methods are useful for estimating basin-scale sedimentation changes, they may not be suitable for predicting specific locations of erosion or deposition. They do, however, provide a foundation for realistic estuarine geomorphic modeling applications.

Enhanced Control for a Direct-driven Permanent Synchronous Generator Wind-power Generation System with Flywheel Energy Storage Unit Under Unbalanced Grid Fault

DEFF Research Database (Denmark)

Yao, Jun; Zhou, Te; Hu, Weihao

2015-01-01

This article presents an enhanced control strategy for a direct-driven permanent synchronous generator based wind-power generation system with a flywheel energy storage unit. The behaviors of the direct-driven permanent magnet synchronous generator system with a flywheel energy storage unit under......, the DC-link voltage oscillations can be effectively suppressed during the unbalanced grid fault by controlling the flywheel energy storage unit. Furthermore, a proportional–integral-resonant controller is designed for the flywheel motor to eliminate the oscillations in the DC-link voltage. Finally......, the proposed coordinated control strategy for the direct-driven permanent magnet synchronous generator system with a flywheel energy storage unit has been validated by the simulation results of a 1-MW direct-driven permanent magnet synchronous generator wind power generation system with a flywheel energy...

Sediment concentrations, flow conditions, and downstream evolution of two turbidity currents, Monterey Canyon, USA

Science.gov (United States)

Xu, Jingping; Octavio E. Sequeiros,; Noble, Marlene A.

2014-01-01

The capacity of turbidity currents to carry sand and coarser sediment from shallow to deep regions in the submarine environment has attracted the attention of researchers from different disciplines. Yet not only are field measurements of oceanic turbidity currents a rare achievement, but also the data that have been collected consist mostly of velocity records with very limited or no suspended sediment concentration or grain size distribution data. This work focuses on two turbidity currents measured in Monterey Canyon in 2002 with emphasis on suspended sediment from unique samples collected within the body of these currents. It is shown that concentration and grain size of the suspended material, primarily controlled by the source of the gravity flows and their interaction with bed material, play a significant role in shaping the characteristics of the turbidity currents as they travel down the canyon. Before the flows reach their normal or quasi-steady state, which is defined by bed slope, bed roughness, and suspended grain size, they might pass through a preliminary adjustment stage where they are subject to capacity-driven deposition, and release heavy material in excess. Flows composed of fine (silt/clay) sediments tend to be thicker than those with sands. The measured velocity and concentration data confirm that flow patterns differ between the front and body of turbidity currents and that, even after reaching normal state, the flow regime can be radically disrupted by abrupt changes in canyon morphology.

Effects of Wind Velocity Driven by Alfven Waves on the Line Profiles for 32 CYG

Directory of Open Access Journals (Sweden)

Kyung-Mee Kim

1996-06-01

Full Text Available We calculate the theoretical line profiles for 32 Cyg in order to investigate the influence of various velocity fields. Line profiles are calculated with wind accelerations driven by Alfven waves and described by velocity parameters. The results for Alfvenic wave model show weakened line profiles. For the orbital phases ¥÷=0.78 and ¥÷=0.06 the Alfvenic models show strong absorption part due to very low densities at the surface of the supergiant. Hence, we conclude the velocity gradient of the wind near the supergiant could influence on the theoretical line formation.

Can Winds Driven by Active Galactic Nuclei Account for the Extragalactic Gamma-Ray and Neutrino Backgrounds?

Science.gov (United States)

Liu, Ruo-Yu; Murase, Kohta; Inoue, Susumu; Ge, Chong; Wang, Xiang-Yu

2018-05-01

Various observations are revealing the widespread occurrence of fast and powerful winds in active galactic nuclei (AGNs) that are distinct from relativistic jets, likely launched from accretion disks and interacting strongly with the gas of their host galaxies. During the interaction, strong shocks are expected to form that can accelerate nonthermal particles to high energies. Such winds have been suggested to be responsible for a large fraction of the observed extragalactic gamma-ray background (EGB) and the diffuse neutrino background, via the decay of neutral and charged pions generated in inelastic pp collisions between protons accelerated by the forward shock and the ambient gas. However, previous studies did not properly account for processes such as adiabatic losses that may reduce the gamma-ray and neutrino fluxes significantly. We evaluate the production of gamma rays and neutrinos by AGN-driven winds in detail by modeling their hydrodynamic and thermal evolution, including the effects of their two-temperature structure. We find that they can only account for less than ∼30% of the EGB flux, as otherwise the model would violate the independent upper limit derived from the diffuse isotropic gamma-ray background. If the neutrino spectral index is steep with Γ ≳ 2.2, a severe tension with the isotropic gamma-ray background would arise as long as the winds contribute more than 20% of the IceCube neutrino flux in the 10–100 TeV range. At energies ≳ 100 TeV, we find that the IceCube neutrino flux may still be accountable by AGN-driven winds if the spectral index is as small as Γ ∼ 2.0–2.1.

Turbidity Currents With Equilibrium Basal Driving Layers: A Mechanism for Long Runout

Science.gov (United States)

Luchi, R.; Balachandar, S.; Seminara, G.; Parker, G.

2018-02-01

Turbidity currents run out over 100 km in lakes and reservoirs, and over 1,000 km in the ocean. They do so without dissipating themselves via excess entrainment of ambient water. Existing layer-averaged formulations cannot capture this. We use a numerical model to describe the temporal evolution of a turbidity current toward steady state under condition of zero net sediment flux at the bed. The flow self-partitions itself into two layers. The lower "driving layer" approaches an invariant flow thickness, velocity profile, and suspended sediment concentration profile that sequesters nearly all of the suspended sediment. This layer can continue indefinitely at steady state over a constant bed slope. The upper "driven layer" contains a small fraction of the suspended sediment. The devolution of the flow into these two layers likely allows the driving layer to run out long distances.

Some results of turbidity networks

OpenAIRE

Volz, F. E.

2011-01-01

Turbidity networks to obtain daily values of haze attenuation from measurements of solar radiation, mostly by means of sun photometers, were established in 1961 in the USA by the National Center for Air Pollution Control, Cincinnati, Ohio, and in Western Europe from 1963 to 1967 by the author. The course of turbidity in the two networks during interesting periods is presented. Discussion of synoptic variations of turbidity is rather difficult, when referring to periods of rapid change of air ...

Protein aggregate turbidity: Simulation of turbidity profiles for mixed-aggregation reactions.

Science.gov (United States)

Hall, Damien; Zhao, Ran; Dehlsen, Ian; Bloomfield, Nathaniel; Williams, Steven R; Arisaka, Fumio; Goto, Yuji; Carver, John A

2016-04-01

Due to their colloidal nature, all protein aggregates scatter light in the visible wavelength region when formed in aqueous solution. This phenomenon makes solution turbidity, a quantity proportional to the relative loss in forward intensity of scattered light, a convenient method for monitoring protein aggregation in biochemical assays. Although turbidity is often taken to be a linear descriptor of the progress of aggregation reactions, this assumption is usually made without performing the necessary checks to provide it with a firm underlying basis. In this article, we outline utilitarian methods for simulating the turbidity generated by homogeneous and mixed-protein aggregation reactions containing fibrous, amorphous, and crystalline structures. The approach is based on a combination of Rayleigh-Gans-Debye theory and approximate forms of the Mie scattering equations. Crown Copyright © 2015. Published by Elsevier Inc. All rights reserved.

Data-Driven Method for Wind Turbine Yaw Angle Sensor Zero-Point Shifting Fault Detection

Directory of Open Access Journals (Sweden)

Yan Pei

2018-03-01

Full Text Available Wind turbine yaw control plays an important role in increasing the wind turbine production and also in protecting the wind turbine. Accurate measurement of yaw angle is the basis of an effective wind turbine yaw controller. The accuracy of yaw angle measurement is affected significantly by the problem of zero-point shifting. Hence, it is essential to evaluate the zero-point shifting error on wind turbines on-line in order to improve the reliability of yaw angle measurement in real time. Particularly, qualitative evaluation of the zero-point shifting error could be useful for wind farm operators to realize prompt and cost-effective maintenance on yaw angle sensors. In the aim of qualitatively evaluating the zero-point shifting error, the yaw angle sensor zero-point shifting fault is firstly defined in this paper. A data-driven method is then proposed to detect the zero-point shifting fault based on Supervisory Control and Data Acquisition (SCADA data. The zero-point shifting fault is detected in the proposed method by analyzing the power performance under different yaw angles. The SCADA data are partitioned into different bins according to both wind speed and yaw angle in order to deeply evaluate the power performance. An indicator is proposed in this method for power performance evaluation under each yaw angle. The yaw angle with the largest indicator is considered as the yaw angle measurement error in our work. A zero-point shifting fault would trigger an alarm if the error is larger than a predefined threshold. Case studies from several actual wind farms proved the effectiveness of the proposed method in detecting zero-point shifting fault and also in improving the wind turbine performance. Results of the proposed method could be useful for wind farm operators to realize prompt adjustment if there exists a large error of yaw angle measurement.

A Hybrid Genetic Wind Driven Heuristic Optimization Algorithm for Demand Side Management in Smart Grid

Directory of Open Access Journals (Sweden)

Nadeem Javaid

2017-03-01

Full Text Available In recent years, demand side management (DSM techniques have been designed for residential, industrial and commercial sectors. These techniques are very effective in flattening the load profile of customers in grid area networks. In this paper, a heuristic algorithms-based energy management controller is designed for a residential area in a smart grid. In essence, five heuristic algorithms (the genetic algorithm (GA, the binary particle swarm optimization (BPSO algorithm, the bacterial foraging optimization algorithm (BFOA, the wind-driven optimization (WDO algorithm and our proposed hybrid genetic wind-driven (GWD algorithm are evaluated. These algorithms are used for scheduling residential loads between peak hours (PHs and off-peak hours (OPHs in a real-time pricing (RTP environment while maximizing user comfort (UC and minimizing both electricity cost and the peak to average ratio (PAR. Moreover, these algorithms are tested in two scenarios: (i scheduling the load of a single home and (ii scheduling the load of multiple homes. Simulation results show that our proposed hybrid GWD algorithm performs better than the other heuristic algorithms in terms of the selected performance metrics.

Application of a colorimeter for turbidity measurement

Science.gov (United States)

Wen, Yizhang; Hu, Yingtian; Wang, Xiaoping

2016-02-01

This paper describes a new turbidity transducer based on color measurement. The absorbance of solutions reflects the absorption and scattering of suspended particle for incident light which could determine the turbidity of solutions. The experimental results indicate that there are good linear relationships between chromaticity and turbidity. The new way is suitable for continuous monitoring of water turbidity in the wide range.

Application of a colorimeter for turbidity measurement

International Nuclear Information System (INIS)

Wen, Yizhang; Hu, Yingtian; Wang, Xiaoping

2016-01-01

This paper describes a new turbidity transducer based on color measurement. The absorbance of solutions reflects the absorption and scattering of suspended particle for incident light which could determine the turbidity of solutions. The experimental results indicate that there are good linear relationships between chromaticity and turbidity. The new way is suitable for continuous monitoring of water turbidity in the wide range. (paper)

Turbidity in extreme western Lake Superior. [contamination of Duluth, Minnesota water intake

Science.gov (United States)

Sydor, M.

1975-01-01

Data were obtained from ERTS images for western Lake Superior for 1972-74. Data examination showed that for easterly winds the turbidity originating along the Wisconsin shore and the resuspension areas are transported northward then out along a N.E. path where it disperses, and often, for large storms, contaminates the Duluth water intake. Contaminants such as dredging fines anywhere along these paths would likewise find their way to the intake areas in concentrations comparable to the relative red clay concentration.

Star Formation-Driven Winds in the Early Universe

Science.gov (United States)

Peek, Matthew; Lundgren, Britt; Brammer, Gabriel

2018-01-01

Measuring the extent of star formation-driven winds from galaxies in the early universe is crucial for understanding of how galaxies evolve over cosmic time. Using WFC3/IR grism data from the Hubble Space Telescope (HST), we have measured the star formation rates and star formation rate surface densities of several hundred galaxies at redshift (z) = 1, when the universe was roughly half its present age. The galaxies we examine are also probed by background quasars, whose spectra provide information about the extent of metal-enriched gas in their halos. We use a computational pipeline to measure the density of the star formation in each galaxy and correlate these measurements with detections of Mg II absorption in nearby quasar spectra from the Sloan Digital Sky Survey. Our preliminary results support a model in which galaxies with high SFR surface densities drive metal-enriched gas out of the disk and into these galaxies’ extended halos, where that gas is detected in the spectra of more distant quasars.

Development of a Wind Plant Large-Eddy Simulation with Measurement-Driven Atmospheric Inflow: Preprint

Energy Technology Data Exchange (ETDEWEB)

Quon, Eliot; Churchfield, Matthew; Cheung, Lawrence; Kern, Stefan

2017-02-01

This paper details the development of an aeroelastic wind plant model with large-eddy simulation (LES). The chosen LES solver is the Simulator for Wind Farm Applications (SOWFA) based on the OpenFOAM framework, coupled to NREL's comprehensive aeroelastic analysis tool, FAST. An atmospheric boundary layer (ABL) precursor simulation was constructed based on assessments of meteorological tower, lidar, and radar data over a 3-hour window. This precursor was tuned to the specific atmospheric conditions that occurred both prior to and during the measurement campaign, enabling capture of a night-to-day transition in the turbulent ABL. In the absence of height-varying temperature measurements, spatially averaged radar data were sufficient to characterize the atmospheric stability of the wind plant in terms of the shear profile, and near-ground temperature sensors provided a reasonable estimate of the ground heating rate describing the morning transition. A full aeroelastic simulation was then performed for a subset of turbines within the wind plant, driven by the precursor. Analysis of two turbines within the array, one directly waked by the other, demonstrated good agreement with measured time-averaged loads.

Suspended-sediment flux and retention in a backwater tidal slough complex near the landward boundary of an estuary

Science.gov (United States)

Morgan-King, Tara L.; Schoellhamer, David H.

2013-01-01

Backwater tidal sloughs are commonly found at the landward boundary of estuaries. The Cache Slough complex is a backwater tidal region within the Upper Sacramento–San Joaquin Delta that includes two features that are relevant for resource managers: (1) relatively high abundance of the endangered fish, delta smelt (Hypomesus transpacificus), which prefers turbid water and (2) a recently flooded shallow island, Liberty Island, that is a prototype for habitat restoration. We characterized the turbidity around Liberty Island by measuring suspended-sediment flux at four locations from July 2008 through December 2010. An estuarine turbidity maximum in the backwater Cache Slough complex is created by tidal asymmetry, a limited tidal excursion, and wind-wave resuspension. During the study, there was a net export of sediment, though sediment accumulates within the region from landward tidal transport during the dry season. Sediment is continually resuspended by both wind waves and flood tide currents. The suspended-sediment mass oscillates within the region until winter freshwater flow pulses flush it seaward. The hydrodynamic characteristics within the backwater region such as low freshwater flow during the dry season, flood tide dominance, and a limited tidal excursion favor sediment retention.

Journal of Earth System Science | Indian Academy of Sciences

Indian Academy of Sciences (India)

The strong NW and SW winds (3.2–3.7ms−1) and wind-driven waves and currents seem to have acted effectively at the mouth of the estuary in developing turbidity maximum. The impact of sea breeze appears nearly same as that of trade winds and cannot be underestimated in sediment resuspension and deposition.

RECONNECTION-DRIVEN CORONAL-HOLE JETS WITH GRAVITY AND SOLAR WIND

Energy Technology Data Exchange (ETDEWEB)

Karpen, J. T.; DeVore, C. R.; Antiochos, S. K. [Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt MD 20771 (United States); Pariat, E. [LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, UPMC Univ. Paris 06, Univ. Paris Diderot, Sorbonne Paris Cité, 5 place Jules Janssen, F-92195 Meudon (France)

2017-01-01

Coronal-hole jets occur ubiquitously in the Sun's coronal holes, at EUV and X-ray bright points associated with intrusions of minority magnetic polarity. The embedded-bipole model for these jets posits that they are driven by explosive, fast reconnection between the stressed closed field of the embedded bipole and the open field of the surrounding coronal hole. Previous numerical studies in Cartesian geometry, assuming uniform ambient magnetic field and plasma while neglecting gravity and solar wind, demonstrated that the model is robust and can produce jet-like events in simple configurations. We have extended these investigations by including spherical geometry, gravity, and solar wind in a nonuniform, coronal hole-like ambient atmosphere. Our simulations confirm that the jet is initiated by the onset of a kink-like instability of the internal closed field, which induces a burst of reconnection between the closed and external open field, launching a helical jet. Our new results demonstrate that the jet propagation is sustained through the outer corona, in the form of a traveling nonlinear Alfvén wave front trailed by slower-moving plasma density enhancements that are compressed and accelerated by the wave. This finding agrees well with observations of white-light coronal-hole jets, and can explain microstreams and torsional Alfvén waves detected in situ in the solar wind. We also use our numerical results to deduce scaling relationships between properties of the coronal source region and the characteristics of the resulting jet, which can be tested against observations.

Influence of input data on airflow network accuracy in residential buildings with natural wind- and stack-driven ventilation

Institute of Scientific and Technical Information of China (English)

Krzysztof Arendt; Marek Krzaczek; Jacek Tejchman

2017-01-01

The airflow network (AFN) modeling approach provides an attractive balance between the accuracy and computational demand for naturally ventilated buildings. Its accuracy depends on input parameters such as wind pressure and opening discharge coefficients. In most cases, these parameters are obtained from secondary sources which are solely representative for very simplified buildings, i.e. for buildings without facade details. Although studies comparing wind pressure coefficients or discharge coefficients from different sources exist, the knowledge regarding the effect of input data on AFN is still poor. In this paper, the influence of wind pressure data on the accuracy of a coupled AFN-BES model for a real building with natural wind- and stack-driven ventilation was analyzed. The results of 8 computation cases with different wind pressure data from secondary sources were compared with the measured data. Both the indoor temperatures and the airflow were taken into account. The outcomes indicated that the source of wind pressure data had a significant influence on the model performance.

Simulation of barotropic wind-driven circulation in the upper layers of Bay of Bengal and Andaman Sea during the southwest and northeast monsoon seasons using observed winds

Digital Repository Service at National Institute of Oceanography (India)

Bahulayan, N.; Unnikrishnan, A.S.

A two-dimensional, nonlinear, vertically integrated model was used to simulate depth-mean wind-driven circulation in the upper Ekman layers of the Bay of Bengal and Andaman Sea. The model resolution was one third of a degree in the latitude...

Strong links between metal contamination, habitat modification and estuarine larval fish distributions

Energy Technology Data Exchange (ETDEWEB)

McKinley, Andrew C., E-mail: andrew.mckinley@hotmail.com [Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales 2052 (Australia); Miskiewicz, Anthony [Environment and Recreation, Wollongong City Council, 41 Burelli Street, Wollongong, New South Wales 2500 (Australia); Taylor, Matthew D.; Johnston, Emma L. [Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales 2052 (Australia)

2011-06-15

Changes to larval fish assemblages may have far reaching ecological impacts. Correlations between habitat modification, contamination and marine larval fish communities have rarely been assessed in situ. We investigated links between the large-scale distribution of stressors and larval fish assemblages in estuarine environments. Larval fish communities were sampled using a benthic sled within the inner and outer zones of three heavily modified and three relatively unmodified estuaries. Larval abundances were significantly greater in modified estuaries, and there were trends towards greater diversity in these systems. Differences in larval community composition were strongly related to sediment metal levels and reduced seagrass cover. The differences observed were driven by two abundant species, Paedogobius kimurai and Ambassis jacksoniensis, which occurred in large numbers almost exclusively in highly contaminated and pristine locations respectively. These findings suggest that contamination and habitat alteration manifest in substantial differences in the composition of estuarine larval fish assemblages. - Highlights: > We examine contamination/habitat modification impacts on larval fish. > Larvae communities differ between modified/unmodified estuaries. > Larvae are more abundant/diverse in modified areas. > Trends are strongly related to sediment metals/seagrass cover. > Larval impacts have wider ecological importance. - We describe strong links between sediment metals contamination, habitat modification and substantial differences in the composition of the estuarine larval fish assemblage.

Unusual behaviour of phototrophic picoplankton in turbid waters.

Science.gov (United States)

Somogyi, Boglárka; Pálffy, Károly; V-Balogh, Katalin; Botta-Dukát, Zoltán; Vörös, Lajos

2017-01-01

Autotrophic picoplankton (APP) abundance and contribution to phytoplankton biomass was studied in Hungarian shallow lakes to test the effect of inorganic turbidity determining the size distribution of the phytoplankton. The studied lakes displayed wide turbidity (TSS: 4-2250 mg l-1) and phytoplankton biomass (chlorophyll a: 1-460 μg l-1) range, as well as APP abundance (0 and 100 million cells ml-1) and contribution (0-100%) to total phytoplankton biomass. Inorganic turbidity had a significant effect on the abundance and contribution of APP, resulting in higher values compared to other freshwater lakes with the same phytoplankton biomass. Our analysis has provided empirical evidence for a switching point (50 mg l-1 inorganic turbidity), above which turbidity is the key factor causing APP predominance regardless of phytoplankton biomass in shallow turbid lakes. Our results have shown that turbid shallow lakes are unique waters, where the formerly and widely accepted model (decreasing APP contribution with increasing phytoplankton biomass) is not applicable. We hypothesize that this unusual behaviour of APP in turbid waters is a result of either diminished underwater light intensity or a reduced grazing pressure due to high inorganic turbidity.

Unusual behaviour of phototrophic picoplankton in turbid waters.

Directory of Open Access Journals (Sweden)

Boglárka Somogyi

Full Text Available Autotrophic picoplankton (APP abundance and contribution to phytoplankton biomass was studied in Hungarian shallow lakes to test the effect of inorganic turbidity determining the size distribution of the phytoplankton. The studied lakes displayed wide turbidity (TSS: 4-2250 mg l-1 and phytoplankton biomass (chlorophyll a: 1-460 μg l-1 range, as well as APP abundance (0 and 100 million cells ml-1 and contribution (0-100% to total phytoplankton biomass. Inorganic turbidity had a significant effect on the abundance and contribution of APP, resulting in higher values compared to other freshwater lakes with the same phytoplankton biomass. Our analysis has provided empirical evidence for a switching point (50 mg l-1 inorganic turbidity, above which turbidity is the key factor causing APP predominance regardless of phytoplankton biomass in shallow turbid lakes. Our results have shown that turbid shallow lakes are unique waters, where the formerly and widely accepted model (decreasing APP contribution with increasing phytoplankton biomass is not applicable. We hypothesize that this unusual behaviour of APP in turbid waters is a result of either diminished underwater light intensity or a reduced grazing pressure due to high inorganic turbidity.

Wind Turbine Technologies

DEFF Research Database (Denmark)

Hansen, Anca Daniela

2017-01-01

, and with or without gearboxes, using the latest in power electronics, aerodynamics, and mechanical drive train designs [4]. The main differences between all wind turbine concepts developed over the years, concern their electrical design and control. Today, the wind turbines on the market mix and match a variety......, the design of wind turbines has changed from being convention driven to being optimized driven within the operating regime and market environment. Wind turbine designs have progressed from fixed speed, passive controlled and with drive trains with gearboxes, to become variable speed, active controlled......,6] and to implement modern control system strategies....

Scaling Relations of Starburst-driven Galactic Winds

International Nuclear Information System (INIS)

Tanner, Ryan; Cecil, Gerald; Heitsch, Fabian

2017-01-01

Using synthetic absorption lines generated from 3D hydrodynamical simulations, we explore how the velocity of a starburst-driven galactic wind correlates with the star formation rate (SFR) and SFR density. We find strong correlations for neutral and low ionized gas, but no correlation for highly ionized gas. The correlations for neutral and low ionized gas only hold for SFRs below a critical limit set by the mass loading of the starburst, above which point the scaling relations flatten abruptly. Below this point the scaling relations depend on the temperature regime being probed by the absorption line, not on the mass loading. The exact scaling relation depends on whether the maximum or mean velocity of the absorption line is used. We find that the outflow velocity of neutral gas can be up to five times lower than the average velocity of ionized gas, with the velocity difference increasing for higher ionization states. Furthermore, the velocity difference depends on both the SFR and mass loading of the starburst. Thus, absorption lines of neutral or low ionized gas cannot easily be used as a proxy for the outflow velocity of the hot gas.

Scaling Relations of Starburst-driven Galactic Winds

Energy Technology Data Exchange (ETDEWEB)

Tanner, Ryan [Department of Chemistry and Physics, Augusta University, Augusta, GA 30912 (United States); Cecil, Gerald; Heitsch, Fabian, E-mail: rytanner@augusta.edu [Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3255 (United States)

2017-07-10

Using synthetic absorption lines generated from 3D hydrodynamical simulations, we explore how the velocity of a starburst-driven galactic wind correlates with the star formation rate (SFR) and SFR density. We find strong correlations for neutral and low ionized gas, but no correlation for highly ionized gas. The correlations for neutral and low ionized gas only hold for SFRs below a critical limit set by the mass loading of the starburst, above which point the scaling relations flatten abruptly. Below this point the scaling relations depend on the temperature regime being probed by the absorption line, not on the mass loading. The exact scaling relation depends on whether the maximum or mean velocity of the absorption line is used. We find that the outflow velocity of neutral gas can be up to five times lower than the average velocity of ionized gas, with the velocity difference increasing for higher ionization states. Furthermore, the velocity difference depends on both the SFR and mass loading of the starburst. Thus, absorption lines of neutral or low ionized gas cannot easily be used as a proxy for the outflow velocity of the hot gas.

Formation of intrathermocline eddies at ocean fronts by wind-driven destruction of potential vorticity

Science.gov (United States)

Thomas, Leif N.

2008-08-01

A mechanism for the generation of intrathermocline eddies (ITEs) at wind-forced fronts is examined using a high resolution numerical simulation. Favorable conditions for ITE formation result at fronts forced by "down-front" winds, i.e. winds blowing in the direction of the frontal jet. Down-front winds exert frictional forces that reduce the potential vorticity (PV) within the surface boundary in the frontal outcrop, providing a source for the low-PV water that is the materia prima of ITEs. Meandering of the front drives vertical motions that subduct the low-PV water into the pycnocline, pooling it into the coherent anticyclonic vortex of a submesoscale ITE. As the fluid is subducted along the outcropping frontal isopycnal, the low-PV water, which at the surface is associated with strongly baroclinic flow, re-expresses itself as water with nearly zero absolute vorticity. This generation of strong anticyclonic vorticity results from the tilting of the horizontal vorticity of the frontal jet, not from vortex squashing. During the formation of the ITE, high-PV water from the pycnocline is upwelled alongside the subducting low-PV surface water. The positive correlation between the ITE's velocity and PV fields results in an upward, along-isopycnal eddy PV flux that scales with the surface frictional PV flux driven by the wind. The relationship between the eddy and wind-induced frictional PV flux is nonlocal in time, as the eddy PV flux persists long after the wind forcing is shut off. The ITE's PV flux affects the large-scale flow by driving an eddy-induced transport or bolus velocity down the outcropping isopycnal layer with a magnitude that scales with the Ekman velocity.

Recent Successes of Wave/Turbulence Driven Models of Solar Wind Acceleration

Science.gov (United States)

Cranmer, S. R.; Hollweg, J. V.; Chandran, B. D.; van Ballegooijen, A. A.

2010-12-01

A key obstacle in the way of producing realistic simulations of the Sun-heliosphere system is the lack of a first-principles understanding of coronal heating. Also, it is still unknown whether the solar wind is "fed" through flux tubes that remain open (and are energized by footpoint-driven wavelike fluctuations) or if mass and energy are input intermittently from closed loops into the open-field regions. In this presentation, we discuss self-consistent models that assume the energy comes from solar Alfven waves that are partially reflected, and then dissipated, by magnetohydrodynamic turbulence. These models have been found to reproduce many of the observed features of the fast and slow solar wind without the need for artificial "coronal heating functions" used by earlier models. For example, the models predict a variation with wind speed in commonly measured ratios of charge states and elemental abundances that agrees with observed trends. This contradicts a commonly held assertion that these ratios can only be produced by the injection of plasma from closed-field regions on the Sun. This presentation also reviews two recent comparisons between the models and empirical measurements: (1) The models successfully predict the amplitude and radial dependence of Faraday rotation fluctuations (FRFs) measured by the Helios probes for heliocentric distances between 2 and 15 solar radii. The FRFs are a particularly sensitive test of turbulence models because they depend not only on the plasma density and Alfven wave amplitude in the corona, but also on the turbulent correlation length. (2) The models predict the correct sense and magnitude of changes seen in the polar high-speed solar wind by Ulysses from the previous solar minimum (1996-1997) to the more recent peculiar minimum (2008-2009). By changing only the magnetic field along the polar magnetic flux tube, consistent with solar and heliospheric observations at the two epochs, the model correctly predicts that the

Loss evaluation and design optimisation for direct driven permanent magnet synchronous generators for wind power

Energy Technology Data Exchange (ETDEWEB)

Eriksson, Sandra; Bernhoff, Hans [Swedish Centre for Renewable Electric Energy Conversion, Division for Electricity, Department of Engineering Sciences, Uppsala University, Box 534, 751 21 Uppsala (Sweden)

2011-01-15

When designing a generator for a wind turbine it is important to adapt the generator to the source, i.e. the wind conditions at the specific site. Furthermore, the variable speed operation of the generator needs to be considered. In this paper, electromagnetic losses in direct driven permanent magnet synchronous generators are evaluated through simulations. Six different generators are compared to each other. The simulations are performed by using an electromagnetic model, solved in a finite element environment and a control model developed in MATLAB. It is shown that when designing a generator it is important to consider the statistical wind distribution, control system, and aerodynamic efficiency in order to evaluate the performance properly. In this paper, generators with high overload capability are studied since they are of interest for this specific application. It is shown that a generator optimised for a minimum of losses will have a high overload capability. (author)

COS-burst: Observations of the Impact of Starburst-driven Winds on the Properties of the Circum-galactic Medium

Energy Technology Data Exchange (ETDEWEB)

Heckman, Timothy; Borthakur, Sanchayeeta [Center for Astrophysical Sciences, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Wild, Vivienne [School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9AJ (United Kingdom); Schiminovich, David [Department of Astronomy, Columbia University, New York, NY 10027 (United States); Bordoloi, Rongmon, E-mail: theckma1@jhu.edu [MIT-Kavli Center for Astrophysics and Space Research, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States)

2017-09-10

We report on observations made with the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope ( HST ) using background quasi-stellar objects to probe the circum-galactic medium (CGM) around 17 low-redshift galaxies that are undergoing or have recently undergone a strong starburst (the COS-Burst program). The sightlines extend out to roughly the virial radius of the galaxy halo. We construct control samples of normal star-forming low-redshift galaxies from the COS/ HST archive that match the starbursts in terms of galaxy stellar mass and impact parameter. We find clear evidence that the CGM around the starbursts differs systematically compared to the control galaxies. The Ly α , Si iii, C iv, and possibly O vi absorption lines are stronger as a function of impact parameter, and the ratios of the equivalent widths of C iv/Ly α and Si iii/Ly α are both higher than in normal star-forming galaxies. We also find that the widths and the velocity offsets (relative to v {sub sys}) of the Ly α absorption lines are significantly larger in the CGM of the starbursts, implying velocities of the absorbing material that are roughly twice the halo virial velocity. We show that these properties can be understood as a consequence of the interaction between a starburst-driven wind and the preexisting CGM. These results underscore the importance of winds driven from intensely star-forming galaxies in helping drive the evolution of galaxies and the intergalactic medium. They also offer a new probe of the properties of starburst-driven winds and of the CGM itself.

Establishment of turbidity forecasting model and early-warning system for source water turbidity management using back-propagation artificial neural network algorithm and probability analysis.

Science.gov (United States)

Yang, Tsung-Ming; Fan, Shu-Kai; Fan, Chihhao; Hsu, Nien-Sheng

2014-08-01

The purpose of this study is to establish a turbidity forecasting model as well as an early-warning system for turbidity management using rainfall records as the input variables. The Taipei Water Source Domain was employed as the study area, and ANOVA analysis showed that the accumulative rainfall records of 1-day Ping-lin, 2-day Ping-lin, 2-day Fei-tsui, 2-day Shi-san-gu, 2-day Tai-pin and 2-day Tong-hou were the six most significant parameters for downstream turbidity development. The artificial neural network model was developed and proven capable of predicting the turbidity concentration in the investigated catchment downstream area. The observed and model-calculated turbidity data were applied to developing the turbidity early-warning system. Using a previously determined turbidity as the threshold, the rainfall criterion, above which the downstream turbidity would possibly exceed this respective threshold turbidity, for the investigated rain gauge stations was determined. An exemplary illustration demonstrated the effectiveness of the proposed turbidity early-warning system as a precautionary alarm of possible significant increase of downstream turbidity. This study is the first report of the establishment of the turbidity early-warning system. Hopefully, this system can be applied to source water turbidity forecasting during storm events and provide a useful reference for subsequent adjustment of drinking water treatment operation.

Contribution to the study of the wind and solar radiation over Guadeloupe

International Nuclear Information System (INIS)

Bertin, A.; Frangi, J.P.

2013-01-01

Highlights: • We study wind and solar resource in Guadeloupe (FWI). • Weibull distributions reveal a nocturnal radiative layer blocking wind at airport. • We provide monthly and annual irradiations, horizontal and tilted, for four sites. • Five Linke turbidity coefficient calculation methods are reviewed and compared. - Abstract: Guadeloupean archipelago must reach energy autonomy in 2030 and include at least 50% of renewables in 2020, where wind and photovoltaics can play a significant role. Still, Guadeloupe gathers a lot of landscapes having great impact on wind and solar resource. Study of three 10-years database and one 5-year database locates a nocturnal radiative layer above the airport meteorological station, drastically limiting the wind potential there, and gives all the irradiation components (monthly sums) and therefore key parameters for photovoltaic energy yield. This paper also points out the underestimation of Linke turbidity coefficient in the airport station with Solar Radiation Database (SoDa), compared to ground-based determination, and calculates the value of this coefficient for three stations across Guadeloupe. All those parameters are discussed, as being of importance to make fair predictions of statistical relationships involving preliminary assessment and modeling of wind and solar energy systems. These results can then be used in neighboring countries, Guadeloupe having various meteorological conditions retrieved in Caribbean

40 CFR 141.13 - Maximum contaminant levels for turbidity.

Science.gov (United States)

2010-07-01

... turbidity. 141.13 Section 141.13 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) WATER... Maximum contaminant levels for turbidity. The maximum contaminant levels for turbidity are applicable to... part. The maximum contaminant levels for turbidity in drinking water, measured at a representative...

Thermal and Driven Stochastic Growth of Langmuir Waves in the Solar Wind and Earth's Foreshock

Science.gov (United States)

Cairns, Iver H.; Robinson, P. A.; Anderson, R. R.

2000-01-01

Statistical distributions of Langmuir wave fields in the solar wind and the edge of Earth's foreshock are analyzed and compared with predictions for stochastic growth theory (SGT). SGT quantitatively explains the solar wind, edge, and deep foreshock data as pure thermal waves, driven thermal waves subject to net linear growth and stochastic effects, and as waves in a pure SGT state, respectively, plus radiation near the plasma frequency f(sub p). These changes are interpreted in terms of spatial variations in the beam instability's growth rate and evolution toward a pure SGT state. SGT analyses of field distributions are shown to provide a viable alternative to thermal noise spectroscopy for wave instruments with coarse frequency resolution, and to separate f(sub p) radiation from Langmuir waves.

Application of MODIS Products to Infer Possible Relationships Between Basin Land Cover and Coastal Waters Turbidity Using the Magdalena River, Colombia, as a Case Study

Science.gov (United States)

Madrinan, Max Jacobo Moreno; Cordova, Africa Flores; Olivares, Francisco Delgado; Irwin, Dan

2012-01-01

Basin development and consequent change in basin land cover have been often associated with an increased turbidity in coastal waters because of sediment yield and nutrients loading. The later leads to phytoplankton abundance further exacerbating water turbidity. This subsequently affects biological and physical processes in coastal estuaries by interfering with sun light penetration to coral reefs and sea grass, and even affecting public health. Therefore, consistent estimation of land cover changes and turbidity trend lines is crucial to design environmental and restoration management plans, to predict fate of possible pollutants, and to estimate sedimentary fluxes into the ocean. Ground solely methods to estimate land cover change would be unpractical and traditional methods of monitoring in situ water turbidity can be very expensive and time consuming. Accurate monitoring on the status and trends of basin land cover as well as the water quality of the receiving water bodies are required for analysis of relationships between the two variables. Use of remote sensing (RS) technology provides a great benefit for both fields of study, facilitating monitoring of changes in a timely and cost effective manner and covering wide areas with long term measurements. In this study, the Magdalena River basin and fixed geographical locations in the estuarine waters of its delta are used as a case to study the temporal trend lines of both, land cover change and the reflectance of the water turbidity using satellite technology. Land cover data from a combined product between sensors Terra and Aqua (MCD12Q1) from MODIS will be adapted to the conditions in the Magdalena basin to estimate changes in land cover since year 2000 to 2009. Surface reflectance data from a MODIS, Terra (MOD09GQ), band 1, will be used in lieu of in situ water turbidity for the time period between 2000 and present. Results will be compared with available existing data.

Benthic and pelagic pathways of methylmercury bioaccumulation in estuarine food webs of the northeast United States.

Directory of Open Access Journals (Sweden)

Celia Y Chen

Full Text Available Methylmercury (MeHg is a contaminant of global concern that bioaccumulates and bioamagnifies in marine food webs. Lower trophic level fauna are important conduits of MeHg from sediment and water to estuarine and coastal fish harvested for human consumption. However, the sources and pathways of MeHg to these coastal fisheries are poorly known particularly the potential for transfer of MeHg from the sediment to biotic compartments. Across a broad gradient of human land impacts, we analyzed MeHg concentrations in food webs at ten estuarine sites in the Northeast US (from the Hackensack Meadowlands, NJ to the Gulf of Maine. MeHg concentrations in water column particulate material, but not in sediments, were predictive of MeHg concentrations in fish (killifish and Atlantic silversides. Moreover, MeHg concentrations were higher in pelagic fauna than in benthic-feeding fauna suggesting that MeHg delivery to the water column from methylation sites from within or outside of the estuary may be an important driver of MeHg bioaccumulation in estuarine pelagic food webs. In contrast, bulk sediment MeHg concentrations were only predictive of concentrations of MeHg in the infaunal worms. Our results across a broad gradient of sites demonstrate that the pathways of MeHg to lower trophic level estuarine organisms are distinctly different between benthic deposit feeders and forage fish. Thus, even in systems with contaminated sediments, transfer of MeHg into estuarine food webs maybe driven more by the efficiency of processes that determine MeHg input and bioavailability in the water column.

Nonspherical Radiation Driven Wind Models Applied to Be Stars

Science.gov (United States)

Arauxo, F. X.

1990-11-01

ABSTRACT. In this work we present a model for the structure of a radiatively driven wind in the meridional plane of a hot star. Rotation effects and simulation of viscous forces were included in the motion equations. The line radiation force is considered with the inclusion of the finite disk correction in self-consistent computations which also contain gravity darkening as well as distortion of the star by rotation. An application to a typical BlV star leads to mass-flux ratios between equator and pole of the order of 10 and mass loss rates in the range 5.l0 to Mo/yr. Our envelope models are flattened towards the equator and the wind terminal velocities in that region are rather high (1000 Km/s). However, in the region near the star the equatorial velocity field is dominated by rotation. RESUMEN. Se presenta un modelo de la estructura de un viento empujado radiativamente en el plano meridional de una estrella caliente. Se incluyeron en las ecuaciones de movimiento los efectos de rotaci6n y la simulaci6n de fuerzas viscosas. Se consider6 la fuerza de las lineas de radiaci6n incluyendo la correcci6n de disco finito en calculos autoconsistentes los cuales incluyen oscurecimiento gravitacional asi como distorsi6n de la estrella por rotaci6n. La aplicaci6n a una estrella tipica BlV lleva a cocientes de flujo de masa entre el ecuador y el polo del orden de 10 de perdida de masa en el intervalo 5.l0 a 10 Mo/ano. Nuestros modelos de envolvente estan achatados hacia el ecuador y las velocidads terminales del viento en esa regi6n son bastante altas (1000 Km/s). Sin embargo, en la regi6n cercana a la estrella el campo de velocidad ecuatorial esta dominado por la rotaci6n. Key words: STARS-BE -- STARS-WINDS

Strong links between metal contamination, habitat modification and estuarine larval fish distributions

International Nuclear Information System (INIS)

McKinley, Andrew C.; Miskiewicz, Anthony; Taylor, Matthew D.; Johnston, Emma L.

2011-01-01

Changes to larval fish assemblages may have far reaching ecological impacts. Correlations between habitat modification, contamination and marine larval fish communities have rarely been assessed in situ. We investigated links between the large-scale distribution of stressors and larval fish assemblages in estuarine environments. Larval fish communities were sampled using a benthic sled within the inner and outer zones of three heavily modified and three relatively unmodified estuaries. Larval abundances were significantly greater in modified estuaries, and there were trends towards greater diversity in these systems. Differences in larval community composition were strongly related to sediment metal levels and reduced seagrass cover. The differences observed were driven by two abundant species, Paedogobius kimurai and Ambassis jacksoniensis, which occurred in large numbers almost exclusively in highly contaminated and pristine locations respectively. These findings suggest that contamination and habitat alteration manifest in substantial differences in the composition of estuarine larval fish assemblages. - Highlights: → We examine contamination/habitat modification impacts on larval fish. → Larvae communities differ between modified/unmodified estuaries. → Larvae are more abundant/diverse in modified areas. → Trends are strongly related to sediment metals/seagrass cover. → Larval impacts have wider ecological importance. - We describe strong links between sediment metals contamination, habitat modification and substantial differences in the composition of the estuarine larval fish assemblage.

Simulation of barotropic wind-driven circulation in tbe Bay of Bengal and Andaman Sea during premonsoon and postmonsoon seasons

Digital Repository Service at National Institute of Oceanography (India)

Unnikrishnan, A.S.; Bahulayan, N.

Two-dimensional vertically integrated model has been used to simulate depth-mean wind-driven circulation during premonsoon and postmonsoon seasons in the upper layers of the Bay of Bengal and Andaman Sea. The model is integrated for 365 d, forcEd...

Estimation of atmospheric turbidity over Ghardaïa city

OpenAIRE

Djafer, Djelloul; Irbah, Abdanour

2013-01-01

International audience; The atmospheric turbidity expresses the attenuation of the solar radiation that reaches the Earth's surface under cloudless sky and describes the optical thickness of the atmosphere. We investigate the atmospheric turbidity over Gharda¨ıa city using two turbidity parameters, the Linke turbidity factor and the Angstr ¨om turbidity coefficient. Their values and temporal variation are obtained from data recorded between 2004 and 2008 at Gharda¨ıa. The results show that bo...

Red Geyser: A New Class of Galaxy with Large-scale AGN-driven Winds

Science.gov (United States)

Roy, Namrata; Bundy, Kevin; Cheung, Edmond; MaNGA Team

2018-01-01

A new class of quiescent (non-star-forming) galaxies harboring possible AGN-driven winds have been discovered using the spatially resolved optical spectroscopy from the ongoing SDSS-IV MaNGA (Sloan Digital Sky Survey-IV Mapping Nearby Galaxies at Apache Point Observatory) survey. These galaxies named "red geysers" constitute 5%-10% of the local quiescent galaxy population and are characterized by narrow bisymmetric ionized gas emission patterns. These enhanced patterns are seen in equivalent width maps of Hα, [OIII] and other strong emission lines. They are co-aligned with the ionized gas velocity gradients but significantly misaligned with stellar velocity gradients. They also show very high gas velocity dispersions (~200 km/s). Considering these observations in light of models of the gravitational potential, Cheung et al. argued that red geysers host large-scale AGN-driven winds of ionized gas that may play a role in suppressing star formation at late times. In this work, we test the hypothesis that AGN activity is ultimately responsible for the red geyser phenomenon. We compare the nuclear radio activity of the red geysers to a matched control sample of galaxies of similar stellar mass, redshift, rest frame NUV–r color and axis ratio. and additionally, control for the presence of ionized gas. We have used 1.4 GHz radio continuum data from the VLA FIRST Survey to stack the radio flux from the red geyser sample and control sample. We find that the red geysers have a higher average radio flux than the control galaxies at > 3σ significance. Our sample is restricted to rest-frame NUV–r color > 5, thus ruling out possible radio emission due to star formation activity. We conclude that red geysers are associated with more active AGN, supporting a feedback picture in which episodic AGN activity drives large-scale but relatively weak ionized winds in many in many early-type galaxies.

Hyperspectral Sensing for Turbid Water Quality Monitoring in Freshwater Rivers: Empirical Relationship between Reflectance and Turbidity and Total Solids

Directory of Open Access Journals (Sweden)

Jiunn-Lin Wu

2014-11-01

Full Text Available Total suspended solid (TSS is an important water quality parameter. This study was conducted to test the feasibility of the band combination of hyperspectral sensing for inland turbid water monitoring in Taiwan. The field spectral reflectance in the Wu river basin of Taiwan was measured with a spectroradiometer; the water samples were collected from the different sites of the Wu river basin and some water quality parameters were analyzed on the sites (in situ as well as brought to the laboratory for further analysis. To obtain the data set for this study, 160 in situ sample observations were carried out during campaigns from August to December, 2005. The water quality results were correlated with the reflectivity to determine the spectral characteristics and their relationship with turbidity and TSS. Furthermore, multiple-regression (MR and artificial neural network (ANN were used to model the transformation function between TSS concentration and turbidity levels of stream water, and the radiance measured by the spectroradiometer. The value of the turbidity and TSS correlation coefficient was 0.766, which implies that turbidity is significantly related to TSS in the Wu river basin. The results indicated that TSS and turbidity are positively correlated in a significant way across the entire spectrum, when TSS concentration and turbidity levels were under 800 mg·L−1 and 600 NTU, respectively. Optimal wavelengths for the measurements of TSS and turbidity are found in the 700 and 900 nm range, respectively. Based on the results, better accuracy was obtained only when the ranges of turbidity and TSS concentration were less than 800 mg·L−1 and less than 600 NTU, respectively and used rather than using whole dataset (R2 = 0.93 versus 0.88 for turbidity and R2 = 0.83 versus 0.58 for TSS. On the other hand, the ANN approach can improve the TSS retrieval using MR. The accuracy of TSS estimation applying ANN (R2 = 0.66 was better than with the MR

Hyperspectral sensing for turbid water quality monitoring in freshwater rivers: Empirical relationship between reflectance and turbidity and total solids.

Science.gov (United States)

Wu, Jiunn-Lin; Ho, Chung-Ru; Huang, Chia-Ching; Srivastav, Arun Lal; Tzeng, Jing-Hua; Lin, Yao-Tung

2014-11-28

Total suspended solid (TSS) is an important water quality parameter. This study was conducted to test the feasibility of the band combination of hyperspectral sensing for inland turbid water monitoring in Taiwan. The field spectral reflectance in the Wu river basin of Taiwan was measured with a spectroradiometer; the water samples were collected from the different sites of the Wu river basin and some water quality parameters were analyzed on the sites (in situ) as well as brought to the laboratory for further analysis. To obtain the data set for this study, 160 in situ sample observations were carried out during campaigns from August to December, 2005. The water quality results were correlated with the reflectivity to determine the spectral characteristics and their relationship with turbidity and TSS. Furthermore, multiple-regression (MR) and artificial neural network (ANN) were used to model the transformation function between TSS concentration and turbidity levels of stream water, and the radiance measured by the spectroradiometer. The value of the turbidity and TSS correlation coefficient was 0.766, which implies that turbidity is significantly related to TSS in the Wu river basin. The results indicated that TSS and turbidity are positively correlated in a significant way across the entire spectrum, when TSS concentration and turbidity levels were under 800 mg·L(-1) and 600 NTU, respectively. Optimal wavelengths for the measurements of TSS and turbidity are found in the 700 and 900 nm range, respectively. Based on the results, better accuracy was obtained only when the ranges of turbidity and TSS concentration were less than 800 mg·L(-1) and less than 600 NTU, respectively and used rather than using whole dataset (R(2) = 0.93 versus 0.88 for turbidity and R(2) = 0.83 versus 0.58 for TSS). On the other hand, the ANN approach can improve the TSS retrieval using MR. The accuracy of TSS estimation applying ANN (R(2) = 0.66) was better than with the MR approach (R

Comparison of driven and simulated "free" stall flutter in a wind tunnel

Science.gov (United States)

Culler, Ethan; Farnsworth, John; Fagley, Casey; Seidel, Jurgen

2016-11-01

Stall flutter and dynamic stall have received a significant amount of attention over the years. To experimentally study this problem, the body undergoing stall flutter is typically driven at a characteristic, single frequency sinusoid with a prescribed pitching amplitude and mean angle of attack offset. This approach allows for testing with repeatable kinematics, however it effectively decouples the structural motion from the aerodynamic forcing. Recent results suggest that this driven approach could misrepresent the forcing observed in a "free" stall flutter scenario. Specifically, a dynamically pitched rigid NACA 0018 wing section was tested in the wind tunnel under two modes of operation: (1) Cyber-Physical where "free" stall flutter was physically simulated through a custom motor-control system modeling a torsional spring and (2) Direct Motor-Driven Dynamic Pitch at a single frequency sinusoid representative of the cyber-physical motion. The time-resolved pitch angle and moment were directly measured and compared for each case. It was found that small deviations in the pitch angle trajectory between these two operational cases generate significantly different aerodynamic pitching moments on the wing section, with the pitching moments nearly 180o out of phase in some cases. This work is supported by the Air Force Office of Scientific Research through the Flow Interactions and Control Program and by the National Defense Science and Engineering Graduate Fellowship Program.

Direct Driven Permanent Magnet Synchronous Generators with Diode Rectifiers for Use in Offshore Wind Turbines

OpenAIRE

Reigstad, Tor Inge

2007-01-01

This work is focused on direct-driven permanent magnets synchronous generators (PMSG) with diode rectifiers for use in offshore wind turbines. Reactive compensation of the generator, power losses and control of the generator are studied. Configurations for power transmission to onshore point of common connection are also considered. Costs, power losses, reliability and interface with the PMSG are discussed. The purpose of the laboratory tests and simulations are to learn how a PMSG with dio...

Non-axisymmetric line-driven disc winds - I. Disc perturbations

Science.gov (United States)

Dyda, Sergei; Proga, Daniel

2018-04-01

We study mass outflows driven from accretion discs by radiation pressure due to spectral lines. To investigate non-axisymmetric effects, we use the ATHENA++ code and develop a new module to account for radiation pressure driving. In 2D, our new simulations are consistent with previous 2D axisymmetric solutions by Proga et al., who used the ZEUS 2D code. Specifically, we find that the disc winds are time dependent, characterized by a dense stream confined to ˜45° relative to the disc mid-plane and bounded on the polar side by a less dense, fast stream. In 3D, we introduce a vertical, ϕ-dependent, subsonic velocity perturbation in the disc mid-plane. The perturbation does not change the overall character of the solution but global outflow properties such as the mass, momentum, and kinetic energy fluxes are altered by up to 100 per cent. Non-axisymmetric density structures develop and persist mainly at the base of the wind. They are relatively small, and their densities can be a few times higher than the azimuthal average. The structure of the non-axisymmetric and axisymmetric solutions differ also in other ways. Perhaps most importantly from the observational point of view are the differences in the so-called clumping factors, that serve as a proxy for emissivity due to two body processes. In particular, the spatially averaged clumping factor over the entire fast stream, while it is of a comparable value in both solutions, it varies about 10 times faster in the non-axisymmetric case.

Differential turbidity measurements at Hanford

International Nuclear Information System (INIS)

Laulainen, N.S.; Bates, J.A.; Kleckner, E.W.; Michalsky, J.J.; Schrotke, P.M.; Thorp, J.M.

1978-01-01

An experiment to exmine differential turbidity effects on measured insolation between the Rattlesnake Observatory and the Hanford Meteorological Station was conducted during summer 1977. Several types of solar radiation instruments were used, including pyranometers, multiwavelength sunphotometers, and an active cavity radiometer. Preliminary results show dramatic temporal variability of aerosol loading at HMS and significant insolation and turbidity differences between the Observatory and HMS

Characteristics and landcover of estuarine boundaries: implications for the delineation of the South African estuarine functional zone

CSIR Research Space (South Africa)

Veldkornet, DA

2015-11-01

Full Text Available Zulu-Natal), cultivation has removed estuarine habitat. Although delineation of boundaries can be complicated by landcover changes, the estuarine lateral boundary in Cape estuaries could be identified based on sediment characteristics (moisture content, organic content...

Influence of estuarine processes on spatiotemporal variation in bioavailable selenium

Science.gov (United States)

Stewart, Robin; Luoma, Samuel N.; Elrick, Kent A.; Carter, James L.; van der Wegen, Mick

2013-01-01

Dynamic processes (physical, chemical and biological) challenge our ability to quantify and manage the ecological risk of chemical contaminants in estuarine environments. Selenium (Se) bioavailability (defined by bioaccumulation), stable isotopes and molar carbon-tonitrogen ratios in the benthic clam Potamocorbula amurensis, an important food source for predators, were determined monthly for 17 yr in northern San Francisco Bay. Se concentrations in the clams ranged from a low of 2 to a high of 22 μg g-1 over space and time. Little of that variability was stochastic, however. Statistical analyses and preliminary hydrodynamic modeling showed that a constant mid-estuarine input of Se, which was dispersed up- and down-estuary by tidal currents, explained the general spatial patterns in accumulated Se among stations. Regression of Se bioavailability against river inflows suggested that processes driven by inflows were the primary driver of seasonal variability. River inflow also appeared to explain interannual variability but within the range of Se enrichment established at each station by source inputs. Evaluation of risks from Se contamination in estuaries requires the consideration of spatial and temporal variability on multiple scales and of the processes that drive that variability.

Wind data for wind driven plant. [site selection for optimal performance

Science.gov (United States)

Stodhart, A. H.

1973-01-01

Simple, averaged wind velocity data provide information on energy availability, facilitate generator site selection and enable appropriate operating ranges to be established for windpowered plants. They also provide a basis for the prediction of extreme wind speeds.

A data-driven multi-model methodology with deep feature selection for short-term wind forecasting

International Nuclear Information System (INIS)

Feng, Cong; Cui, Mingjian; Hodge, Bri-Mathias; Zhang, Jie

2017-01-01

Highlights: • An ensemble model is developed to produce both deterministic and probabilistic wind forecasts. • A deep feature selection framework is developed to optimally determine the inputs to the forecasting methodology. • The developed ensemble methodology has improved the forecasting accuracy by up to 30%. - Abstract: With the growing wind penetration into the power system worldwide, improving wind power forecasting accuracy is becoming increasingly important to ensure continued economic and reliable power system operations. In this paper, a data-driven multi-model wind forecasting methodology is developed with a two-layer ensemble machine learning technique. The first layer is composed of multiple machine learning models that generate individual forecasts. A deep feature selection framework is developed to determine the most suitable inputs to the first layer machine learning models. Then, a blending algorithm is applied in the second layer to create an ensemble of the forecasts produced by first layer models and generate both deterministic and probabilistic forecasts. This two-layer model seeks to utilize the statistically different characteristics of each machine learning algorithm. A number of machine learning algorithms are selected and compared in both layers. This developed multi-model wind forecasting methodology is compared to several benchmarks. The effectiveness of the proposed methodology is evaluated to provide 1-hour-ahead wind speed forecasting at seven locations of the Surface Radiation network. Numerical results show that comparing to the single-algorithm models, the developed multi-model framework with deep feature selection procedure has improved the forecasting accuracy by up to 30%.

Reduction of Turbidity of Water Using Locally Available Natural Coagulants

Science.gov (United States)

Asrafuzzaman, Md.; Fakhruddin, A. N. M.; Hossain, Md. Alamgir

2011-01-01

Turbidity imparts a great problem in water treatment. Moringa oleifera, Cicer arietinum, and Dolichos lablab were used as locally available natural coagulants in this study to reduce turbidity of synthetic water. The tests were carried out, using artificial turbid water with conventional jar test apparatus. Optimum mixing intensity and duration were determined. After dosing water-soluble extracts of Moringa oleifera, Cicer arietinum, and Dolichos lablab reduced turbidity to 5.9, 3.9, and 11.1 nephelometric turbidity unit (NTU), respectively, from 100 NTU and 5, 3.3, and 9.5, NTU, respectively, after dosing and filtration. Natural coagulants worked better with high, turbid, water compare to medium, or low, turbid, water. Highest turbidity reduction efficiency (95.89%) was found with Cicer arietinum. About 89 to 96% total coliform reduction were also found with natural coagulant treatment of turbid water. Using locally available natural coagulants, suitable, easier, and environment friendly options for water treatment were observed. PMID:23724307

Sup(239,240)Pu in estuarine and shelf waters of the north-eastern United States

International Nuclear Information System (INIS)

Sholkovitz, E.R.; Mann, D.R.

1987-01-01

The distribution of sup(239,240)Pu between dissolved and particulate forms has been measured in four estuaries on the north-east coast of the United States (Connecticut River, Delaware Bay, Chesapeake Bay, and Mullica River). The data cover the whole salinity range from freshwater input to shelf waters at 3.5% and includes one profile from a nearly anoxic basin in the Chesapeake Bay. In the organic-rich Mullica River estuary, large-scale removal of riverine dissolved sup(239,240)Pu occurs at low salinities due to salt-induced coagulation, a mechanism analogous to that for iron and humic acids. Within the 0 to 2.5-3.5% zone in the other three estuaries, the activity of dissolved sup(239,240)Pu increases almost conservatively. The activities of particulate sup(239,240)Pu are highest in the more turbid waters of low salinity regime (0-1.5%), but become increasingly insignificant with respect to dissolved sup(239,240)Pu as salinities increase. At higher salinities corresponding to shelf water, there is a sharp increase in dissolved sup(239,240)Pu activity. The dissolved sup(239,240)Pu activity within each estuary appears to be inversely related to the flushing time of water. The sharp decrease in dissolved sup(239,240)Pu activities between shelf and estuarine waters appears to be driven by removal within the estuaries themselves rather than on the shelf. Dissolved sup(239,240)Pu activities are lower in the nearly-anoxic bottom waters of Chesapeake Bay indicating enhanced removal by redox transformation of Pu [i.e., Pu(V) to Pu(IV)]. (author)

Estuarine Ecosystem Engineering : Biogeomorphology in the estuarine intertidal

NARCIS (Netherlands)

Montserrat Trotsenburg, F.

2011-01-01

The aim of this thesis was to investigate how (macro)benthic organisms interact with the ecological functioning, erodibility and small- to medium-scale morphodynamics of estuarine intertidal sediment by modulating its composition and/or properties. In these interactions, scale is of great importance

Coastal circulation and water-column properties in the War in the Pacific National Historical Park, Guam: measurements and modeling of waves, currents, temperature, salinity, and turbidity, April-August 2012

Science.gov (United States)

Storlazzi, Curt D.; Cheriton, Olivia M.; Lescinski, Jamie M.R.; Logan, Joshua B.

2014-01-01

The U.S. Geological Survey (USGS) Pacific Coastal and Marine Science Center (PCMSC) initiated an investigation in the National Park Service’s (NPS) War in the Pacific National Historical Park (WAPA) to provide baseline scientific information on coastal circulation and water-column properties along west-central Guam, focusing on WAPA’s Agat Unit, as it relates to the transport and settlement of coral larvae, fish, and other marine organisms. The oceanographic data and numerical circulation modeling results from this study demonstrate that circulation in Agat Bay was strongly driven by winds and waves at longer (>1 day) timescales and by the tides at shorter (Turbidity was relatively low in Agat Bay and was similar to levels measured elsewhere along west-central Guam. The numerical circulation modeling results provide insight into the potential paths of buoyant material released from a series of locations along west-central Guam under summer non-trade wind forcing conditions that characterize coral spawning events. This information may be useful in evaluating the potential zones of influence/impact resulting from transport by surface currents of material released from these select locations.

High-efficiency wind turbine

Science.gov (United States)

Hein, L. A.; Myers, W. N.

1980-01-01

Vertical axis wind turbine incorporates several unique features to extract more energy from wind increasing efficiency 20% over conventional propeller driven units. System also features devices that utilize solar energy or chimney effluents during periods of no wind.

Polymeric turbidity sensor fabricated by laser direct writing

International Nuclear Information System (INIS)

Li, Shu; Lin, Qiao; Wu, George; Chen, Liuhua; Wu, X

2011-01-01

The design of a miniature-sized turbidity sensor fabricated by laser direct writing was proposed and tested. A dual-beam dual-detector sensing structure was written by a 488 nm laser from UV curable optical polymer to form a 4 mm diameter turbidity sensing probe, with the fabrication process being shortened to a few seconds. Experimental tests on prototypes were conducted by using standard turbidity solutions, and the data were processed with a self-adapting neural network based on a single input single output algorithm. The scattering coefficient for normalized turbidity of the standards was obtained, and system accuracy was validated by an error analysis. Experimental results indicated that in the testing situation presented in this paper, the sensor was capable of responding to turbidity with a relative error of about 3%

Implications of tidally-varying bed stress and intermittent estuarine stratification on fine-sediment dynamics through the Mekong's tidal river to estuarine reach

Science.gov (United States)

McLachlan, R. L.; Ogston, A. S.; Allison, M. A.

2017-09-01

River gauging stations are often located upriver of tidal propagation where sediment transport processes and storage are impacted by widely varying ratios of marine to freshwater influence. These impacts are not yet thoroughly understood. Therefore, sediment fluxes measured at these stations may not be suitable for predicting changes to coastal morphology. To characterize sediment transport dynamics in this understudied zone, flow velocity, salinity, and suspended-sediment properties (concentration, size, and settling velocity) were measured within the tidal Sông Hậu distributary of the lower Mekong River, Vietnam. Fine-sediment aggregation, settling, and trapping rates were promoted by seasonal and tidal fluctuations in near-bed shear stress as well as the intermittent presence of a salt wedge and estuary turbidity maximum. Beginning in the tidal river, fine-grained particles were aggregated in freshwater. Then, in the interface zone between the tidal river and estuary, impeded near-bed shear stress and particle flux convergence promoted settling and trapping. Finally, in the estuary, sediment retention was further encouraged by stratification and estuarine circulation which protected the bed against particle resuspension and enhanced particle aggregation. These patterns promote mud export ( 1.7 t s-1) from the entire study area in the high-discharge season when fluvial processes dominate and mud import ( 0.25 t s-1) into the estuary and interface zone in the low-discharge season when estuarine processes dominate. Within the lower region of the distributaries, morphological change in the form of channel abandonment was found to be promoted within minor distributaries by feedbacks between channel depth, vertical mixing, and aggregate trapping. In effect, this field study sheds light on the sediment trapping capabilities of the tidal river - estuary interface zone, a relatively understudied region upstream of where traditional concepts place sites of deposition

Impact, runoff and drying of wind-driven rain on a window glass surface: numerical modelling based on experimental validation

NARCIS (Netherlands)

Blocken, B.J.E.; Carmeliet, J.E.

2015-01-01

This paper presents a combination of two models to study both the impingement and the contact and surface phenomena of rainwater on a glass window surface: a Computational Fluid Dynamics (CFD) model for the calculation of the distribution of the wind-driven rain (WDR) across the building facade and

Atmospheric turbidity parameters in the high polluted site of egypt

International Nuclear Information System (INIS)

Shaltout, M.A.M.; Rahoma, U.A.

1996-01-01

Monthly variations of Linke, angstrom and Schuepp turbidity coefficients and gamma exponent as well as the influence of climatic factor on them are analysed. For each of these turbidity coefficients; calculated from measurements of broad band filters at Helwan, egypt, desert climate, are reported. A linear regression model fitted to Angstrom's turbidity turbidity coefficient beta and Linke turbidity L for Helwan. The calculation showed that, it is higher values of atmospheric turbidity coefficients due to, both the effect of air pollutants in the Helwan atmosphere from the four cement companies and some of heavy industrial factories, and the effect of the former's desert climate. 6 figs., 2 tabs

Natural Ventilation Driven by Wind and Temperature Difference

DEFF Research Database (Denmark)

Larsen, Tine Steen

Natural ventilation is a commonly used principle when buildings are being ventilated. It can be controlled by openings in the building envelope, which open or close depending on the need of air inside the building. It can also be the simple action of just opening a door or a window to let the fresh...... driving forces are still wind pressure and temperature differences as with cross-ventilation, but here the turbulence in the wind and the pulsating flow near the opening also affect the flow through the opening. From earlier work, some design expressions already exist, but none of these include...... the incidence angle of the wind, which is an important parameter in this type of ventilation. Several wind tunnel experiments are made and from the results of these, a new design expression is made which includes the wind pressure, temperature difference, incidence angle of the wind and the fluctuations...

Utilising monitoring and modelling of estuarine environments to investigate catchment conditions responsible for stratification events in a typically well-mixed urbanised estuary

Science.gov (United States)

Lee, Serena B.; Birch, Gavin F.

2012-10-01

Estuarine health is affected by contamination from stormwater, particularly in highly-urbanised environments. For systems where catchment monitoring is insufficient, novel techniques must be employed to determine the impact of urban runoff on receiving water bodies. In the present work, estuarine monitoring and modelling were successfully employed to determine stormwater runoff volumes and establish an appropriate rainfall/runoff relationship capable of replicating fresh-water discharge due to the full range of precipitation conditions in the Sydney Estuary, Australia. Using estuary response to determine relationships between catchment rainfall and runoff is a widely applicable method and may be of assistance in the study of waterways where monitoring fluvial discharges is not practical or is beyond the capacity of management authorities. For the Sydney Estuary, the SCS-CN method replicated rainfall/runoff and was applied in numerical modelling experiments investigating the hydrodynamic characteristics affecting stratification and estuary recovery following high precipitation. Numerical modelling showed stratification in the Sydney Estuary was dominated by fresh-water discharge. Spring tides and up-estuary winds contributed to mixing and neap tides and down-estuary winds enhanced stratification.

Larval dispersion of the estuarine crab Neohelice granulata in coastal marine waters of the Southwest Atlantic

Science.gov (United States)

Bas, Claudia; Luppi, Tomás; Spivak, Eduardo; Schejter, Laura

2009-08-01

The estuarine brachyuran crab Neohelice granulata export their larvae from the parental intertidal population of the Mar Chiquita coastal lagoon, and probably other populations, to marine waters. The degree of larval dispersion or self-recruitment of populations is unknown. We evaluated the presence of all larval stages of N. granulata in coastal waters of Argentina between 37.9° and 35.8° S, at two different spatial scales: a broad scale of tens to hundreds of kilometers from the Río de la Plata estuary in the north, to Mar Chiquita lagoon in the south, and a small scale of hundreds of meters to some kilometers around the mouth of Mar Chiquita, during spring and summer. Additionally, we registered the larval composition and density at San Clemente creek population, in Samborombon Bay (Río de la Plata estuary), every 3 h along a 30-hour period. Evidence indicates that larval release of N. granulata is temporally synchronized with nocturnal ebb tides and all development from Zoea I to Zoea IV occur in areas close to the parental population, even with very different oceanographic characteristics. A possible mechanism based on salinity selection and wind-driven transport is proposed for such behavior, and some considerations related to the connectivity of present populations are made.

Large eddy simulation of fire-induced buoyancy driven plume dispersion in an urban street canyon under perpendicular wind flow

Energy Technology Data Exchange (ETDEWEB)

Hu, L.H., E-mail: hlh@ustc.edu.cn [State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei, Anhui 230026 (China); Huo, R.; Yang, D. [State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei, Anhui 230026 (China)

2009-07-15

The dispersion of fire-induced buoyancy driven plume in and above an idealized street canyon of 18 m (width) x 18 m (height) x 40 m (length) with a wind flow perpendicular to its axis was investigated by Fire Dynamics Simulator (FDS), Large Eddy Simulation (LES). Former studies, such as that by Oka [T.R. Oke, Street design and urban canopy layer climate, Energy Build. 11 (1988) 103-113], Gayev and Savory [Y.A. Gayev, E. Savory, Influence of street obstructions on flow processes within street canyons. J. Wind Eng. Ind. Aerodyn. 82 (1999) 89-103], Xie et al. [S. Xie, Y. Zhang, L. Qi, X. Tang, Spatial distribution of traffic-related pollutant concentrations in street canyons. Atmos. Environ. 37 (2003) 3213-3224], Baker et al. [J. Baker, H. L. Walker, X. M. Cai, A study of the dispersion and transport of reactive pollutants in and above street canyons-a large eddy simulation, Atmos. Environ. 38 (2004) 6883-6892] and Baik et al. [J.-J. Baik, Y.-S. Kang, J.-J. Kim, Modeling reactive pollutant dispersion in an urban street canyon, Atmos. Environ. 41 (2007) 934-949], focus on the flow pattern and pollutant dispersion in the street canyon with no buoyancy effect. Results showed that with the increase of the wind flow velocity, the dispersion pattern of a buoyant plume fell into four regimes. When the wind flow velocity increased up to a certain critical level, the buoyancy driven upward rising plume was re-entrained back into the street canyon. This is a dangerous situation as the harmful fire smoke will accumulate to pollute the environment and thus threaten the safety of the people in the street canyon. This critical re-entrainment wind velocity, as an important parameter to be concerned, was further revealed to increase asymptotically with the heat/buoyancy release rate of the fire.

Large eddy simulation of fire-induced buoyancy driven plume dispersion in an urban street canyon under perpendicular wind flow.

Science.gov (United States)

Hu, L H; Huo, R; Yang, D

2009-07-15

The dispersion of fire-induced buoyancy driven plume in and above an idealized street canyon of 18 m (width) x 18 m (height) x 40 m (length) with a wind flow perpendicular to its axis was investigated by Fire Dynamics Simulator (FDS), Large Eddy Simulation (LES). Former studies, such as that by Oka [T.R. Oke, Street design and urban canopy layer climate, Energy Build. 11 (1988) 103-113], Gayev and Savory [Y.A. Gayev, E. Savory, Influence of street obstructions on flow processes within street canyons. J. Wind Eng. Ind. Aerodyn. 82 (1999) 89-103], Xie et al. [S. Xie, Y. Zhang, L. Qi, X. Tang, Spatial distribution of traffic-related pollutant concentrations in street canyons. Atmos. Environ. 37 (2003) 3213-3224], Baker et al. [J. Baker, H. L. Walker, X. M. Cai, A study of the dispersion and transport of reactive pollutants in and above street canyons--a large eddy simulation, Atmos. Environ. 38 (2004) 6883-6892] and Baik et al. [J.-J. Baik, Y.-S. Kang, J.-J. Kim, Modeling reactive pollutant dispersion in an urban street canyon, Atmos. Environ. 41 (2007) 934-949], focus on the flow pattern and pollutant dispersion in the street canyon with no buoyancy effect. Results showed that with the increase of the wind flow velocity, the dispersion pattern of a buoyant plume fell into four regimes. When the wind flow velocity increased up to a certain critical level, the buoyancy driven upward rising plume was re-entrained back into the street canyon. This is a dangerous situation as the harmful fire smoke will accumulate to pollute the environment and thus threaten the safety of the people in the street canyon. This critical re-entrainment wind velocity, as an important parameter to be concerned, was further revealed to increase asymptotically with the heat/buoyancy release rate of the fire.

Large eddy simulation of fire-induced buoyancy driven plume dispersion in an urban street canyon under perpendicular wind flow

International Nuclear Information System (INIS)

Hu, L.H.; Huo, R.; Yang, D.

2009-01-01

The dispersion of fire-induced buoyancy driven plume in and above an idealized street canyon of 18 m (width) x 18 m (height) x 40 m (length) with a wind flow perpendicular to its axis was investigated by Fire Dynamics Simulator (FDS), Large Eddy Simulation (LES). Former studies, such as that by Oka [T.R. Oke, Street design and urban canopy layer climate, Energy Build. 11 (1988) 103-113], Gayev and Savory [Y.A. Gayev, E. Savory, Influence of street obstructions on flow processes within street canyons. J. Wind Eng. Ind. Aerodyn. 82 (1999) 89-103], Xie et al. [S. Xie, Y. Zhang, L. Qi, X. Tang, Spatial distribution of traffic-related pollutant concentrations in street canyons. Atmos. Environ. 37 (2003) 3213-3224], Baker et al. [J. Baker, H. L. Walker, X. M. Cai, A study of the dispersion and transport of reactive pollutants in and above street canyons-a large eddy simulation, Atmos. Environ. 38 (2004) 6883-6892] and Baik et al. [J.-J. Baik, Y.-S. Kang, J.-J. Kim, Modeling reactive pollutant dispersion in an urban street canyon, Atmos. Environ. 41 (2007) 934-949], focus on the flow pattern and pollutant dispersion in the street canyon with no buoyancy effect. Results showed that with the increase of the wind flow velocity, the dispersion pattern of a buoyant plume fell into four regimes. When the wind flow velocity increased up to a certain critical level, the buoyancy driven upward rising plume was re-entrained back into the street canyon. This is a dangerous situation as the harmful fire smoke will accumulate to pollute the environment and thus threaten the safety of the people in the street canyon. This critical re-entrainment wind velocity, as an important parameter to be concerned, was further revealed to increase asymptotically with the heat/buoyancy release rate of the fire.

Algal stabilisation of estuarine sediments

International Nuclear Information System (INIS)

1992-01-01

The presence of benthic microalgae can increase the stability of intertidal sediments and influence sediment fluxes within an estuarine environment. Therefore the relative importance of algal stabilisation needs to be understood to help predict the effects of a tidal barrage. The biogenic stabilisation of intertidal estuarine sediments by epipelic diatom films and the macrophyte Vaucheria was studied at three sites on the Severn Estuary. The cohesive strength meter (CSM) was developed to measure surface critical shear stress with varied algal density. A number of techniques have been used to determine the general in situ erodibility of cohesive estuarine sediments. The measurements of sediment shear strength and critical erosion velocity were investigated. Field experiments were undertaken to investigate the effect of algae on binding sediments, and a predictive method for the assessment of sediment stabilisation by algal binding was developed. (author)

Fauna and habitat types driven by turbidity currents in the lobe complex of the Congo deep-sea fan

Science.gov (United States)

Sen, Arunima; Dennielou, Bernard; Tourolle, Julie; Arnaubec, Aurélien; Rabouille, Christophe; Olu, Karine

2017-08-01

This study characterizes the habitats and megafaunal community of the Congo distal lobe complex driven by turbidity currents through the use of remotely operated vehicle (ROV) still imagery transects covering distances in the order of kilometers. In this sedimentary, abyssal area about 5000 m deep and 750 km offshore from western Africa, large quantities of deposited organic material supplied by the Congo River canyon and channel support aggregations of large sized foraminifers (Bathysiphon sp.) and vesicomyid clams (Christineconcha regab, Abyssogena southwardae) often associated with methane cold seeps, as well as opportunistic deep-sea scavengers. Additionally, bacterial mats, assumed to be formed by large sulfur-oxidizing filamentous bacteria (Beggiatoa type), and black patches of presumably reduced sediment were seen which are, together with sulfur-oxidizing symbiont- bearing vesicomyids, indicators of sulfide-rich sediments. Habitat and faunal distribution were analyzed in relation to the microtopography obtained with the ROV multibeam echosounder, at three sites from the entrance of the lobe complex where the channel is still deep, to the main, flatter area of turbidite deposition. Specific characteristics of the system influence animal distributions: both the forams and the vesicomyid clams tended to avoid the channels characterized by high-speed currents, and are therefore preferentially located along channel flanks affected by sliding, and on levees formed by channel overspill. Foram fields are found in flat areas and form large fields, whereas the vesicomyids have a patchy distribution and appear to show a preference for regions of local topographical relief such as slide scars or collapsed blocks of sediments, which likely facilitate sulfide exhumation. The colonization of sulfide rich sediments by vesicomyids is limited, but nonetheless was seen to occur in the main deposition area where they have to cope with very high sedimentation rates (up to 20 cm

Turbidity in oil-in-water-emulsions - Key factors and visual perception.

Science.gov (United States)

Linke, C; Drusch, S

2016-11-01

The aim of the present study is to systematically describe the factors affecting turbidity in beverage emulsions and to get a better understanding of visual perception of turbidity. The sensory evaluation of the human visual perception of turbidity showed that humans are most sensitive to turbidity differences between two samples in the range between 1000 and 1500 NTU (ratio) (nephelometric turbidity units). At very high turbidity values >2000 TU in NTU (ratio) were needed to distinguish between samples that they were perceived significantly different. Particle size was the most important factor affecting turbidity. It was shown that a maximum turbidity occurs at a mean volume - surface diameter of 0.2μm for the oil droplet size. Additional parameters were the refractive index, the composition of the aqueous phase and the presence of excess emulsifier. In a concentration typical for a beverage emulsion a change in the refractive index of the oil phase may allow the alteration of turbidity by up to 30%. With the knowledge on visual perception of turbidity and the determining factors, turbidity can be tailored in product development according to the customer requirements and in quality control to define acceptable variations in optical appearance. Copyright © 2016. Published by Elsevier Ltd.

Wind Regimes in Complex Terrain of the Great Valley of Eastern Tennessee

Energy Technology Data Exchange (ETDEWEB)

Birdwell, Kevin R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2011-05-01

This research was designed to provide an understanding of physical wind mechanisms within the complex terrain of the Great Valley of Eastern Tennessee to assess the impacts of regional air flow with regard to synoptic and mesoscale weather changes, wind direction shifts, and air quality. Meteorological data from 2008 2009 were analyzed from 13 meteorological sites along with associated upper level data. Up to 15 ancillary sites were used for reference. Two-step complete linkage and K-means cluster analyses, synoptic weather studies, and ambient meteorological comparisons were performed to generate hourly wind classifications. These wind regimes revealed seasonal variations of underlying physical wind mechanisms (forced channeled, vertically coupled, pressure-driven, and thermally-driven winds). Synoptic and ambient meteorological analysis (mixing depth, pressure gradient, pressure gradient ratio, atmospheric and surface stability) suggested up to 93% accuracy for the clustered results. Probabilistic prediction schemes of wind flow and wind class change were developed through characterization of flow change data and wind class succession. Data analysis revealed that wind flow in the Great Valley was dominated by forced channeled winds (45 67%) and vertically coupled flow (22 38%). Down-valley pressure-driven and thermally-driven winds also played significant roles (0 17% and 2 20%, respectively), usually accompanied by convergent wind patterns (15 20%) and large wind direction shifts, especially in the Central/Upper Great Valley. The behavior of most wind regimes was associated with detectable pressure differences between the Lower and Upper Great Valley. Mixing depth and synoptic pressure gradients were significant contributors to wind pattern behavior. Up to 15 wind classes and 10 sub-classes were identified in the Central Great Valley with 67 joined classes for the Great Valley at-large. Two-thirds of Great Valley at-large flow was defined by 12 classes. Winds

40 CFR 141.22 - Turbidity sampling and analytical requirements.

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 22 2010-07-01 2010-07-01 false Turbidity sampling and analytical... § 141.22 Turbidity sampling and analytical requirements. The requirements in this section apply to... the water distribution system at least once per day, for the purposes of making turbidity measurements...

Further development in theory/data closure of the photoelectron-driven polar wind and day-night transition of the outflow

Directory of Open Access Journals (Sweden)

S. W. Y. Tam

Full Text Available Recent in situ observations have revealed novel features in the polar wind. Measurements between 5000 and 9000 km altitude by the Akebono satellite indicate that both H⁺ and O⁺ ions can have remarkably higher outflow velocities in the sunlit region than on the nightside. Electrons also display an asymmetric behavior: the dayside difference in energy spread, greater for upward-moving than downward-moving electrons, is absent on the nightside. Here, we discuss the further development of a theory by Tam et al. that can explain most of these observed peculiar properties by properly taking into account the global, kinetic, collisional effects of the sunlit photoelectrons, on the background polar wind and the electric field. Quantitative comparisons of the calculated results with actual data will be described. In addition, transition from the daytime photoelectron-driven polar wind to the night-time polar wind will be discussed.

Turbidity and microbes removal from water using an electrochemical filter

International Nuclear Information System (INIS)

Venkateswaran, G.; Gokhale, B.K.; Belapurkar, A.D.; Kumbhar, A.G.; Balaji, V.

2004-01-01

An in-house designed and fabricated Electrochemical fibrous graphite filter (ECF) was used to remove turbidity and microbes. The filter was found to be effective in removing sub micron size indium turbidity from RAPS-1 moderator water, iron turbidity from Active Process Cooling Water (APCW) of Kaiga Generating Station and microbial reduction from process cooling water RAPS-2. Unlike conventional turbidity removal by addition of coagulants and biocide chemical additions for purification, ECF is a clean way to remove the turbidity without contaminating the system and is best suited for close loop systems

Observed vulnerability of Filchner-Ronne Ice Shelf to wind-driven inflow of warm deep water

Science.gov (United States)

Darelius, E.; Fer, I.; Nicholls, K. W.

2016-01-01

The average rate of melting at the base of the large Filchner-Ronne Ice Shelf in the southern Weddell Sea is currently low, but projected to increase dramatically within the next century. In a model study, melt rates increase as changing ice conditions cause a redirection of a coastal current, bringing warm water of open ocean origin through the Filchner Depression and into the Filchner Ice Shelf cavity. Here we present observations from near Filchner Ice Shelf and from the Filchner Depression, which show that pulses of warm water already arrive as far south as the ice front. This southward heat transport follows the eastern flank of the Filchner Depression and is found to be directly linked to the strength of a wind-driven coastal current. Our observations emphasize the potential sensitivity of Filchner-Ronne Ice Shelf melt rates to changes in wind forcing. PMID:27481659

A comparison of the performance of three types of passive fog gauges under conditions of wind-driven fog and precipitation

NARCIS (Netherlands)

Frumau, K.F.A.; Burkard, R.; Schmid, S.; Bruijnzeel, L.A.; Tobón, C.; Calvo-Alvado\\, J.C.

2011-01-01

Understanding of the 'typical' amounts of fog intercepted by different types of cloud forests is hampered by a lack of comparative information on local fog climatology. Usually some kind of 'fog gauge' is used to characterize fog occurrence and amounts. Moreover, wind-driven fog and precipitation

Resuspension and estuarine nutrient cycling: insights from the Neuse River Estuary

Directory of Open Access Journals (Sweden)

D. R. Corbett

2010-10-01

Full Text Available For at least the past several decades, North Carolina's Neuse River Estuary (NRE has been subject to water quality problems relating to increased eutrophication. Research initiated in the past several years have addressed the nutrient processes of the water column and the passive diffusion processes of the benthic sedimentary environment. Resuspension of bottom sediments, by bioturbation, tides, or winds, may also have a significant effect on the flux of nutrients in an estuarine system These processes can result in the advective transport of sediment porewater, rich with nitrogen, phosphorus and carbon, into the water column. Thus, estimates of nutrient and carbon inputs from the sediments may be too low.

This study focused on the potential change in bottom water nutrient concentrations associated with measured resuspension events. Previous research used short-lived radionuclides and meteorological data to characterize the sediment dynamics of the benthic system of the estuary. These techniques in conjunction with the presented porewater inventories allowed evaluation of the depth to which sediments have been disturbed and the advective flux of nutrients to the water column. The largest removal episode occurred in the lower NRE as the result of a wind event and was estimated that the top 2.2 cm of sediment and corresponding porewater were removed. NH₄⁺ advective flux (resuspended was 2 to 6 times greater than simply diffusion. Phosphate fluxes were estimated to be 15 times greater than the benthic diffusive flux. Bottom water conditions with elevated NH₄⁺ and PO₄³⁻ indicate that nutrients stored in the sediments continue to play an important role in overall water quality and this study suggests that the advective flux of nutrients to the water column is critical to understand estuarine nutrient cycling.

Assessing the risk posed by high-turbidity water to water supplies.

Science.gov (United States)

Chang, Chia-Ling; Liao, Chung-Sheng

2012-05-01

The objective of this study is to assess the risk of insufficient water supply posed by high-turbidity water. Several phenomena can pose risks to the sufficiency of a water supply; this study concerns risks to water treatment plants from particular properties of rainfall and raw water turbidity. High-turbidity water can impede water treatment plant operations; rainfall properties can influence the degree of soil erosion. Thus, water turbidity relates to rainfall characteristics. Exceedance probabilities are presented for different rainfall intensities and turbidities of water. When the turbidity of raw water is higher than 5,000 NTU, it can cause operational problems for a water treatment plant. Calculations show that the turbidity of raw water at the Ban-Sin water treatment plant will be higher than 5,000 NTU if the rainfall intensity is larger than 165 mm/day. The exceedance probability of high turbidity (turbidity >5,000 NTU) in the Ban-Sin water treatment plant is larger than 10%. When any water treatment plant cannot work regularly, its ability to supply water to its customers is at risk.

Proactive monitoring of a wind turbine array with lidar measurements, SCADA data and a data-driven RANS solver

Science.gov (United States)

Iungo, G.; Said, E. A.; Santhanagopalan, V.; Zhan, L.

2016-12-01

Power production of a wind farm and durability of wind turbines are strongly dependent on non-linear wake interactions occurring within a turbine array. Wake dynamics are highly affected by the specific site conditions, such as topography and local atmospheric conditions. Furthermore, contingencies through the life of a wind farm, such as turbine ageing and off-design operations, make prediction of wake interactions and power performance a great challenge in wind energy. In this work, operations of an onshore wind turbine array were monitored through lidar measurements, SCADA and met-tower data. The atmospheric wind field investing the wind farm was estimated by using synergistically the available data through five different methods, which are characterized by different confidence levels. By combining SCADA data and the lidar measurements, it was possible to estimate power losses connected with wake interactions. For this specific array, power losses were estimated to be 4% and 2% of the total power production for stable and convective atmospheric regimes, respectively. The entire dataset was then leveraged for the calibration of a data-driven RANS (DDRANS) solver for prediction of wind turbine wakes and power production. The DDRANS is based on a parabolic formulation of the Navier-Stokes equations with axisymmetry and boundary layer approximations, which allow achieving very low computational costs. Accuracy in prediction of wind turbine wakes and power production is achieved through an optimal tuning of the turbulence closure model. The latter is based on a mixing length model, which was developed based on previous wind turbine wake studies carried out through large eddy simulations and wind tunnel experiments. Several operative conditions of the wind farm under examination were reproduced through DDRANS for different stability regimes, wind directions and wind velocity. The results show that DDRANS is capable of achieving a good level of accuracy in prediction

Compact turbidity meter

Science.gov (United States)

Hirschberg, J. G.

1979-01-01

Proposed monitor that detects back-reflected infrared radiation makes in situ turbidity measurements of lakes, streams, and other bodies of water. Monitor is compact, works well in daylight as at night, and is easily operated in rough seas.

Climate-change refugia: shading reef corals by turbidity.

Science.gov (United States)

Cacciapaglia, Chris; van Woesik, Robert

2016-03-01

Coral reefs have recently experienced an unprecedented decline as the world's oceans continue to warm. Yet global climate models reveal a heterogeneously warming ocean, which has initiated a search for refuges, where corals may survive in the near future. We hypothesized that some turbid nearshore environments may act as climate-change refuges, shading corals from the harmful interaction between high sea-surface temperatures and high irradiance. We took a hierarchical Bayesian approach to determine the expected distribution of 12 coral species in the Indian and Pacific Oceans, between the latitudes 37°N and 37°S, under representative concentration pathway 8.5 (W m(-2) ) by 2100. The turbid nearshore refuges identified in this study were located between latitudes 20-30°N and 15-25°S, where there was a strong coupling between turbidity and tidal fluctuations. Our model predicts that turbidity will mitigate high temperature bleaching for 9% of shallow reef habitat (to 30 m depth) - habitat that was previously considered inhospitable under ocean warming. Our model also predicted that turbidity will protect some coral species more than others from climate-change-associated thermal stress. We also identified locations where consistently high turbidity will likely reduce irradiance to turbid nearshore refuges identified in this study, particularly in the northwestern Hawaiian Islands, the northern Philippines, the Ryukyu Islands (Japan), eastern Vietnam, western and eastern Australia, New Caledonia, the northern Red Sea, and the Arabian Gulf, should become part of a judicious global strategy for reef-coral persistence under climate change. © 2015 John Wiley & Sons Ltd.

Origin and composition of particulate organic matter in a macrotidal turbid estuary: The Gironde Estuary, France

Science.gov (United States)

Savoye, Nicolas; David, Valérie; Morisseau, François; Etcheber, Henri; Abril, Gwenaël; Billy, Isabelle; Charlier, Karine; Oggian, Georges; Derriennic, Hervé; Sautour, Benoît

2012-08-01

At the interface between continent and ocean, estuaries receive particles, and especially particulate organic matter (POM) originating from these two reservoirs, but also produce POM, through autochthonous primary production. The origin and composition of surface POM in the Gironde Estuary (SW France) and the environmental forcing of its variability was investigated using the data set produced by the French Coastal Monitoring Network SOMLIT (Service d'Observation en Milieu LITtoral; monthly like sampling during years 2007-2009). This estuary is considered as a model of macrotidal turbid estuaries. Using elemental and isotopic composition of the POM, we estimated that, at the inner estuary space scale and inter-annual time scale, surface particulate organic carbon (POC) was composed of terrestrial POM originated from the turbidity maximum (96.4%; refractory POC) and flood events (1.6%; labile and refractory POC), and of riverine (0.1%), estuarine (0.8%) and marine (1.1%) phytoplankton, i.e. that POC was 98% and 2% of terrestrial and phytoplankton origin, respectively. However, there was a clear spatial gradient: the phytoplankton contribution increases from ca. 1% in the upper and middle estuary to 8.5% in the lower estuary, where light condition is more favourable to plankton growth. The low contribution of phytoplankton to the POC is a characteristic of the Gironde estuary and contrast with other large temperate estuaries. Statistical analysis indicates that salinity, river flow and SPM concentration, and thus associated hydro-dynamic and sedimentary processes, were the only environmental forcings to the composition of surface POC in this system, at intra- and inter-annual time scale. In contrast, temperature and nutrient concentrations, and thus associated processes, do not force this composition of POC. By combining POC fluxes entering the inner estuary (literature data), POC loss as dissolved organic carbon and CO2 and as sediment trapping within the inner

MAGNETICALLY DRIVEN ACCRETION DISK WINDS AND ULTRA-FAST OUTFLOWS IN PG 1211+143

International Nuclear Information System (INIS)

Fukumura, Keigo; Tombesi, Francesco; Kazanas, Demosthenes; Shrader, Chris; Behar, Ehud; Contopoulos, Ioannis

2015-01-01

We present a study of X-ray ionization of MHD accretion-disk winds in an effort to constrain the physics underlying the highly ionized ultra-fast outflows (UFOs) inferred by X-ray absorbers often detected in various sub classes of Seyfert active galactic nuclei (AGNs). Our primary focus is to show that magnetically driven outflows are indeed physically plausible candidates for the observed outflows accounting for the AGN absorption properties of the present X-ray spectroscopic observations. Employing a stratified MHD wind launched across the entire AGN accretion disk, we calculate its X-ray ionization and the ensuing X-ray absorption-line spectra. Assuming an appropriate ionizing AGN spectrum, we apply our MHD winds to model the absorption features in an XMM-Newton/EPIC spectrum of the narrow-line Seyfert, PG 1211+143. We find, through identifying the detected features with Fe Kα transitions, that the absorber has a characteristic ionization parameter of log (ξ c [erg cm s −1 ]) ≃ 5–6 and a column density on the order of N H ≃ 10 23 cm −2 outflowing at a characteristic velocity of v c /c ≃ 0.1–0.2 (where c is the speed of light). The best-fit model favors its radial location at r c ≃ 200 R o (R o is the black hole’s innermost stable circular orbit), with an inner wind truncation radius at R t ≃ 30 R o . The overall K-shell feature in the data is suggested to be dominated by Fe xxv with very little contribution from Fe xxvi and weakly ionized iron, which is in good agreement with a series of earlier analyses of the UFOs in various AGNs, including PG 1211+143

Rotor Speed Control of a Direct-Driven Permanent Magnet Synchronous Generator-Based Wind Turbine Using Phase-Lag Compensators to Optimize Wind Power Extraction

Directory of Open Access Journals (Sweden)

Ester Hamatwi

2017-01-01

Full Text Available Due to the intermittent nature of wind, the wind power output tends to be inconsistent, and hence maximum power point tracking (MPPT is usually employed to optimize the power extracted from the wind resource at a wide range of wind speeds. This paper deals with the rotor speed control of a 2 MW direct-driven permanent magnet synchronous generator (PMSG to achieve MPPT. The proportional-integral (PI, proportional-derivative (PD, and proportional-integral-derivative (PID controllers have widely been employed in MPPT studies owing to their simple structure and simple design procedure. However, there are a number of shortcomings associated with these controllers; the trial-and-error design procedure used to determine the P, I, and D gains presents a possibility for poorly tuned controller gains, which reduces the accuracy and the dynamic performance of the entire control system. Moreover, these controllers’ linear nature, constricted operating range, and their sensitivity to changes in machine parameters make them ineffective when applied to nonlinear and uncertain systems. On the other hand, phase-lag compensators are associated with a design procedure that is well defined from fundamental principles as opposed to the aforementioned trial-and-error design procedure. This makes the latter controller type more accurate, although it is not well developed yet, and hence it is the focus of this paper. The simulation results demonstrated the effectiveness of the proposed MPPT controller.

design of a small scale wind generator for low wind speed areas

African Journals Online (AJOL)

USER

Most small scale level wind turbine generators are directly driven system, variable speed, and partially ... the best solutions for small-scale wind power plants. Low-speed multi-pole PM generators ..... Designs of the Same Magnet Structure for.

Fish assemblage structure of Koycegiz Lagoon Estuary, Turkey: Spatial and temporal distribution patterns in relation to environmental variation

Science.gov (United States)

Akin, S.; Buhan, E.; Winemiller, K. O.; Yilmaz, H.

2005-09-01

Spatial and temporal variation in fish assemblage structure of Koycegiz Lagoon-Estuarine System (KLES), located on the northwestern Turkish coast of Mediterranean, was investigated along an estuarine gradient where salinity ranged from 5 in upper reaches to 40 in lower reaches during October 1993-September 1994. Throughout the study, 42 species, consisting of marine (25), marine-estuarine-dependent (12), freshwater (3), catadromous (1), and estuarine resident (1) forms, were collected in trammel nets. Although species richness of marine species was greater than that of other groups, numerical contribution by marine species to the total catch was only 16%. Tilapia spp., the most abundant species mostly during summer and early spring at upper reaches, contributed 17% of the total samples. Among the seven species of Mugilidae, which contributed 42% of the total catch, Mugil cephalus, Liza aurata, and Liza salines contributed 10, 13, and 10% of the total catch, respectively. Consistent with findings from other studies, species richness and abundance were highest during late spring and summer and the lowest during winter and early spring. Samples from sites at or near the sea had more marine species. Samples from upper reaches had more freshwater and marine-estuarine-dependent species. Canonical correspondence analysis (CCA) indicated that salinity and turbidity were the most important environmental parameters affecting fishes. Sites near the sea were associated with high salinity and low turbidity, and sites in upper reaches had low salinity and high turbidity. Thus, the pattern observed in fish assemblage structure appears to be strongly influenced by species' responses to dominant salinity and turbidity gradients.

Microscopic imaging through turbid media Monte Carlo modeling and applications

CERN Document Server

Gu, Min; Deng, Xiaoyuan

2015-01-01

This book provides a systematic introduction to the principles of microscopic imaging through tissue-like turbid media in terms of Monte-Carlo simulation. It describes various gating mechanisms based on the physical differences between the unscattered and scattered photons and method for microscopic image reconstruction, using the concept of the effective point spread function. Imaging an object embedded in a turbid medium is a challenging problem in physics as well as in biophotonics. A turbid medium surrounding an object under inspection causes multiple scattering, which degrades the contrast, resolution and signal-to-noise ratio. Biological tissues are typically turbid media. Microscopic imaging through a tissue-like turbid medium can provide higher resolution than transillumination imaging in which no objective is used. This book serves as a valuable reference for engineers and scientists working on microscopy of tissue turbid media.

Wind Power Utilization Guide.

Science.gov (United States)

1981-09-01

The expres- sions for the rotor torque for a Darrieus machine can be found in Reference 4.16. The Darrieus wind turbine offers the following... turbine generators, wind -driven turbines , power conditioning, wind power, energy conservation, windmills, economic ana \\sis. 20 ABS 1"ACT (Conti,on... turbines , power conditioning requirements, siting requirements, and the economics of wind power under different conditions. Three examples are given to

Forecasting wind-driven wildfires using an inverse modelling approach

Directory of Open Access Journals (Sweden)

O. Rios

2014-06-01

Full Text Available A technology able to rapidly forecast wildfire dynamics would lead to a paradigm shift in the response to emergencies, providing the Fire Service with essential information about the ongoing fire. This paper presents and explores a novel methodology to forecast wildfire dynamics in wind-driven conditions, using real-time data assimilation and inverse modelling. The forecasting algorithm combines Rothermel's rate of spread theory with a perimeter expansion model based on Huygens principle and solves the optimisation problem with a tangent linear approach and forward automatic differentiation. Its potential is investigated using synthetic data and evaluated in different wildfire scenarios. The results show the capacity of the method to quickly predict the location of the fire front with a positive lead time (ahead of the event in the order of 10 min for a spatial scale of 100 m. The greatest strengths of our method are lightness, speed and flexibility. We specifically tailor the forecast to be efficient and computationally cheap so it can be used in mobile systems for field deployment and operativeness. Thus, we put emphasis on producing a positive lead time and the means to maximise it.

Performance Evaluation of Five Turbidity Sensors in Three Primary Standards

Science.gov (United States)

Snazelle, Teri T.

2015-10-28

Open-File Report 2015-1172 is temporarily unavailable.Five commercially available turbidity sensors were evaluated by the U.S. Geological Survey, Hydrologic Instrumentation Facility (HIF) for accuracy and precision in three types of turbidity standards; formazin, StablCal, and AMCO Clear (AMCO–AEPA). The U.S. Environmental Protection Agency (EPA) recognizes all three turbidity standards as primary standards, meaning they are acceptable for reporting purposes. The Forrest Technology Systems (FTS) DTS-12, the Hach SOLITAX sc, the Xylem EXO turbidity sensor, the Yellow Springs Instrument (YSI) 6136 turbidity sensor, and the Hydrolab Series 5 self-cleaning turbidity sensor were evaluated to determine if turbidity measurements in the three primary standards are comparable to each other, and to ascertain if the primary standards are truly interchangeable. A formazin 4000 nephelometric turbidity unit (NTU) stock was purchased and dilutions of 40, 100, 400, 800, and 1000 NTU were made fresh the day of testing. StablCal and AMCO Clear (for Hach 2100N) standards with corresponding concentrations were also purchased for the evaluation. Sensor performance was not evaluated in turbidity levels less than 40 NTU due to the unavailability of polymer-bead turbidity standards rated for general use. The percent error was calculated as the true (not absolute) difference between the measured turbidity and the standard value, divided by the standard value.The sensors that demonstrated the best overall performance in the evaluation were the Hach SOLITAX and the Hydrolab Series 5 turbidity sensor when the operating range (0.001–4000 NTU for the SOLITAX and 0.1–3000 NTU for the Hydrolab) was considered in addition to sensor accuracy and precision. The average percent error in the three standards was 3.80 percent for the SOLITAX and -4.46 percent for the Hydrolab. The DTS-12 also demonstrated good accuracy with an average percent error of 2.02 percent and a maximum relative standard

Foraminifera, Thecamoebians and Palynomorphs as Hydrodynamic Indicators in Araguari Estuary, Amazonian Coast, Amapá State – Brazil

Directory of Open Access Journals (Sweden)

Odete Fátima Machado

2010-01-01

Full Text Available The Araguari estuarine dynamics is singular among traditional models of estuaries under tidal regime due to influence of macrotidal and tidal bore. In order to establish estuarine zones in Araguari according foraminifera, thecamoebians, paliynomorphs and physical-chemistry parameters, sixteen sample stations were established along the estuary. Turbidity and temperature were the environmental parameters which allowed determination of the estuarine gradient. Eighteen species of foraminifera, ten of thecamoebians and fourteen of particulate organic matter types were identified. Cluster analysis in R-mode showed three microorganism assemblages and four palynomorph ones. The CCA analyze shows turbidity and total organic matter with the most influence over foraminiferal and thecamoebians distribution at Araguari. Clustering analysis in Q-mode using all data formed four groups suggesting three estuarine zones in Araguari: Zone I composed of thecamoebian species and continental palynomorphs; Zone II - composed by mangrove foraminifera, thecamoebians and all palynomorph assemblages; and Zone III – composed by mangrove and estuarine foraminifera and all palynomorph assemblages.

Momentum-driven Winds from Radiatively Efficient Black Hole Accretion and Their Impact on Galaxies

Science.gov (United States)

Brennan, Ryan; Choi, Ena; Somerville, Rachel S.; Hirschmann, Michaela; Naab, Thorsten; Ostriker, Jeremiah P.

2018-06-01

We explore the effect of momentum-driven winds representing radiation-pressure-driven outflows from accretion onto supermassive black holes in a set of numerical hydrodynamical simulations. We explore two matched sets of cosmological zoom-in runs of 24 halos with masses ∼1012.0–1013.4 M ⊙ run with two different feedback models. Our “NoAGN” model includes stellar feedback via UV heating, stellar winds and supernovae, photoelectric heating, and cosmic X-ray background heating from a metagalactic background. Our fiducial “MrAGN” model is identical except that it also includes a model for black hole seeding and accretion, as well as heating and momentum injection associated with the radiation from black hole accretion. Our MrAGN model launches galactic outflows, which result in both “ejective” feedback—the outflows themselves that drive gas out of galaxies—and “preventative” feedback, which suppresses the inflow of new and recycling gas. As much as 80% of outflowing galactic gas can be expelled, and accretion can be suppressed by as much as a factor of 30 in the MrAGN runs when compared with the NoAGN runs. The histories of NoAGN galaxies are recycling dominated, with ∼70% of material that leaves the galaxy eventually returning, and the majority of outflowing gas reaccretes on 1 Gyr timescales without AGN feedback. Outflowing gas in the MrAGN runs has a higher characteristic velocity (500–1000 km s‑1 versus 100–300 km s‑1 for outflowing NoAGN gas) and travels as far as a few megaparsecs. Only ∼10% of ejected material is reaccreted in the MrAGN galaxies.

Theories for the winds from Wolf Rayet stars

International Nuclear Information System (INIS)

Cassinelli, J.P.

1982-01-01

The massive and fast winds of Wolf Rayet stars present a serious momentum problem for the line-driven wind theories that are commonly used to explain the fast winds of early type stars. It is perhaps possible for the winds to be driven by lines, if multiple scattering occurs and if there are a sufficient number of lines in the spectrum so that large fraction of the continuum is blocked by line opacity in the winds. Several other mechanisms are discussed, in particular two that rely on strong magnetic fields: a) Alfven wave driven wind models like those recently developed by Hartmann and MacGregor for late type supergiants and b) the ''Fast Magnetic Rotator'' model that was developed by Belcher and MacGregor for the winds from pre-main sequence stars. In either model, large magnetic fields (approximately equal to 10 4 gauss) are required to drive the massive and fast winds of Wolf Rayet stars. Smaller fields might be possible if the multiple scattering line radiation force can be relied on to provide a final acceleration to terminal velocity. (Auth.)

Simulation of the fate of faecal bacteria in estuarine and coastal waters based on a fractionated sediment transport model

Science.gov (United States)

Yang, Chen; Liu, Ying

2017-08-01

A two-dimensional depth-integrated numerical model is refined in this paper to simulate the hydrodynamics, graded sediment transport process and the fate of faecal bacteria in estuarine and coastal waters. The sediment mixture is divided into several fractions according to the grain size. A bed evolution model is adopted to simulate the processes of the bed elevation change and sediment grain size sorting. The faecal bacteria transport equation includes enhanced source and sink terms to represent bacterial kinetic transformation and disappearance or reappearance due to sediment deposition or re-suspension. A novel partition ratio and dynamic decay rates of faecal bacteria are adopted in the numerical model. The model has been applied to the turbid water environment in the Bristol Channel and Severn estuary, UK. The predictions by the present model are compared with field data and those by non-fractionated model.

Treatment of Highly Turbid Water by Polyaluminum Ferric Chloride (PAFCL

Directory of Open Access Journals (Sweden)

Fazel Fazel Mohammadi-Moghaddam

2015-10-01

Full Text Available Background & Aims of the Study: In some situation like rainfall seasons raw water become very turbid so it affected the water treatment plant processes and quality of produced water. Treatment of very high turbid water has some concerns like precursors for disinfection by-products and very loading rate of particle on filter's media and consequently increases in water consumption for filter backwash. This paper investigates the performance of a composite inorganic polymer of aluminium and ferric salt, Polyaluminium ferric chloride (PAFCl, for the removal of turbidity, color and natural organic matter (NOM from high turbid water. Materials and Methods: Experiments were carried out by Jar test experiment by synthetic water samples with 250 and 500 NTU turbidity that prepared in laboratory. Results: The results of conventional jar test showed that the optimum pH for coagulation of water sample was 7.5 to 8 and optimum dosage of the coagulant was 10 mg/L. Removal efficiency of turbidity, color and UV adsorbent at 254 nm at optimum dose and pH without filtration was 99.92%, 100% and 80.6% respectively for first sample (250 NTU and 99.95%, 99.49% and 84.77 for second sample (500 NTU respectively. Conclusion: It concluded that polyaluminium ferric chloride has a very good efficiency for the removal of turbidity, color and organic matter in high turbid water. Also it can be select as a coagulant for high turbid water and some waste water from water treatment plant like filter backwash water.

Wind erosion processes and control

Science.gov (United States)

Wind erosion continues to threaten the sustainability of our nations' soil, air, and water resources. To effectively apply conservation systems to prevent wind driven soil loss, an understanding of the fundamental processes of wind erosion is necessary so that land managers can better recognize the ...

Wind-Driven Ecological Flow Regimes Downstream from Hydropower Dams

Science.gov (United States)

Kern, J.; Characklis, G. W.

2012-12-01

Conventional hydropower can be turned on and off quicker and less expensively than thermal generation (coal, nuclear, or natural gas). These advantages enable hydropower utilities to respond to rapid fluctuations in energy supply and demand. More recently, a growing renewable energy sector has underlined the need for flexible generation capacity that can complement intermittent renewable resources such as wind power. While wind power entails lower variable costs than other types of generation, incorporating it into electric power systems can be problematic. Due to variable and unpredictable wind speeds, wind power is difficult to schedule and must be used when available. As a result, integrating large amounts of wind power into the grid may result in atypical, swiftly changing demand patterns for other forms of generation, placing a premium on sources that can be rapidly ramped up and down. Moreover, uncertainty in wind power forecasts will stipulate increased levels of 'reserve' generation capacity that can respond quickly if real-time wind supply is less than expected. These changes could create new hourly price dynamics for energy and reserves, altering the short-term financial signals that hydroelectric dam operators use to schedule water releases. Traditionally, hourly stream flow patterns below hydropower dams have corresponded in a very predictable manner to electricity demand, whose primary factors are weather (hourly temperature) and economic activity (workday hours). Wind power integration has the potential to yield more variable, less predictable flows at hydro dams, flows that at times could resemble reciprocal wind patterns. An existing body of research explores the impacts of standard, demand-following hydroelectric dams on downstream ecological flows; but weighing the benefits of increased reliance on wind power against further impacts to ecological flows may be a novel challenge for the environmental community. As a preliminary step in meeting this

Using turbidity for designing water networks.

Science.gov (United States)

Castaño, J A; Higuita, J C

2016-05-01

Some methods to design water networks with minimum fresh water consumption are based on the selection of a key contaminant. In most of these "single contaminant methods", a maximum allowable concentration of contaminants must be established in water demands and water sources. Turbidity is not a contaminant concentration but is a property that represents the "sum" of other contaminants, with the advantage that it can be cheaper and easily measured than biological oxygen demand, chemical oxygen demand, suspended solids, dissolved solids, among others. The objective of this paper is to demonstrate that turbidity can be used directly in the design of water networks just like any other contaminant concentration. A mathematical demonstration is presented and in order to validate the mathematical results, the design of a water network for a guava fudge production process is performed. The material recovery pinch diagram and nearest neighbors algorithm were used for the design of the water network. Nevertheless, this water network could be designed using other single contaminant methodologies. The maximum error between the expected and the real turbidity values in the water network was 3.3%. These results corroborate the usefulness of turbidity in the design of water networks. Copyright © 2016 Elsevier Ltd. All rights reserved.

Electronic Power Transformer Control Strategy in Wind Energy Conversion Systems for Low Voltage Ride-through Capability Enhancement of Directly Driven Wind Turbines with Permanent Magnet Synchronous Generators (D-PMSGs

Directory of Open Access Journals (Sweden)

Hui Huang

2014-11-01

Full Text Available This paper investigates the use of an Electronic Power Transformer (EPT incorporated with an energy storage system to smooth the wind power fluctuations and enhance the low voltage ride-through (LVRT capability of directly driven wind turbines with permanent magnet synchronous generators (D-PMSGs. The decoupled control schemes of the system, including the grid side converter control scheme, generator side converter control scheme and the control scheme of the energy storage system, are presented in detail. Under normal operating conditions, the energy storage system absorbs the high frequency component of the D-PMSG output power to smooth the wind power fluctuations. Under grid fault conditions, the energy storage system absorbs the redundant power, which could not be transferred to the grid by the EPT, to help the D-PMSG to ride through low voltage conditions. This coordinated control strategy is validated by simulation studies using MATLAB/Simulink. With the proposed control strategy, the output wind power quality is improved and the D-PMSG can ride through severe grid fault conditions.

Tidal variations in the Sundarbans estuarine system, India

Digital Repository Service at National Institute of Oceanography (India)

Chatterjee, M.; Shankar, D.; Sen, G.K.; Sanyal, P.; Sundar, D.; Michael, G.S.; Chatterjee, A.; Amol, P.; Mukherjee, D.; Suprit, K.; Mukherjee, A.; Vijith, V.; Chatterjee, S.; Basu, A.; Das, M.; Chakraborti, S.; Kalla, A.; Misra, S.K.; Mukhopadhyay, S.; Mandal, G.; Sarkar, K.

Situated in the eastern coastal state of West Bengal, the Sundarbans Estuarine System (SES) is India’s largest monsoonal, macro-tidal delta-front estuarine system. It comprises the southernmost part of the Indian portion of the Ganga...

Atmospheric turbidity and the diffuse irradiance in Lagos, Nigeria

International Nuclear Information System (INIS)

Maduekwe, A.A.L.; Chendo, M.A.C.

1994-06-01

The relationships between the total hemispherical irradiance reaching the earth surface in Lagos, Nigeria and the turbidity coefficients at two wavelengths namely λ(500) and λ(880) measured with a Volz sun photometer have been investigated. Using simple piecewise linear regression relationships between the atmospheric turbidity using Angstrom turbidity coefficients and the diffuse components of solar radiation are presented. (author). 18 refs, 11 figs, 3 tabs

77 FR 60107 - National Estuarine Research Reserve System

Science.gov (United States)

2012-10-02

... awareness and community involvement in stewardship, incompatible use by visitors, and ecological impacts of... DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Estuarine Research Reserve System AGENCY: Estuarine Reserves Division, Office of Ocean and Coastal Resource Management...

Anti-cyclonic circulation driven by the estuarine circulation in a gulf type ROFI

Science.gov (United States)

Fujiwara, T.; Sanford, L. P.; Nakatsuji, K.; Sugiyama, Y.

1997-08-01

Baroclinic residual circulation processes are examined in gulf type Regions Of Freshwater Influence (ROFIs), which have large rivers discharging into a rounded head wider than the Rossby internal deformation radius. Theoretical and observational investigations concentrate on Ise Bay, Japan, with supporting data from Osaka Bay and Tokyo Bay. Simplified analytical solutions are derived to describe the primary features of the circulation. Three dimensional residual current data collected using moored current meters and shipboard acoustic doppler current profilers (ADCPs), satellite imagery and density structure data observed using STDs, are presented for comparison to the theoretical predictions. There are three key points to understanding the resulting circulation in gulf type ROFIs. First, there are likely to be three distinct water masses: the river plume, a brackish upper layer, and a higher salinity lower layer. Second, baroclinic processes in gulf type ROFIs are influenced by the Earth's rotation at first order. Residual currents are quasi-geostrophic and potential vorticity is approximately conserved. Third, the combined effects of a classical longitudinal estuarine circulation and the Earth's rotation are both necessary to produce the resulting circulation. Anti-cyclonic vorticity is generated in the upper layer by the horizontal divergence associated with upward entrainment, which is part of the estuarine circulation. The interaction between anti-cyclonic vorticity and horizontal divergence results in two regions of qualitatively different circulation, with gyre-like circulation near the bay head and uniformly seaward anti-cyclonicly sheared flow further towards the mouth. The stagnation point separating the two regions is closer to (further away from) the bay head for stronger (weaker) horizontal divergence, respectively. The vorticity and spin-up time of this circulation are-(ƒ-ω 1)/2 and h/2w 0, respectively, where ƒ is the Coriolis parameter, ω 1 is

Removal of Cu2+ and turbidity from wastewater by mercaptoacetyl chitosan.

Science.gov (United States)

Chang, Qing; Zhang, Min; Wang, Jinxi

2009-09-30

A macromolecule heavy metal flocculant mercaptoacetyl chitosan (MAC) was prepared by reacting chitosan with mercaptoacetic acid. In preliminary experiments, the flocculation performance of MAC was evaluated by using wastewater containing Cu(2+) or/and turbidity. Some factors which affect the removal of Cu(2+) and turbidity were also studied. The experimental results showed that: (1) MAC can remove both Cu(2+) and turbidity from wastewater. The removal efficiency of Cu(2+) by using MAC combined with hydrolyzed polyacrylamide is higher than that by only using MAC, the removal efficiency of Cu(2+) reaches above 98%; (2) when water sample containing not only Cu(2+) but also turbidity-causing substance, the removal efficiency of both Cu(2+) and turbidity will be promoted by the cooperation effect of each other, the residual concentration of Cu(2+) reaches below 0.5 mg L(-1) and the turbidity reaches below 3NTU, Cu(2+) is more easily removed by MAC when turbidity is higher; (3) the removal efficiency of Cu(2+) increases with the increase in pH value, contrarily removal efficiency of turbidity decreases with the increase in pH value.

The combined effect of wind and rain on interrill erosion processes

International Nuclear Information System (INIS)

Erpul, G.; Gabriels, D.; Norton, L.D.

2004-01-01

Wind-driven rain is described as raindrops falling through a wind field at an angle from vertical under the effects of both gravitational and drag forces. Wind-driven raindrops gain some degree of horizontal velocity and strike the soil surface with an angle deviated from vertical. Additionally, the distribution and intensity of rainfall on sloping surfaces differs depending on wind direction and velocity. The changes in raindrop trajectory and frequency with wind velocity and direction can have significant effects on rain splash detachment process. The resultant impact velocity, impact angle, and impact frequency of raindrops determine the magnitude of rain splash detachment by wind-driven rain. This differs from the detachment process by windless rain, in which a straight-line trajectory of raindrops and accordingly greatest rainfall intensity for a given rain are implicitly assumed. Wind, as well as slope and overland flow, is another possible factor capable of transporting detached particles by raindrop impact. Once soil particles are entrained in the splash droplets that have risen into the air by raindrop impact, wind velocity gradient will transport these particles. Obviously, in addition to its role in the rain splash detachment process, the wind accompanying rain is an important consideration in the rain splash transport process, which can cause a net transportation in wind direction. In wind-driven rains, wind velocity and direction is expected to affect not only rain splash detachment and transport processes but also shallow flow sediment transport induced by raindrop impacts with an angle on flow and the rain splash trajectories of soil particles within flow. Under wind-driven rain, the interrill transport process is a combined work of both rain splash sediment transport and raindrop-impacted shallow flow sediment transport. The rain splash process acts alone until runoff occurs, and net soil transport is caused by wind. As soon as runoff starts, the

Interactions between waves, sediment, and turbulence on a shallow estuarine mudflat

Science.gov (United States)

MacVean, Lissa J.; Lacy, Jessica R.

2014-01-01

Measurements were collected on a shallow estuarine mudflat in northern San Francisco Bay to examine the physical processes controlling waves, turbulence, sediment resuspension, and their interactions. Tides alone forced weak to moderate currents of 10–30 cm s-1 in depths of 0–3 m, and maintained a background suspension of 30–50 mg L21 of fine sediment. In the presence of wind waves, bottom orbital velocities spanned 20–30 cm s-1, suspended-sediment concentrations (SSC) at 15 and 30 cm above the bed (cmab) increased by 1–2 orders of magnitude, and vertical gradients in SSC were strong enough to produce turbulence-limiting stratification, with gradient Richardson numbers exceeding 0.25. Simultaneously, turbulent

INJECTION OF PLASMA INTO THE NASCENT SOLAR WIND VIA RECONNECTION DRIVEN BY SUPERGRANULAR ADVECTION

International Nuclear Information System (INIS)

Yang Liping; He Jiansen; Tu Chuanyi; Chen Wenlei; Zhang Lei; Wang Linghua; Yan Limei; Peter, Hardi; Marsch, Eckart; Feng, Xueshang

2013-01-01

To understand the origin of the solar wind is one of the key research topics in modern solar and heliospheric physics. Previous solar wind models assumed that plasma flows outward along a steady magnetic flux tube that reaches continuously from the photosphere through the chromosphere into the corona. Inspired by more recent comprehensive observations, Tu et al. suggested a new scenario for the origin of the solar wind, in which it flows out in a magnetically open coronal funnel and mass is provided to the funnel by small-scale side loops. Thus mass is supplied by means of magnetic reconnection that is driven by supergranular convection. To validate this scenario and simulate the processes involved, a 2.5 dimensional (2.5D) numerical MHD model is established in the present paper. In our simulation a closed loop moves toward an open funnel, which has opposite polarity and is located at the edge of a supergranulation cell, and magnetic reconnection is triggered and continues while gradually opening up one half of the closed loop. Its other half connects with the root of the open funnel and forms a new closed loop which is submerged by a reconnection plasma stream flowing downward. Thus we find that the outflowing plasma in the newly reconnected funnel originates not only from the upward reconnection flow but also from the high-pressure leg of the originally closed loop. This implies an efficient supply of mass from the dense loop to the dilute funnel. The mass flux of the outflow released from the funnel considered in our study is calculated to be appropriate for providing the mass flux at the coronal base of the solar wind, though additional heating and acceleration mechanisms are necessary to keep the velocity at the higher location. Our numerical model demonstrates that in the funnel the mass for the solar wind may be supplied from adjacent closed loops via magnetic reconnection as well as directly from the footpoints of open funnels.

Field studies of estuarine turbidity under different freshwater flow conditions, Kaipara River, New Zealand

Science.gov (United States)

Mitchell, Steven B.; Green, Malcolm O.; MacDonald, Iain T.; Pritchard, Mark

2017-11-01

We present a first interpretation of three days of measurements made in 2013 from the tidal reaches of the Kaipara River (New Zealand) under both low and high freshwater inputs and a neap tidal cycle. During the first day, we occupied two stations that were approximately 6 km apart in a tidal reach that runs for 25 km from the river mouth to the upstream limit of tidal influence. During the second day, longitudinal surveys were conducted over a distance of 6 km centred on the upstream station. The data reveal a turbidity maximum in the form of a high-concentration 'plug' of suspended mud that was advected downstream on the ebbing tide past the upper (HB) measurement station and which exchanged sediment with the seabed by settling at low slack water and by resuspension in the early flooding tide. The data suggest that fine sediment is transported landwards and trapped in the upper part of the tidal reach under these low-flow conditions. On the third day of measurements we repeated the experiments of the first day but later in the year, for a much higher freshwater flow. This interpretation of our data set highlights the potential contribution of a range of processes to the generation of the observed suspended-sediment signals, including resuspension of local bed sediment, advection by the tidal current, settling of suspended sediment over a long timescale compared to the advection timescale, advection of longitudinal gradients in suspended sediment, and suppression of vertical mixing by density stratification of the water column. The level of temporal and spatial detail afforded by these measurements allows a much clearer understanding of the timing and importance of vertical stratification on the transport of suspended particulate matter than is generally possible using fixed-point sensors.

Insolation and turbidity measurements at Hanford

International Nuclear Information System (INIS)

Laulainen, N.S.; Kleckner, E.W.; Michalsky, J.J.; Thorp, J.M.

1979-01-01

From observations obtained at the Rattlesnake Observatory and the Hanford Meteorological Station, the redistribution of solar radiation as a result of aerosols in the lowest 1 km of the earth's atmosphere has been examined using several types of solar radiation measuring instruments. Large turbidity excursions are observed with high values associated with stagnant air masses and low values associated with frontal passage. Turbidities show variations in color dependence that arise because of changes in particle size distribution

Influence of Waves and Tides on Upper Slope Turbidity Currents and their Deposits: An Outcrop and Laboratory Study

Science.gov (United States)

Daniller-Varghese, M. S.; Smith, E.; Mohrig, D. C.; Goudge, T. A.; Hassenruck-Gudipati, H. J.; Koo, W. M.; Mason, J.; Swartz, J. M.; Kim, J.

2017-12-01

Research on interactions of turbidity currents with waves and tides highlight both their importance and complexity. The Elkton Siltstone at Cape Arago, Oregon, USA, preserves rhythmically bedded deposits that we interpret as the product of tidally modified hyperpycnal flows under the influence of water-surface waves. Evidence for the interpretation of tidal influence is taken from couplet thickness measurements consistent with semidiurnal tides arranged into monthly cycles. These deposits were likely sourced from suspended-sediment laden river plumes; thinner, finer-grained beds represent deposition during flood tide, and thicker, coarser-grained beds represent deposition during ebb tide. Sedimentary structures within the rhythmites change from proximal to distal sections, but both sections preserve combined-flow bedforms within the beds, implying wave influence. Our paleo-topographic reconstruction has the proximal section located immediately down-dip of the shelf slope-break and the distal section located 1.5km further offshore in 125m greater water depth. We present experimental results from wave-influenced turbidity currents calling into question the interpretation that combined-flow bedforms necessarily require deposition at or above paleo-wave base. Turbidity currents composed of quartz silt and very fine sand were released into a 10m long, 1.2m deep tank. Currents ran down a 9-degree ramp with a motor driven wave-maker positioned at the distal end of the tank. The currents interacted with the wave field as they travelled downslope into deeper water. While oscillatory velocities measured within the wave-influenced turbidity currents decreased with distance downslope, the maximum oscillatory velocities measured in the combined-flow currents at depth were five to six times larger than those measured under a wave field without turbidity currents. These results suggest that combined-flow turbidity currents can transmit oscillating-flow signals beneath the

Beyond Rating Curves: Time Series Models for in-Stream Turbidity Prediction

Science.gov (United States)

Wang, L.; Mukundan, R.; Zion, M.; Pierson, D. C.

2012-12-01

The New York City Department of Environmental Protection (DEP) manages New York City's water supply, which is comprised of over 20 reservoirs and supplies over 1 billion gallons of water per day to more than 9 million customers. DEP's "West of Hudson" reservoirs located in the Catskill Mountains are unfiltered per a renewable filtration avoidance determination granted by the EPA. While water quality is usually pristine, high volume storm events occasionally cause the reservoirs to become highly turbid. A logical strategy for turbidity control is to temporarily remove the turbid reservoirs from service. While effective in limiting delivery of turbid water and reducing the need for in-reservoir alum flocculation, this strategy runs the risk of negatively impacting water supply reliability. Thus, it is advantageous for DEP to understand how long a particular turbidity event will affect their system. In order to understand the duration, intensity and total load of a turbidity event, predictions of future in-stream turbidity values are important. Traditionally, turbidity predictions have been carried out by applying streamflow observations/forecasts to a flow-turbidity rating curve. However, predictions from rating curves are often inaccurate due to inter- and intra-event variability in flow-turbidity relationships. Predictions can be improved by applying an autoregressive moving average (ARMA) time series model in combination with a traditional rating curve. Since 2003, DEP and the Upstate Freshwater Institute have compiled a relatively consistent set of 15-minute turbidity observations at various locations on Esopus Creek above Ashokan Reservoir. Using daily averages of this data and streamflow observations at nearby USGS gauges, flow-turbidity rating curves were developed via linear regression. Time series analysis revealed that the linear regression residuals may be represented using an ARMA(1,2) process. Based on this information, flow-turbidity regressions with

Turbidity-controlled suspended sediment sampling for runoff-event load estimation

Science.gov (United States)

Jack Lewis

1996-01-01

Abstract - For estimating suspended sediment concentration (SSC) in rivers, turbidity is generally a much better predictor than water discharge. Although it is now possible to collect continuous turbidity data even at remote sites, sediment sampling and load estimation are still conventionally based on discharge. With frequent calibration the relation of turbidity to...

Implementation guide for turbidity threshold sampling: principles, procedures, and analysis

Science.gov (United States)

Jack Lewis; Rand Eads

2009-01-01

Turbidity Threshold Sampling uses real-time turbidity and river stage information to automatically collect water quality samples for estimating suspended sediment loads. The system uses a programmable data logger in conjunction with a stage measurement device, a turbidity sensor, and a pumping sampler. Specialized software enables the user to control the sampling...

78 FR 50038 - National Estuarine Research Reserve System

Science.gov (United States)

2013-08-16

....33(c), the revised plan meets the reserve's requirements for compliance. The Wells Reserve Management... Reserve System AGENCY: Estuarine Reserves Division, Office of Ocean and Coastal Resource Management.... ACTION: Notice of Public Comment Period for the Wells, Maine National Estuarine Research Reserve...

Influence of Wind Strength and Duration on Relative Hypoxia Reductions by Opposite Wind Directions in an Estuary with an Asymmetric Channel

Directory of Open Access Journals (Sweden)

Ping Wang

2016-09-01

Full Text Available Computer model experiments are applied to analyze hypoxia reductions for opposing wind directions under various speeds and durations in the north–south oriented, two-layer-circulated Chesapeake estuary. Wind’s role in destratification is the main mechanism in short-term reduction of hypoxia. Hypoxia can also be reduced by wind-enhanced estuarine circulation associated with winds that have down-estuary straining components that promote bottom-returned oxygen-rich seawater intrusion. The up-bay-ward along-channel component of straining by the southerly or easterly wind induces greater destratification than the down-bay-ward straining by the opposite wind direction, i.e., northerly or westerly winds. While under the modulation of the west-skewed asymmetric cross-channel bathymetry in the Bay’s hypoxic zone, the westward cross-channel straining by easterly or northerly winds causes greater destratification than its opposite wind direction. The wind-induced cross-channel circulation can be completed much more rapidly than the wind-induced along-channel circulation, and the former is usually more effective than the latter in destratification and hypoxia reduction in an early wind period. The relative importance of cross-channel versus along-channel circulation for a particular wind direction can change with wind speed and duration. The existence of month-long prevailing unidirectional winds in the Chesapeake is explored, and the relative hypoxia reductions among different prevailing directions are analyzed. Scenarios of wind with intermittent calm or reversing directions on an hourly scale are also simulated and compared.

Design of large permanent magnetized synchronous electric machines: Low speed, high torque machines - generator for direct driven wind turbine - motor for rim driven thruster

Energy Technology Data Exchange (ETDEWEB)

Kroevel, Oeystein

2011-02-15

This work presents the design of two prototype permanent magnetized electric machines for two different applications where large permanent magnet machines might be used. Existing technology have been used as the fundament for new design and adapted to new applications, contributing, hopefully, to the development of better and more environmental friendly energy conversion. The first application presented is represented with a prototype made in cooperation with the industry in which a PM-motor is integrated into a propeller unit. Both because of the industrial connection, and the integration between the PM-motor and the propeller, the choices made for the PM-motor are conservative trying to reduce the risk. The direct rim driven thruster prototype includes a surface mounted radial flux permanent magnet machine (SM RFPM) with fractional slot winding with a q around 1. Other engineering features were introduced to make the integration of propeller and motor feasible, but without the PM-machine the thruster would not have reached the performance demand. An important part of the project was to show that the SM RFPM enables this solution, providing high performance with a large air gap. The prototype has been tested in sea, under harsh conditions, and even though the magnets have been exposed directly to sea water and been visible corroded, the electric motor still performs well within the specifications. The second application is represented with a prototype PM-generator for wind turbines. This is an example of a new, very low speed high torque machine. The generator is built to test phenomena regarding concentrated coils, and as opposed to the first application, being a pure academic university project, its success is not connected to its performance, but with the prototype's ability to expose the phenomena in question. The prototype, or laboratory model, of the generator for direct driven wind turbines features SM RFPM with concentrated coils (CC). An opportunity

Estuarine Facies Model Revisited: Conceptual Model of Estuarine Sediment Dynamics During Non-Equilibrium Conditions

Science.gov (United States)

Elliott, E. A.; Rodriguez, A. B.; McKee, B. A.

2017-12-01

Traditional models of estuarine systems show deposition occurs primarily within the central basin. There, accommodation space is high within the deep central valley, which is below regional wave base and where current energy is presumed to reach a relative minimum, promoting direct deposition of cohesive sediment and minimizing erosion. However, these models often reflect long-term (decadal-millennial) timescales, where accumulation rates are in relative equilibrium with the rate of relative sea-level rise, and lack the resolution to capture shorter term changes in sediment deposition and erosion within the central estuary. This work presents a conceptual model for estuarine sedimentation during non-equilibrium conditions, where high-energy inputs to the system reach a relative maximum in the central basin, resulting in temporary deposition and/or remobilization over sub-annual to annual timescales. As an example, we present a case study of Core Sound, NC, a lagoonal estuarine system where the regional base-level has been reached, and sediment deposition, resuspension and bypassing is largely a result of non-equilibrium, high-energy events. Utilizing a 465 cm-long sediment core from a mini-basin located between Core Sound and the continental shelf, a 40-year sub-annual chronology was developed for the system, with sediment accumulation rates (SAR) interpolated to a monthly basis over the 40-year record. This study links erosional processes in the estuary directly with sediment flux to the continental shelf, taking advantage of the highly efficient sediment trapping capability of the mini-basin. The SAR record indicates high variation in the estuarine sediment supply, with peaks in the SAR record at a recurrence interval of 1 year (+/- 0.25). This record has been compared to historical storm influence for the area. Through this multi-decadal record, sediment flushing events occur at a much more frequent interval than previously thought (i.e. annual rather than

Black-hole driven winds

International Nuclear Information System (INIS)

Punsly, B.M.

1988-01-01

This dissertation is a study of the physical mechanism that allows a large scale magnetic field to torque a rapidly rotating, supermassive black hole. This is an interesting problem as it has been conjectured that rapidly rotating black holes are the central engines that power the observed extragalactic double radio sources. Axisymmetric solutions of the curved space-time version of Maxwell's equations in the vacuum do not torque black holes. Plasma must be introduced for the hole to mechanically couple to the field. The dynamical aspect of rotating black holes that couples the magnetic field to the hole is the following. A rotating black hole forces the external geometry of space-time to rotate (the dragging of inertial frames). Inside of the stationary limit surface, the ergosphere, all physical particle trajectories must appear to rotate in the same direction as the black hole as viewed by the stationary observers at asymptotic infinity. In the text, it is demonstrated how plasma that is created on field lines that thread both the ergosphere and the equatorial plane will be pulled by gravity toward the equator. By the aforementioned properties of the ergosphere, the disk must rotate. Consequently, the disk acts like a unipolar generator. It drives a global current system that supports the toroidal magnetic field in an outgoing, magnetically dominated wind. This wind carries energy (mainly in the form of Poynting flux) and angular momentum towards infinity. The spin down of the black hole is the ultimate source of this energy and angular momentum flux

Maximum power extraction under different vector-control schemes and grid-synchronization strategy of a wind-driven Brushless Doubly-Fed Reluctance Generator.

Science.gov (United States)

Mousa, Mohamed G; Allam, S M; Rashad, Essam M

2018-01-01

This paper proposes an advanced strategy to synchronize the wind-driven Brushless Doubly-Fed Reluctance Generator (BDFRG) to the grid-side terminals. The proposed strategy depends mainly upon determining the electrical angle of the grid voltage, θ v and using the same transformation matrix of both the power winding and grid sides to ensure that the generated power-winding voltage has the same phase-sequence of the grid-side voltage. On the other hand, the paper proposes a vector-control (power-winding flux orientation) technique for maximum wind-power extraction under two schemes summarized as; unity power-factor operation and minimum converter-current. Moreover, a soft-starting method is suggested to avoid the employed converter over-current. The first control scheme is achieved by adjusting the command power-winding reactive power at zero for a unity power-factor operation. However, the second scheme depends on setting the command d-axis control-winding current at zero to maximize the ratio of the generator electromagnetic-torque per the converter current. This enables the system to get a certain command torque under minimum converter current. A sample of the obtained simulation and experimental results is presented to check the effectiveness of the proposed control strategies. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

The differences between storms driven by helmet streamer CIRs and storms driven by pseudostreamer CIRs

OpenAIRE

Borovsky, Joseph E.; Denton, Michael

2013-01-01

A corotating interaction region (CIR) is formed when fast coronal hole origin solar wind overtakes slow solar wind and forms a region of compressed plasma and magnetic field. The slow wind upstream of the coronal hole fast wind can be either of helmet streamer origin or pseudostreamer origin. For a collection of 125 CIR-driven geomagnetic storms, the slow wind ahead of each CIR is examined; for those storm not containing ejecta, each CIR is categorized as a helmet streamer CIR (74 of the 125 ...

Dissolved Vanillin as Tracer for Estuarine Lignin Conversion

Science.gov (United States)

Edelkraut, F.

1996-12-01

Lignin is produced only by vascular plants and therefore can be used as a tracer for terrestrial organic carbon input to the estuarine and marine environments. Lignin measurements have been done by analyses of the oxidation products such as vanillin or 4-hydroxybenzaldehyde. In the Elbe Estuary, free dissolved vanillin was analysed in order to test whether such measurements yield information on terrestrial carbon inputs into the Estuary and on the vanillin derived from lignin oxidation. In the period 1990-1992, concentrations of dissolved vanillin in the Elbe ranged from 0 to 60 μ g l -1(mean: 8 μg l -1). Higher values were found in areas of increased microbial activity such as the turbidity zone and the river mouth where the water chemistry is influenced by large tidal flats. No correlation was found between dissolved vanillin and suspended matter concentrations, although lignin is normally associated with suspended particulate matter, nor was a covariance seen between dissolved vanillin and the terrestrial carbon inputs into the Estuary. Apparently, biological conversion of lignin was faster than the transport processes, and local sources were more dominant for the vanillin concentration than riverine sources. The dissolved vanillin turnover was fast and, consequently, a significant amount of lignin may be converted within an estuary. In sediments from the Estuary, the concentrations of dissolved vanillin were similar to those found in the water phase and showed no clear vertical profile. The sediment is unlikely to be the source for vanillin.

Dynamic imaging through turbid media based on digital holography.

Science.gov (United States)

Li, Shiping; Zhong, Jingang

2014-03-01

Imaging through turbid media using visible or IR light instead of harmful x ray is still a challenging problem, especially in dynamic imaging. A method of dynamic imaging through turbid media using digital holography is presented. In order to match the coherence length between the dynamic object wave and the reference wave, a cw laser is used. To solve the problem of difficult focusing in imaging through turbid media, an autofocus technology is applied. To further enhance the image contrast, a spatial filtering technique is used. A description of digital holography and experiments of imaging the objects hidden in turbid media are presented. The experimental result shows that dynamic images of the objects can be achieved by the use of digital holography.

A contribution to understanding the turbidity behaviour in an Amazon floodplain

OpenAIRE

Alcântara, E.; Novo, E.; Stech, J.; Lorenzzetti, J.; Barbosa, C.; Assireu, A.; Souza, A.

2010-01-01

Observations of turbidity provide quantitative information about water quality. However, the number of available in situ measurements for water quality determination is usually limited in time and space. Here, we present an analysis of the temporal and spatial variability of the turbidity of an Amazon floodplain lake using two approaches: (1) wavelet analysis of a turbidity time series measured by an automatic monitoring system, which should be improved/simplified, and (2) turbidity samples m...

High Turbidity Solis Clear Sky Model: Development and Validation

Directory of Open Access Journals (Sweden)

Pierre Ineichen

2018-03-01

Full Text Available The Solis clear sky model is a spectral scheme based on radiative transfer calculations and the Lambert–Beer relation. Its broadband version is a simplified fast analytical version; it is limited to broadband aerosol optical depths lower than 0.45, which is a weakness when applied in countries with very high turbidity such as China or India. In order to extend the use of the original simplified version of the model for high turbidity values, we developed a new version of the broadband Solis model based on radiative transfer calculations, valid for turbidity values up to 7, for the three components, global, beam, and diffuse, and for the four aerosol types defined by Shettle and Fenn. A validation of low turbidity data acquired in Geneva shows slightly better results than the previous version. On data acquired at sites presenting higher turbidity data, the bias stays within ±4% for the beam and the global irradiances, and the standard deviation around 5% for clean and stable condition data and around 12% for questionable data and variable sky conditions.

Performance Analysis of a Wind Turbine Driven Swash Plate Pump for Large Scale Offshore Applications

International Nuclear Information System (INIS)

Buhagiar, D; Sant, T

2014-01-01

This paper deals with the performance modelling and analysis of offshore wind turbine-driven hydraulic pumps. The concept consists of an open loop hydraulic system with the rotor main shaft directly coupled to a swash plate pump to supply pressurised sea water. A mathematical model is derived to cater for the steady state behaviour of entire system. A simplified model for the pump is implemented together with different control scheme options for regulating the rotor shaft power. A new control scheme is investigated, based on the combined use of hydraulic pressure and pitch control. Using a steady-state analysis, the study shows how the adoption of alternative control schemes in a the wind turbine-hydraulic pump system may result in higher energy yields than those from a conventional system with an electrical generator and standard pitch control for power regulation. This is in particular the case with the new control scheme investigated in this study that is based on the combined use of pressure and rotor blade pitch control

Conservation Priority Index for Estuarine Fish (COPIEF)

Science.gov (United States)

Branco, Paulo; Costa, José Lino; Raposo de Almeida, Pedro

2008-12-01

Public awareness regarding environmental issues has increased in recent decades. The increasing number of impact assessment studies, management and conservation plans, as well as ecological monitoring studies, demand new and more efficient techniques. Indices are an important tool to aid biologists in these studies and should allow an easier comprehension of the data by managers, decision-makers and the general public. This study presents the first multi-metrical index able to establish a hierarchical ordination of the conservation priority of the estuarine fish species using 72 species from 16 estuarine systems (W and S coasts of Portugal). The index is composed of 10 metrics, comprising species life traits, distribution and population trends. The information needed to score each metric was gathered from the published literature and the index validation was done by external means. This methodology allowed the definition of those fish species most in need of conservation planning, and those less prone to extinction in Portuguese estuarine systems. The proposed index fills a gap in our knowledge and provides a useful tool to the scientific community and to the decision-makers, being a breakthrough in the field of conservation planning of estuarine fish species.

Turbidity of mouthrinsed water as a screening index for oral malodor.

Science.gov (United States)

Ueno, Masayuki; Takeuchi, Susumu; Samnieng, Patcharaphol; Morishima, Seiji; Shinada, Kayoko; Kawaguchi, Yoko

2013-08-01

The objectives of this research were to examine the relationship between turbidity of mouthrinsed water and oral malodor, and to evaluate whether the turbidity could be used to screen oral malodor. The subjects were 165 oral malodor patients. Gas chromatography and organoleptic test (OT) were used for oral malodor measurement. Oral examination along with collection of saliva and quantification of bacteria was conducted. Turbidity of mouthrinsed water was measured with turbidimeter. Logistic regression with oral malodor status by OT as the dependent variable and receiver operating characteristic (ROC) analysis were performed. Turbidity had a significant association with oral malodor status. In addition, ROC analysis showed that the turbidity had an ability to screen for presence or absence of oral malodor. Turbidity could reflect or represent other influential variables of oral malodor and may be useful as a screening method for oral malodor. Copyright © 2013 Elsevier Inc. All rights reserved.

Developmental plasticity in vision and behavior may help guppies overcome increased turbidity.

Science.gov (United States)

Ehlman, Sean M; Sandkam, Benjamin A; Breden, Felix; Sih, Andrew

2015-12-01

Increasing turbidity in streams and rivers near human activity is cause for environmental concern, as the ability of aquatic organisms to use visual information declines. To investigate how some organisms might be able to developmentally compensate for increasing turbidity, we reared guppies (Poecilia reticulata) in either clear or turbid water. We assessed the effects of developmental treatments on adult behavior and aspects of the visual system by testing fish from both developmental treatments in turbid and clear water. We found a strong interactive effect of rearing and assay conditions: fish reared in clear water tended to decrease activity in turbid water, whereas fish reared in turbid water tended to increase activity in turbid water. Guppies from all treatments decreased activity when exposed to a predator. To measure plasticity in the visual system, we quantified treatment differences in opsin gene expression of individuals. We detected a shift from mid-wave-sensitive opsins to long wave-sensitive opsins for guppies reared in turbid water. Since long-wavelength sensitivity is important in motion detection, this shift likely allows guppies to salvage motion-detecting abilities when visual information is obscured in turbid water. Our results demonstrate the importance of developmental plasticity in responses of organisms to rapidly changing environments.

Turbidity-controlled sampling for suspended sediment load estimation

Science.gov (United States)

Jack Lewis

2003-01-01

Abstract - Automated data collection is essential to effectively measure suspended sediment loads in storm events, particularly in small basins. Continuous turbidity measurements can be used, along with discharge, in an automated system that makes real-time sampling decisions to facilitate sediment load estimation. The Turbidity Threshold Sampling method distributes...

Extending the turbidity record: making additional use of continuous data from turbidity, acoustic-Doppler, and laser diffraction instruments and suspended-sediment samples in the Colorado River in Grand Canyon

Science.gov (United States)

Voichick, Nicholas; Topping, David J.

2014-01-01

Turbidity is a measure of the scattering and absorption of light in water, which in rivers is primarily caused by particles, usually sediment, suspended in the water. Turbidity varies significantly with differences in the design of the instrument measuring turbidity, a point that is illustrated in this study by side-by-side comparisons of two different models of instruments. Turbidity also varies with changes in the physical parameters of the particles in the water, such as concentration, grain size, grain shape, and color. A turbidity instrument that is commonly used for continuous monitoring of rivers has a light source in the near-infrared range (860±30 nanometers) and a detector oriented 90 degrees from the incident light path. This type of optical turbidity instrument has a limited measurement range (depending on pathlength) that is unable to capture the high turbidity levels of rivers that carry high suspended-sediment loads. The Colorado River in Grand Canyon is one such river, in which approximately 60 percent of the range in suspended-sediment concentration during the study period had unmeasurable turbidity using this type of optical instrument. Although some optical turbidimeters using backscatter or other techniques can measure higher concentrations of suspended sediment than the models used in this study, the maximum turbidity measurable using these other turbidimeters may still be exceeded in conditions of especially high concentrations of suspended silt and clay. In Grand Canyon, the existing optical turbidity instruments remain in use in part to provide consistency over time as new techniques are investigated. As a result, during these periods of high suspended-sediment concentration, turbidity values that could not be measured with the optical turbidity instruments were instead estimated from concurrent acoustic attenuation data collected using side-looking acoustic-Doppler profiler (ADP) instruments. Extending the turbidity record to the full

Effect of Canister Movement on Water Turbidity

International Nuclear Information System (INIS)

TRIMBLE, D.J.

2000-01-01

Requirements for evaluating the adherence characteristics of sludge on the fuel stored in the K East Basin and the effect of canister movement on basin water turbidity are documented in Briggs (1996). The results of the sludge adherence testing have been documented (Bergmann 1996). This report documents the results of the canister movement tests. The purpose of the canister movement tests was to characterize water turbidity under controlled canister movements (Briggs 1996). The tests were designed to evaluate methods for minimizing the plumes and controlling water turbidity during fuel movements leading to multi-canister overpack (MCO) loading. It was expected that the test data would provide qualitative visual information for use in the design of the fuel retrieval and water treatment systems. Video recordings of the tests were to be the only information collected

Ocean Wave Simulation Based on Wind Field.

Directory of Open Access Journals (Sweden)

Zhongyi Li

Full Text Available Ocean wave simulation has a wide range of applications in movies, video games and training systems. Wind force is the main energy resource for generating ocean waves, which are the result of the interaction between wind and the ocean surface. While numerous methods to handle simulating oceans and other fluid phenomena have undergone rapid development during the past years in the field of computer graphic, few of them consider to construct ocean surface height field from the perspective of wind force driving ocean waves. We introduce wind force to the construction of the ocean surface height field through applying wind field data and wind-driven wave particles. Continual and realistic ocean waves result from the overlap of wind-driven wave particles, and a strategy was proposed to control these discrete wave particles and simulate an endless ocean surface. The results showed that the new method is capable of obtaining a realistic ocean scene under the influence of wind fields at real time rates.

Performance of alum and assorted coagulants in turbidity removal of muddy water

Science.gov (United States)

Malik, Qasim H.

2018-03-01

Coagulation is a primary and cost effective process in water treatment plants. Under optimum conditions, not only it effectively removes turbidity but also results in reduced sludge volume and subsequently minimizes sludge management costs. Highly turbid water from streams, canals, rivers and rain run offs was run through jar test for turbidity removal. The brown water with 250NTU turbidity when coagulated with alum and assorted coagulants proved that maximum turbidity removal was witnessed using alum dose of 0.25 g/l at ph 6 with a sedimentation time of 30 min.

Wind Extraction for Natural Ventilation

Science.gov (United States)

Fagundes, Tadeu; Yaghoobian, Neda; Kumar, Rajan; Ordonez, Juan

2017-11-01

Due to the depletion of energy resources and the environmental impact of pollution and unsustainable energy resources, energy consumption has become one of the main concerns in our rapidly growing world. Natural ventilation, a traditional method to remove anthropogenic and solar heat gains, proved to be a cost-effective, alternative method to mechanical ventilation. However, while natural ventilation is simple in theory, its detailed design can be a challenge, particularly for wind-driven ventilation, which its performance highly involves the buildings' form, surrounding topography, turbulent flow characteristics, and climate. One of the main challenges with wind-driven natural ventilation schemes is due to the turbulent and unpredictable nature of the wind around the building that impose complex pressure loads on the structure. In practice, these challenges have resulted in founding the natural ventilation mainly on buoyancy (rather than the wind), as the primary force. This study is the initial step for investigating the physical principals of wind extraction over building walls and investigating strategies to reduce the dependence of the wind extraction on the incoming flow characteristics and the target building form.

Effects of Topography-driven Micro-climatology on Evaporation

Science.gov (United States)

Adams, D. D.; Boll, J.; Wagenbrenner, N. S.

2017-12-01

The effects of spatial-temporal variation of climatic conditions on evaporation in micro-climates are not well defined. Current spatially-based remote sensing and modeling for evaporation is limited for high resolutions and complex topographies. We investigated the effect of topography-driven micro-climatology on evaporation supported by field measurements and modeling. Fourteen anemometers and thermometers were installed in intersecting transects over the complex topography of the Cook Agronomy Farm, Pullman, WA. WindNinja was used to create 2-D vector maps based on recorded observations for wind. Spatial analysis of vector maps using ArcGIS was performed for analysis of wind patterns and variation. Based on field measurements, wind speed and direction show consequential variability based on hill-slope location in this complex topography. Wind speed and wind direction varied up to threefold and more than 45 degrees, respectively for a given time interval. The use of existing wind models enables prediction of wind variability over the landscape and subsequently topography-driven evaporation patterns relative to wind. The magnitude of the spatial-temporal variability of wind therefore resulted in variable evaporation rates over the landscape. These variations may contribute to uneven crop development patterns observed during the late growth stages of the agricultural crops at the study location. Use of hill-slope location indexes and appropriate methods for estimating actual evaporation support development of methodologies to better define topography-driven heterogeneity in evaporation. The cumulative effects of spatially-variable climatic factors on evaporation are important to quantify the localized water balance and inform precision farming practices.

Sediment and turbidity associated with offshore dredging increase coral disease prevalence on nearby reefs.

Science.gov (United States)

Pollock, F Joseph; Lamb, Joleah B; Field, Stuart N; Heron, Scott F; Schaffelke, Britta; Shedrawi, George; Bourne, David G; Willis, Bette L

2014-01-01

In recent decades, coral reef ecosystems have declined to the extent that reefs are now threatened globally. While many water quality parameters have been proposed to contribute to reef declines, little evidence exists conclusively linking specific water quality parameters with increased disease prevalence in situ. Here we report evidence from in situ coral health surveys confirming that chronic exposure to dredging-associated sediment plumes significantly increase the prevalence of white syndromes, a devastating group of globally important coral diseases. Coral health surveys were conducted along a dredging-associated sediment plume gradient to assess the relationship between sedimentation, turbidity and coral health. Reefs exposed to the highest number of days under the sediment plume (296 to 347 days) had two-fold higher levels of disease, largely driven by a 2.5-fold increase in white syndromes, and a six-fold increase in other signs of compromised coral health relative to reefs with little or no plume exposure (0 to 9 days). Multivariate modeling and ordination incorporating sediment exposure level, coral community composition and cover, predation and multiple thermal stress indices provided further confirmation that sediment plume exposure level was the main driver of elevated disease and other compromised coral health indicators. This study provides the first evidence linking dredging-associated sedimentation and turbidity with elevated coral disease prevalence in situ. Our results may help to explain observed increases in global coral disease prevalence in recent decades and suggest that minimizing sedimentation and turbidity associated with coastal development will provide an important management tool for controlling coral disease epizootics.

Turbidity data: Hollywood Beach, Florida, January 1990 to April 1992

OpenAIRE

Dompe, Philip E.; Hanes, D. M.

1993-01-01

This data report contains measurements of turbidity obtained near Hollywood, Florida, during the period of January 1990 to April 1992. Data were obtained within one meter of the seabed in depths of 5 m and 10 m. Turbidity was found to vary significantly under natural conditions, with values during storms sometimes exceeding 29 NTU. Tables and plots of turbidity data are presented. (Document contains 77 pages.)

Turbidity threshold sampling for suspended sediment load estimation

Science.gov (United States)

Jack Lewis; Rand Eads

2001-01-01

Abstract - The paper discusses an automated procedure for measuring turbidity and sampling suspended sediment. The basic equipment consists of a programmable data logger, an in situ turbidimeter, a pumping sampler, and a stage-measuring device. The data logger program employs turbidity to govern sample collection during each transport event. Mounting configurations and...

Remote Sensing Marine Ecology: Wind-driven algal blooms in the open oceans and their ecological impacts

Science.gov (United States)

Tang, DanLing

2016-07-01

Algal bloom not only can increase the primary production but also could result in negative ecological consequence, e.g., Harmful Algal Blooms (HABs). According to the classic theory for the formation of algal blooms "critical depth" and "eutrophication", oligotrophic sea area is usually difficult to form a large area of algal blooms, and actually the traditional observation is only sporadic capture to the existence of algal blooms. Taking full advantage of multiple data of satellite remote sensing, this study: 1), introduces "Wind-driven algal blooms in open oceans: observation and mechanisms" It explained except classic coastal Ekman transport, the wind through a variety of mechanisms affecting the formation of algal blooms. Proposed a conceptual model of "Strong wind -upwelling-nutrient-phytoplankton blooms" in Western South China Sea (SCS) to assess role of wind-induced advection transport in phytoplankton bloom formation. It illustrates the nutrient resources that support long-term offshore phytoplankton blooms in the western SCS; 2), Proposal of the theory that "typhoons cause vertical mixing, induce phytoplankton blooms", and quantify their important contribution to marine primary production; Proposal a new ecological index for typhoon. Proposed remote sensing inversion models. 3), Finding of the spatial and temporaldistributions pattern of harmful algal bloom (HAB)and species variations of HAB in the South Yellow Sea and East China Sea, and in the Pearl River estuary, and their oceanic dynamic mechanisms related with monsoon; The project developed new techniques and generated new knowledge, which significantly improved understanding of the formation mechanisms of algal blooms. 1), It proposed "wind-pump" mechanism integrates theoretical system combing "ocean dynamics, development of algal blooms, and impact on primary production", which will benefit fisheries management. 2), A new interdisciplinary subject "Remote Sensing Marine Ecology"(RSME) has been

Use of Moringa oleifera seeds for the removal of turbidity of water supply

Directory of Open Access Journals (Sweden)

Gustavo Lopes Muniz

2015-04-01

Full Text Available Water used for human consumption may contain various impurities and solid particles in suspension that increase its turbidity level. Moringa oleifera Lam is a plant that has the potential to be used as coagulating agent in removing turbidity. The objective of this work was to evaluate the efficiency of Moringa oleifera seeds used in shells and without shells in the removal of turbidity from waters with different degrees of turbidity. Waters were used with 70, 250 and 400 initial NTU obtained synthetically. The extract of moringa seeds was prepared using unshelled and shelled seeds, seeking a simplified procedure and practice. The sedimentation times and dose of coagulant solution used were based on existing recommendations in the literature. All treatments were performed with three replicates and the averages depicted in graphs. The results showed that the use of extract of moringa seeds in shells was more efficient than with unshelled seeds in the removal of turbidity of all treatments and that the shelled seeds removed more than 99% of the initial turbidity of the water samples. Furthermore, there was a direct relationship between turbidity removal efficiency and the level of initial turbidity of the samples. The seeds were more efficient in removing turbidity of the water with a higher level of initial turbidity.

Collagen I self-assembly: revealing the developing structures that generate turbidity.

Science.gov (United States)

Zhu, Jieling; Kaufman, Laura J

2014-04-15

Type I collagen gels are routinely used in biophysical studies and bioengineering applications. The structural and mechanical properties of these fibrillar matrices depend on the conditions under which collagen fibrillogenesis proceeds, and developing a fuller understanding of this process will enhance control over gel properties. Turbidity measurements have long been the method of choice for monitoring developing gels, whereas imaging methods are regularly used to visualize fully developed gels. In this study, turbidity and confocal reflectance microscopy (CRM) were simultaneously employed to track collagen fibrillogenesis and reconcile the information reported by the two techniques, with confocal fluorescence microscopy (CFM) used to supplement information about early events in fibrillogenesis. Time-lapse images of 0.5 mg/ml, 1.0 mg/ml, and 2.0 mg/ml acid-solubilized collagen I gels forming at 27°C, 32°C, and 37°C were collected. It was found that in situ turbidity measured in a scanning transmittance configuration was interchangeable with traditional turbidity measurements using a spectrophotometer. CRM and CFM were employed to reveal the structures responsible for the turbidity that develops during collagen self-assembly. Information from CRM and transmittance images was collapsed into straightforward single variables; total intensity in CRM images tracked turbidity development closely for all collagen gels investigated, and the two techniques were similarly sensitive to fibril number and dimension. Complementary CRM, CFM, and in situ turbidity measurements revealed that fibril and network formation occurred before substantial turbidity was present, and the majority of increasing turbidity during collagen self-assembly was due to increasing fibril thickness. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Increasing precision of turbidity-based suspended sediment concentration and load estimates.

Science.gov (United States)

Jastram, John D; Zipper, Carl E; Zelazny, Lucian W; Hyer, Kenneth E

2010-01-01

Turbidity is an effective tool for estimating and monitoring suspended sediments in aquatic systems. Turbidity can be measured in situ remotely and at fine temporal scales as a surrogate for suspended sediment concentration (SSC), providing opportunity for a more complete record of SSC than is possible with physical sampling approaches. However, there is variability in turbidity-based SSC estimates and in sediment loadings calculated from those estimates. This study investigated the potential to improve turbidity-based SSC, and by extension the resulting sediment loading estimates, by incorporating hydrologic variables that can be monitored remotely and continuously (typically 15-min intervals) into the SSC estimation procedure. On the Roanoke River in southwestern Virginia, hydrologic stage, turbidity, and other water-quality parameters were monitored with in situ instrumentation; suspended sediments were sampled manually during elevated turbidity events; samples were analyzed for SSC and physical properties including particle-size distribution and organic C content; and rainfall was quantified by geologic source area. The study identified physical properties of the suspended-sediment samples that contribute to SSC estimation variance and hydrologic variables that explained variability of those physical properties. Results indicated that the inclusion of any of the measured physical properties in turbidity-based SSC estimation models reduces unexplained variance. Further, the use of hydrologic variables to represent these physical properties, along with turbidity, resulted in a model, relying solely on data collected remotely and continuously, that estimated SSC with less variance than a conventional turbidity-based univariate model, allowing a more precise estimate of sediment loading, Modeling results are consistent with known mechanisms governing sediment transport in hydrologic systems.

Multivariate analysis of the influences of oceanic and meteorological processes on suspended particulate matter distributions in Mississippi coastal waters

Science.gov (United States)

O'Brien, S. J.; Fitzpatrick, P. J.; Dzwonkowski, B.; Dykstra, S. L.; Wallace, D. J.; Church, I.; Wiggert, J. D.

2016-02-01

The Mississippi Sound is influenced by a high volume of sediment discharge from the Biloxi River, Mobile Bay via Pas aux Herons, Pascagoula River, Pearl River, Wolf River, and Lake Pontchartrain through the Rigolets. The river discharge, variable wind speed, wind direction and tides have a significant impact on the turbidity and transport of sediments in the Sound. Level 1 Moderate Resolution Imaging Spectroradiometer (MODIS) data is processed to extract the remote sensing reflectance at the wavelength of 645 nm and binned into an 8-day composite at a resolution of 500 m. The study uses a regional ocean color algorithm to compute suspended particulate matter (SPM) concentration based on these 8-day composite images. Multivariate analysis is applied between the SPM and time series of tides, wind, turbidity and river discharge measured at federal and academic institutions' stations and moorings. The multivariate analysis also includes in situ measurements of suspended sediment concentration and advective exchanges through the Mississippi Sound's tidal inlets between the coastal shelf and the nearshore estuarine waters. Mechanisms underlying the observed spatiotemporal distribution of SPM, including material exchange between the Sound and adjacent shelf waters, will be explored. The results of this study will contribute to current understanding of exchange mechanisms and pathways with the Mississippi Bight via the Mississippi Sound's tidal inlets.

Turbidity Current Head Mixing

Science.gov (United States)

Hernandez, David; Sanchez, Miguel Angel; Medina, Pablo

2010-05-01

A laboratory experimental set - up for studying the behaviour of sediment in presence of a turbulent field with zero mean flow is compared with the behaviour of turbidity currents [1] . Particular interest is shown on the initiation of sediment motion and in the sediment lift - off. The behaviour of the turbidity current in a flat ground is compared with the zero mean flow oscilating grid generated turbulence as when wave flow lifts off suspended sediments [2,3]. Some examples of the results obtained with this set-up relating the height of the head of the turbidity current to the equilibrium level of stirred lutoclines are shown. A turbulent velocity u' lower than that estimated by the Shield diagram is required to start sediment motion. The minimum u' required to start sediment lift - off, is a function of sediment size, cohesivity and resting time. The lutocline height depends on u', and the vorticity at the lutocline seems constant for a fixed sediment size [1,3]. Combining grid stirring and turbidty current head shapes analyzed by means of advanced image analysis, sediment vertical fluxes and settling speeds can be measured [4,5]. [1] D. Hernandez Turbulent structure of turbidity currents and sediment transport Ms Thesis ETSECCPB, UPC. Barcelona 2009. [2] A. Sánchez-Arcilla; A. Rodríguez; J.C. Santás; J.M. Redondo; V. Gracia; R. K'Osyan; S. Kuznetsov; C. Mösso. Delta'96 Surf-zone and nearshore measurements at the Ebro Delta. A: International Conference on Coastal Research through large Scale Experiments (Coastal Dynamics '97). University of Plymouth, 1997, p. 186-187. [3] P. Medina, M. A. Sánchez and J. M. Redondo. Grid stirred turbulence: applications to the initiation of sediment motion and lift-off studies Physics and Chemistry of the Earth, Part B: Hydrology, Oceans and Atmosphere. 26, Issue 4, 2001, Pages 299-304 [4] M.O. Bezerra, M. Diez, C. Medeiros, A. Rodriguez, E. Bahia., A. Sanchez-Arcilla and J.M. Redondo. Study on the influence of waves on

The potentialities of the wind driven engines with Magnus effect

International Nuclear Information System (INIS)

Bychkov, N.M.; Gorelov, V.P.; Gorelov, S.V.; Kachanov, A.N.

1999-01-01

Possibilities of wind engine realizing of Magnus effect like of untraditional kind energy source is shown in the article. In this engine instead of traditional propellers the rotatable cylinders are installed. According interaction of the cylinders with wind the Magnus force arises. Magnus force exceeds propellers rise force in 5-10 times and maintain very large turning moment of wind wheel and most effective operation of engine, especially at low wind rates. Advantage of the engine consists in that it switch on under wind rate 1 m/c, when for propeller one requires 4-5 m/c

Technical note: False low turbidity readings from optical probes during high suspended-sediment concentrations

Science.gov (United States)

Voichick, Nicholas; Topping, David J.; Griffiths, Ronald E.

2018-03-01

Turbidity, a measure of water clarity, is monitored for a variety of purposes including (1) to help determine whether water is safe to drink, (2) to establish background conditions of lakes and rivers and detect pollution caused by construction projects and stormwater discharge, (3) to study sediment transport in rivers and erosion in catchments, (4) to manage siltation of water reservoirs, and (5) to establish connections with aquatic biological properties, such as primary production and predator-prey interactions. Turbidity is typically measured with an optical probe that detects light scattered from particles in the water. Probes have defined upper limits of the range of turbidity that they can measure. The general assumption is that when turbidity exceeds this upper limit, the values of turbidity will be constant, i.e., the probe is pegged; however, this assumption is not necessarily valid. In rivers with limited variation in the physical properties of the suspended sediment, at lower suspended-sediment concentrations, an increase in suspended-sediment concentration will cause a linear increase in turbidity. When the suspended-sediment concentration in these rivers is high, turbidity levels can exceed the upper measurement limit of an optical probe and record a constant pegged value. However, at extremely high suspended-sediment concentrations, optical turbidity probes do not necessarily stay pegged at a constant value. Data from the Colorado River in Grand Canyon, Arizona, USA, and a laboratory experiment both demonstrate that when turbidity exceeds instrument-pegged conditions, increasing suspended-sediment concentration (and thus increasing turbidity) may cause optical probes to record decreasing false turbidity values that appear to be within the valid measurement range of the probe. Therefore, under high-turbidity conditions, other surrogate measurements of turbidity (e.g., acoustic-attenuation measurements or suspended-sediment samples) are necessary to

Effects of turbidity, sediment, and polyacrylamide on native freshwater mussels

Science.gov (United States)

Buczek, Sean B.; Cope, W. Gregory; McLaughlin, Richard A.; Kwak, Thomas J.

2018-01-01

Turbidity is a ubiquitous pollutant adversely affecting water quality and aquatic life in waterways globally. Anionic polyacrylamide (PAM) is widely used as an effective chemical flocculent to reduce suspended sediment (SS) and turbidity. However, no information exists on the toxicity of PAM‐flocculated sediments to imperiled, but ecologically important, freshwater mussels (Unionidae). Thus, we conducted acute (96 h) and chronic (24 day) laboratory tests with juvenile fatmucket (Lampsilis siliquoidea) and three exposure conditions (nonflocculated settled sediment, SS, and PAM‐flocculated settled sediment) over a range of turbidity levels (50, 250, 1,250, and 3,500 nephelometric turbidity units). Survival and sublethal endpoints of protein oxidation, adenosine triphosphate (ATP) production, and protein concentration were used as measures of toxicity. We found no effect of turbidity levels or exposure condition on mussel survival in acute or chronic tests. However, we found significant reductions in protein concentration, ATP production, and oxidized proteins in mussels acutely exposed to the SS condition, which required water movement to maintain sediment in suspension, indicating responses that are symptoms of physiological stress. Our results suggest anionic PAM applied to reduce SS may minimize adverse effects of short‐term turbidity exposure on juvenile freshwater mussels without eliciting additional lethal or sublethal toxicity.

Optical imaging of objects in turbid medium with ultrashort pulses

Science.gov (United States)

Wang, Chih-Yu; Sun, Chia-Wei; Yang, Chih Chung; Kiang, Yean-Woei; Lin, Chii-Wann

2000-07-01

Photons are seriously scattered when entering turbid medium; this the images of objects hidden in turbid medium can not be obtained by just collecting the transmitted photons. Early-arriving photons, which are also called ballistic or snake protons, are much less scattered when passing through turbid medium, and contains more image information than the late-arriving ones. Therefore, objects embedded in turbid medium can be imaged by gathering the ballistic and snake photons. In the present research we try to recover images of objects in turbid medium by simultaneously time-gate and polarization-gate to obtain the snake photons. An Argon-pumped Ti-Sapphire laser with 100fs pulses was employed as a light source. A streak camera with a 2ps temporal resolution was used to extract the ballistic and snake photons. Two pieces of lean swine meat, measured 4mmX3mm and 5xxX4mm, respectively, were placed in a 10cmX10cmX3cm acrylic tank, which was full of diluted milk. A pair of polarizer and an analyzer was used to extract the light that keeps polarization unchanged. The combination of time gating and polarization gating resulted in good images of objects hidden in turbid medium.

Observation technology for remote operation in contaminated turbid water

International Nuclear Information System (INIS)

Kishimoto, Manabu; Mitsui, Takashi

2016-01-01

Remote underwater work in contaminated tanks and pools is one of major decontamination and decommissioning works under high-dose radiation environment. Generally in this kind of work, visual information is limited due to turbid water caused by suspended sludge particles in the water and it makes remote underwater work difficult to be performed safely and efficiently. Therefore, some alternative observation methods to optical cameras have been required. In order to satisfy this requirement, the alternative observation technology which can obtain visual information in contaminated turbid water has been developed since 2014. It is a technology using an acoustic imaging system in a designated airtight container. It provides the visual information in real time regardless of turbidity without significant contamination of any parts of the system. This paper will present development details of this innovative observation technology and its effectiveness to various remote works in contaminated turbid water. (author)

Centrifuge experiments for removal of aluminium turbidity from Dhruva heavy water

International Nuclear Information System (INIS)

Shetiya, R.S.; Unny, V.K.P.; Nayak, A.P.

1989-01-01

Aluminium turbidity and associated radioactivity was observed in the moderator cum coolant system of Dhruva during initial power operation. Ion exchange resin beds of the purification system were not able to remove aluminium turbidity and radioactivity of system heavy water. Centrifuge technique was used as a convenient alternative method to remove the turbidity and radioactivity. (author)

Iterative data-driven load control for flexible wind turbine rotors

OpenAIRE

Navalkar, S.T.

2016-01-01

Wind energy has reached a high degree ofmaturity: for wind-rich onshore locations, it is already competitive with conventional energy sources. However, for low-wind, remote and offshore regions, research efforts are still required to enhance its economic viability. While it is possible to reduce the cost of energy by upscaling wind turbines, it is believed that we may be approaching a plateau in turbine size. Beyond this plateau, the material costs associated with the high dynamic turbine loa...

Sliding mode direct power control of RSC for DFIGs driven by variable speed wind turbines

Directory of Open Access Journals (Sweden)

E.G. Shehata

2015-12-01

Full Text Available In spite of its several advantages, a classic direct power control (DPC of doubly fed induction generators (DFIGs driven by variable speed wind turbines has some drawbacks. In this paper, a simple and robust total sliding mode controller (TSMC is designed to improve the classical DPC performance without complicating the overall scheme. The TSMC is designed to regulate the DFIG stator active and reactive powers. Two integral switching functions are selected for describing the switching surfaces of the active and reactive powers. Reaching phase stability problem of the classical sliding mode controller is avoided in the proposed TSMC. Neither current control loops nor accurate values of machine parameters are required in the proposed scheme. In addition, axes transformation of the stator voltage and current are eliminated. The grid side converter is controlled based on DPC principle to regulate both DC-link voltage and total reactive power. The feasibility of the proposed DPC scheme is validated through simulation studies on a 1.5 MW wind power generation system. The performance of the proposed and conventional DPC schemes is compared under different operating conditions.

Radium isotope (223Ra, 224Ra, 226Ra and 228Ra) distribution near Brazil's largest port, Paranaguá Bay, Brazil

International Nuclear Information System (INIS)

Dias, Thais H.; Oliveira, Joselene de; Sanders, Christian J.; Carvalho, Franciane; Sanders, Luciana M.; Machado, Eunice C.; Sá, Fabian

2016-01-01

This work investigates the 223 Ra, 224 Ra, 226 Ra and 228 Ra isotope distribution in river, estuarine waters and sediments of the Paranaguá Estuarine Complex (PEC). The stratification of the Ra isotopes along water columns indicate differing natural sources. In sediments, the radium isotope activities was inversely proportional to the particle size. The highest concentrations of 223 Ra, 224 Ra, 226 Ra and 228 Ra in the water column were found in the bottom more saline waters and towards the inner of the estuary. These relatively high concentrations towards the bottom of the estuary may be attributed to the influence of tidally driven groundwater source and desorption from particles at the maximum turbidity zone. The apparent river water ages from the radium isotope ratios, 223 Ra/ 224 Ra and 223 Ra/ 228 Ra, indicate that the principal rivers that flow into the estuary have residence times from between 6 and 11 days. - Highlights: • Radium isotope concentrations were evaluated along a large estuarine system. • The radioactivity level in river, estuary and sediments was within a normal range. • Spatial distributions of site specific radionuclides have differing activities and sources.

Technical note: False low turbidity readings from optical probes during high suspended-sediment concentrations

Science.gov (United States)

Voichick, Nicholas; Topping, David; Griffiths, Ronald

2018-01-01

Turbidity, a measure of water clarity, is monitored for a variety of purposes including (1) to help determine whether water is safe to drink, (2) to establish background conditions of lakes and rivers and detect pollution caused by construction projects and stormwater discharge, (3) to study sediment transport in rivers and erosion in catchments, (4) to manage siltation of water reservoirs, and (5) to establish connections with aquatic biological properties, such as primary production and predator–prey interactions. Turbidity is typically measured with an optical probe that detects light scattered from particles in the water. Probes have defined upper limits of the range of turbidity that they can measure. The general assumption is that when turbidity exceeds this upper limit, the values of turbidity will be constant, i.e., the probe is pegged; however, this assumption is not necessarily valid. In rivers with limited variation in the physical properties of the suspended sediment, at lower suspended-sediment concentrations, an increase in suspended-sediment concentration will cause a linear increase in turbidity. When the suspended-sediment concentration in these rivers is high, turbidity levels can exceed the upper measurement limit of an optical probe and record a constant pegged value. However, at extremely high suspended-sediment concentrations, optical turbidity probes do not necessarily stay pegged at a constant value. Data from the Colorado River in Grand Canyon, Arizona, USA, and a laboratory experiment both demonstrate that when turbidity exceeds instrument-pegged conditions, increasing suspended-sediment concentration (and thus increasing turbidity) may cause optical probes to record decreasing false turbidity values that appear to be within the valid measurement range of the probe. Therefore, under high-turbidity conditions, other surrogate measurements of turbidity (e.g., acoustic-attenuation measurements or suspended-sediment samples

Metal-enhanced galactic winds. I

International Nuclear Information System (INIS)

Vader, J.P.

1986-01-01

Supernova-driven gas loss during the early evolution of elliptical galaxies is considered as a possible explanation for the correlations among the observed chemical and structural properties of these systems. Mass loss from systems with a chemically homogeneous interstellar medium does not work. It is pointed out that supernova-driven winds are in fact metal-enhanced with respect to the star-forming gas because the metal production of any supernova that drives the wind is directly flushed out of the galaxy. The fraction of the total metal production lost in the wind is thus at least as large as the fraction epsilon(z) of supernovae that power the wind, independent of the total mass loss. As a corollary, the yield of heavy elements that are recycled in the galaxy is reduced by a factor 1 - epsilon(z). Metal-enhanced galactic winds, which can carry away a large fraction of the metal production in spite of a moderate total mass loss, offer a promising explanation for the low metallicities of dwarf elliptical galaxies. 62 references

Iterative data-driven load control for flexible wind turbine rotors

NARCIS (Netherlands)

Navalkar, S.T.

2016-01-01

Wind energy has reached a high degree ofmaturity: for wind-rich onshore locations, it is already competitive with conventional energy sources. However, for low-wind, remote and offshore regions, research efforts are still required to enhance its economic viability. While it is possible to reduce the

An Improved Adaptive-Torque-Gain MPPT Control for Direct-Driven PMSG Wind Turbines Considering Wind Farm Turbulences

Directory of Open Access Journals (Sweden)

Xiaolian Zhang

2016-11-01

Full Text Available Maximum power point tracking (MPPT plays an important role in increasing the efficiency of a wind energy conversion system (WECS. In this paper, three conventional MPPT methods are reviewed: power signal feedback (PSF control, decreased torque gain (DTG control, and adaptive torque gain (ATG control, and their potential challenges are investigated. It is found out that the conventional MPPT method ignores the effect of wind turbine inertia and wind speed fluctuations, which lowers WECS efficiency. Accordingly, an improved adaptive torque gain (IATG method is proposed, which customizes adaptive torque gains and enhances MPPT performances. Specifically, the IATG control considers wind farm turbulences and works out the relationship between the optimal torque gains and the wind speed characteristics, which has not been reported in the literature. The IATG control is promising, especially under the ongoing trend of building wind farms with large-scale wind turbines and at low and medium wind speed sites.

Towards environmental management of water turbidity within open coastal waters of the Great Barrier Reef.

Science.gov (United States)

Macdonald, Rachael K; Ridd, Peter V; Whinney, James C; Larcombe, Piers; Neil, David T

2013-09-15

Water turbidity and suspended sediment concentration (SSC) are commonly used as part of marine monitoring and water quality plans. Current management plans utilise threshold SSC values derived from mean-annual turbidity concentrations. Little published work documents typical ranges of turbidity for reefs within open coastal waters. Here, time-series turbidity measurements from 61 sites in the Great Barrier Reef (GBR) and Moreton Bay, Australia, are presented as turbidity exceedance curves and derivatives. This contributes to the understanding of turbidity and SSC in the context of environmental management in open-coastal reef environments. Exceedance results indicate strong spatial and temporal variability in water turbidity across inter/intraregional scales. The highest turbidity across 61 sites, at 50% exceedance (T50) is 15.3 NTU and at 90% exceedance (T90) 4.1 NTU. Mean/median turbidity comparisons show strong differences between the two, consistent with a strongly skewed turbidity regime. Results may contribute towards promoting refinement of water quality management protocols. Copyright © 2013 Elsevier Ltd. All rights reserved.

Determination of the effect of wind velocity and direction changes on turbidity removal in rectangular sedimentation tanks.

Science.gov (United States)

Khezri, Seyed Mostafa; Biati, Aida; Erfani, Zeynab

2012-01-01

In the present study, a pilot-scale sedimentation tank was used to determine the effect of wind velocity and direction on the removal efficiency of particles. For this purpose, a 1:20 scale pilot simulated according to Frude law. First, the actual efficiency of total suspended solids (TSS) removal was calculated in no wind condition. Then, the wind was blown in the same and the opposite directions of water flow. At each direction TSS removal was calculated at three different velocities from 2.5 to 7 m/s. Results showed that when the wind was in the opposite direction of water flow, TSS removal efficiency initially increased with the increase of wind velocity from 0 to 2.5 m/s, then it decreased with the increase of velocity to 5 m/s. This mainly might happen because the opposite direction of wind can increase particles' retention time in the sedimentation tank. However, higher wind velocities (i.e. 3.5 and 5.5 m/s) could not increase TSS removal efficiency. Thus, if sedimentation tanks are appropriately exposed to the wind, TSS removal efficiency increases by approximately 6%. Therefore, energy consumption will be reduced by a proper site selection for sedimentation tank unit in water and waste water treatment plants.

Post-lens tear turbidity and visual quality after scleral lens wear.

Science.gov (United States)

Carracedo, Gonzalo; Serramito-Blanco, Maria; Martin-Gil, Alba; Wang, Zicheng; Rodriguez-Pomar, Candela; Pintor, Jesús

2017-11-01

The aim was to evaluate the turbidity and thickness of the post-lens tear layer and its effect on visual quality in patients with keratoconus after the beginning of lens wear and before lens removal at the end of eight hours. Twenty-six patients with keratoconus (aged 36.95 ± 8.95 years) participated voluntarily in the study. The sample was divided into two groups: patients with intrastromal corneal ring (ICRS group) and patients without ICRS (KC group). Distance visual acuity (VA), contrast sensitivity, pachymetry, post-lens tear layer height and post-lens tear layer turbidity (percentage area occupied and number of particles per mm 2 ) were evaluated with optical coherence tomography before and after wearing a scleral lens. A significant increase of turbidity was found in all groups assessed (p turbidity parameters with distance VA but no correlation between turbidity and post-lens tear layer thickness at the beginning was found (p > 0.05). A strong correlation in all groups between the post-lens tear layer at the beginning and differences of tear layer thickness between two measures was also found (p turbidity. © 2017 Optometry Australia.

Robust sensor for turbidity measurement from light scattering and absorbing liquids.

Science.gov (United States)

Kontturi, Ville; Turunen, Petri; Uozumi, Jun; Peiponen, Kai-Erik

2009-12-01

Internationally standardized turbidity measurements for probing solid particles in liquid are problematic in the case of simultaneous light scattering and absorption. A method and a sensor to determine the turbidity in the presence of light absorption are presented. The developed sensor makes use of the total internal reflection of a laser beam at the liquid-prism interface, and the turbidity is assessed using the concept of laser speckle pattern. Using average filtering in speckle data analyzing the observed dynamic speckle pattern, which is due to light scattering from particles and the static speckle due to stray light of the sensor, can be separated from each other. Good correlation between the standard deviation of dynamic speckle and turbidity value for nonabsorbing and for absorbing liquids was observed. The sensor is suggested, for instance, for the measurement of ill-behaved as well as small-volume turbid liquids in both medicine and process industry.

Light diffusion in N-layered turbid media: steady-state domain.

Science.gov (United States)

Liemert, André; Kienle, Alwin

2010-01-01

We deal with light diffusion in N-layered turbid media. The steady-state diffusion equation is solved for N-layered turbid media having a finite or an infinitely thick N'th layer. Different refractive indices are considered in the layers. The Fourier transform formalism is applied to derive analytical solutions of the fluence rate in Fourier space. The inverse Fourier transform is calculated using four different methods to test their performance and accuracy. Further, to avoid numerical errors, approximate formulas in Fourier space are derived. Fast solutions for calculation of the spatially resolved reflectance and transmittance from the N-layered turbid media ( approximately 10 ms) with small relative differences (<10(-7)) are found. Additionally, the solutions of the diffusion equation are compared to Monte Carlo simulations for turbid media having up to 20 layers.

Aluminum Corrosion and Turbidity

International Nuclear Information System (INIS)

Longtin, F.B.

2003-01-01

Aluminum corrosion and turbidity formation in reactors correlate with fuel sheath temperature. To further substantiate this correlation, discharged fuel elements from R-3, P-2 and K-2 cycles were examined for extent of corrosion and evidence of breaking off of the oxide film. This report discusses this study

Radiation Belt Transport Driven by Solar Wind Dynamic Pressure Fluctuations

Science.gov (United States)

Kress, B. T.; Hudson, M. K.; Ukhorskiy, A. Y.; Mueller, H.

2012-12-01

The creation of the Earth's outer zone radiation belts is attributed to earthward transport and adiabatic acceleration of electrons by drift-resonant interactions with electromagnetic fluctuations in the magnetosphere. Three types of radial transport driven by solar wind dynamic pressure fluctuations that have been identified are: (1) radial diffusion [Falthammer, 1965], (2) significant changes in the phase space density radial profile due to a single or few ULF drift-resonant interactions [Ukhorskiy et al., 2006; Degeling et al., 2008], and (3) shock associated injections of radiation belt electrons occurring in less than a drift period [Li et al., 1993]. A progress report will be given on work to fully characterize different forms of radial transport and their effect on the Earth's radiation belts. The work is being carried out by computing test-particle trajectories in electric and magnetic fields from a simple analytic ULF field model and from global MHD simulations of the magnetosphere. Degeling, A. W., L. G. Ozeke, R. Rankin, I. R. Mann, and K. Kabin (2008), Drift resonant generation of peaked relativistic electron distributions by Pc 5 ULF waves, textit{J. Geophys. Res., 113}, A02208, doi:10.1029/2007JA012411. Fälthammar, C.-G. (1965), Effects of Time-Dependent Electric Fields on Geomagnetically Trapped Radiation, J. Geophys. Res., 70(11), 2503-2516, doi:10.1029/JZ070i011p02503. Li, X., I. Roth, M. Temerin, J. R. Wygant, M. K. Hudson, and J. B. Blake (1993), Simulation of the prompt energization and transport of radiation belt particles during the March 24, 1991 SSC, textit{Geophys. Res. Lett., 20}(22), 2423-2426, doi:10.1029/93GL02701. Ukhorskiy, A. Y., B. J. Anderson, K. Takahashi, and N. A. Tsyganenko (2006), Impact of ULF oscillations in solar wind dynamic pressure on the outer radiation belt electrons, textit{Geophys. Res. Lett., 33}(6), L06111, doi:10.1029/2005GL024380.

Electrochemical filtration for turbidity removal in industrial cooling/process water systems

International Nuclear Information System (INIS)

Kumbhar, A.G.; Venkateswaran, G.

2008-01-01

Water samples of large cooling water reservoirs may look visibly clear and transparent, but still may contain sub-micron size particles at sub-parts-per-million levels. Deposition of these particles on heat exchanger surfaces, reduces the heat transfer efficiency in power industry. In nuclear power plants, additionally it creates radiation exposure problems due to activation of fine metallic turbidity in the reactor core and its subsequent transfer to out-of-core surfaces. Sub-micron filtration creates back high-pressure problem. Zeta filters available commercially are prescribed for separating either positively or negatively charged particles. They are of once-use and throw-type. Precipitation surface modified ion exchangers impart chemical impurities to the system. Thus, sub-micron size and dilute turbidity removal from large volumes of waters such as heat exchanger cooling water in nuclear and power industry poses a problem. Electro deposition of the turbidity causing particles, on porous carbon/graphite felt electrodes, is one of the best suited methods for turbidity removal from large volumes of water due to the filter's high permeability, inertness to the system and regenerability resulting in low waste generation. Initially, active indium turbidity removal from RAPS-1 heavy water moderator system, and microbes removal from heat exchanger cooling lake water of RAPS 1 and 2 were demonstrated with in-house designed and fabricated prototype electrochemical filter (ECF). Subsequently, a larger size, high flow filter was fabricated and deployed for iron turbidity removal from active process waters system of Kaiga Generation Station unit 1 and silica and iron turbidity removal from cooling water pond used for heat exchanger of a high temperature high pressure (HTHP) loop at WSCD, Kalpakkam. The ECF proved its exclusive utility for sub-micron size turbidity removal and microbes removal. ECF maneuverability with potential and current for both positively and

Sediment-induced turbidity impairs foraging performance and prey choice of planktivorous coral reef fishes.

Science.gov (United States)

Johansen, J L; Jones, G P

2013-09-01

Sedimentation is a substantial threat to aquatic ecosystems and a primary cause of habitat degradation on near-shore coral reefs. Although numerous studies have demonstrated major impacts of sedimentation and turbidity on corals, virtually nothing is known of the sensitivity of reef fishes. Planktivorous fishes are an important trophic group that funnels pelagic energy sources into reef ecosystems. These fishes are visual predators whose foraging is likely to be impaired by turbidity, but the threshold for such effects and their magnitude are unknown. This study examined the effect of sediment-induced turbidity on foraging in four species of planktivorous damselfishes (Pomacentridae) of the Great Barrier Reef, including inshore and offshore species that potentially differ in tolerance for turbidity. An experimental flow tunnel was used to quantify their ability to catch mobile and immobile planktonic prey under different levels of turbidity and velocity in the range encountered on natural and disturbed reefs. Turbidity of just 4 NTU (nephelometric turbidity units) reduced average attack success by up to 56%, with higher effect sizes for species with offshore distributions. Only the inshore species (Neopomacentrus bankieri), which frequently encounters this turbidity on coastal reefs, could maintain high prey capture success. At elevated turbidity similar to that found on disturbed reefs (8 NTU), attack success was reduced in all species examined by up to 69%. These reductions in attack success led to a 21-24% decrease in foraging rates for all mid to outer-shelf species, in spite of increasing attack rates at high turbidity. Although effects of turbidity varied among species, it always depended heavily on prey mobility and ambient velocity. Attack success was up to 14 times lower on mobile prey, leaving species relatively incapable of foraging on anything but immobile prey at high turbidity. Effects of turbidity were particularly prominent at higher velocities, as

Thermal loading of wind power converter considering dynamics of wind speed

DEFF Research Database (Denmark)

Baygildina, Elvira; Peltoniemi, Pasi; Pyrhönen, Olli

2013-01-01

The thermal loading of power semiconductors is a crucial performance related to the reliability and cost of the wind power converter. However, the thermal loading impacts by the variation of wind speeds have not yet been clarified, especially when considering the aerodynamic behavior of the wind...... turbines. In this paper, the junction temperatures in the wind power converter are studied under not only steady state, but also turbulent wind speed conditions. The study is based on a 1.5 MW direct-driven turbine system with aerodynamic model described by Unsteady Blade Element Momentum Method (BEMM......), and the thermal stress of power devices is investigated from the frequency spectrum point of view of wind speed. It is concluded that because of the strong inertia effects by the aerodynamic behavior of wind turbines, thermal stress of the semiconductors is relatively more stable and only influenced by the low...

Investigating Rhône River plume (Gulf of Lions, France) dynamics using metrics analysis from the MERIS 300m Ocean Color archive (2002-2012)

Science.gov (United States)

Gangloff, Aurélien; Verney, Romaric; Doxaran, David; Ody, Anouck; Estournel, Claude

2017-07-01

In coastal environments, river plumes are major transport mechanisms for particulate matter, nutriments and pollutants. Ocean color satellite imagery is a valuable tool to explore river turbid plume characteristics, providing observations at high temporal and spatial resolutions of suspended particulate matter (SPM) concentration over a long time period, covering a wide range of hydro-meteorological conditions. We propose here to use the MERIS-FR (300m) Ocean Color archive (2002-2012) in order to investigate Rhône River turbid plume patterns generated by the two main forcings acting on the north-eastern part of the Gulf of Lions (France): wind and river freshwater discharge. Results are exposed considering plume metrics (area of extension, south-east-westernmost points, shape, centroid, SPM concentrations) extracted from satellite data using an automated image-processing tool. Rhône River turbid plume SPM concentrations and area of extension are shown to be mainly driven by the river outflow while wind direction acts on its shape and orientation. This paper also presents the region of influence of the Rhône River turbid plume over monthly and annual periods, and highlights its interannual variability.

Preliminary Dynamic Feasibility and Analysis of a Spherical, Wind-Driven (Tumbleweed), Martian Rover

Science.gov (United States)

Flick, John J.; Toniolo, Matthew D.

2005-01-01

The process and findings are presented from a preliminary feasibility study examining the dynamics characteristics of a spherical wind-driven (or Tumbleweed) rover, which is intended for exploration of the Martian surface. The results of an initial feasibility study involving several worst-case mobility situations that a Tumbleweed rover might encounter on the surface of Mars are discussed. Additional topics include the evaluation of several commercially available analysis software packages that were examined as possible platforms for the development of a Monte Carlo Tumbleweed mission simulation tool. This evaluation lead to the development of the Mars Tumbleweed Monte Carlo Simulator (or Tumbleweed Simulator) using the Vortex physics software package from CM-Labs, Inc. Discussions regarding the development and evaluation of the Tumbleweed Simulator, as well as the results of a preliminary analysis using the tool are also presented. Finally, a brief conclusions section is presented.

Predicting Migratory Corridors of White Storks, Ciconia ciconia, to Enhance Sustainable Wind Energy Planning: A Data-Driven Agent-Based Model

Directory of Open Access Journals (Sweden)

Francis Oloo

2018-05-01

Full Text Available White storks (Ciconia ciconia are birds that make annual long-distance migration flights from their breeding grounds in the Northern Hemisphere to the south of Africa. These trips take place in the winter season, when the temperatures in the North fall and food supply drops. White storks, because of their large size, depend on the wind, thermals, and orographic characteristics of the environment in order to minimize their energy expenditure during flight. In particular, the birds adopt a soaring behavior in landscapes where the thermal uplift and orographic updrafts are conducive. By attaining suitable soaring heights, the birds then use the wind characteristics to glide for hundreds of kilometers. It is therefore expected that white storks would prefer landscapes that are characterized by suitable wind and thermal characteristics, which promote the soaring and gliding behaviors. However, these same landscapes are also potential sites for large-scale wind energy generation. In this study, we used the observed data of the white stork movement trajectories to specify a data-driven agent-based model, which simulates flight behavior of the white storks in a dynamic environment. The data on the wind characteristics and thermal uplift are dynamically changed on a daily basis so as to mimic the scenarios that the observed birds experienced during flight. The flight corridors that emerge from the simulated flights are then combined with the predicted surface on the wind energy potential, in order to highlight the potential risk of collision between the migratory white storks and hypothetical wind farms in the locations that are suitable for wind energy developments. This work provides methods that can be adopted to assess the overlap between wind energy potential and migratory corridors of the migration of birds. This can contribute to achieving sustainable trade-offs between wind energy development and conservation of wildlife and, hence, handling the

A drifter for measuring water turbidity in rivers and coastal oceans.

Science.gov (United States)

Marchant, Ross; Reading, Dean; Ridd, James; Campbell, Sean; Ridd, Peter

2015-02-15

A disposable instrument for measuring water turbidity in rivers and coastal oceans is described. It transmits turbidity measurements and position data via a satellite uplink to a processing server. The primary purpose of the instrument is to help document changes in sediment runoff from river catchments in North Queensland, Australia. The 'river drifter' is released into a flooded river and drifts downstream to the ocean, measuring turbidity at regular intervals. Deployment in the Herbert River showed a downstream increase in turbidity, and thus suspended sediment concentration, while for the Johnstone River there was a rapid reduction in turbidity where the river entered the sea. Potential stranding along river banks is a limitation of the instrument. However, it has proved possible for drifters to routinely collect data along 80 km of the Herbert River. One drifter deployed in the Fly River, Papua New Guinea, travelled almost 200 km before stranding. Copyright © 2014 Elsevier Ltd. All rights reserved.

Interrelation of surface tension, optical turbidity, and color of operational transformer oils

International Nuclear Information System (INIS)

L’vov, S. Yu.; Lyut’ko, E. O.; Lankau, Ya. V.; Komarov, V. B.; Seliverstov, A. F.; Bondareva, V. N.; L’vov, Yu. N.; L’vov, M. Yu.; Ershov, B. G.

2011-01-01

Measurements of the acidity, optical turbidity, surface tension, and color of transformer oil from 54 power transformers, autotransformers, and shunt reactors are reported. Changes in surface tension, optical turbidity, and color are found to obey adequate linear correlations, while the acidity has no correlation with any of these properties. Numerical criteria for the maximum permissible state (quality) of the oil with respect to optical turbidity and color are obtained. Recommendations to operating staff are provided for cases in which the criteria for optical turbidity and color are exceeded.

2016 Wind Technologies Market Report

Energy Technology Data Exchange (ETDEWEB)

Wiser, Ryan [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Bolinger, Mark [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

2017-08-08

Wind power capacity in the United States experienced strong growth in 2016. Recent and projected near-term growth is supported by the industry’s primary federal incentive—the production tax credit (PTC)—as well as a myriad of state-level policies. Wind additions have also been driven by improvements in the cost and performance of wind power technologies, yielding low power sales prices for utility, corporate, and other purchasers.

Delft Dashboard: a quick setup tool for coastal and estuarine models

Science.gov (United States)

Nederhoff, C., III; Van Dongeren, A.; Van Ormondt, M.; Veeramony, J.

2016-02-01

We developed easy-to-use Delft DashBoard (DDB) software for the rapid set-up of coastal and estuarine hydrodynamic and basic morphological numerical models. In the "Model Maker" toolbox, users have the capability to set-up Delft3D models, in a minimal amount of time (in the order of a hour), for any location in the world. DDB draws upon public internet data sources of bathymetry and tidesto construct the model. With additional toolboxes, these models can be forced with parameterized hurricane wind fields, uplift of the sea surface due to tsunamis nested in publically available ocean models and forced with meteo data (wind speed, pressure, temperature) In this presentation we will show the skill of a model which is setup with Delft Dashboard and compare it to well-calibrated benchmark models. These latter models have been set-up using detailed input data and boundary conditions. We have tested the functionality of Delft DashBoard and evaluate the performance and robustness of the DDB model system on a variety of cases, ranging from a coastal to basin models. Furthermore, we have performed a sensitivity study to investigate the most critical physical and numerical processes. The software can benefit operational modellers, as well as scientists and consultants.

Meta-analysis of estuarine nurseries

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Densities of juvenile fishery species and other animals (all generally 100 mm total length) were summarized for shallow estuarine areas along coastal Texas and...

Environmental conditions and intraspecific interference: unexpected effects of turbidity on pike (Esox lucius) foraging

DEFF Research Database (Denmark)

Nilsson, P.A.; Jacobsen, Lene; Berg, Søren

2009-01-01

on pike foraging alone or among conspecifics in different levels of water turbidity, we expected high turbidity to decrease the perceived risk of intraspecific interactions among pike, and thereby decrease the strength of interference, as turbidity would decrease the visual contact between individuals...... and act as a refuge from behavioural interactions. The results show that this is not the case, but suggest that interference is induced instead of reduced in high turbidity. Per capita foraging rates do not differ between pike foraging alone or in groups in our clear and moderately turbid treatments......, indicating no effect of interference. As high turbidity enhances prey consumption for pike individuals foraging alone, but does not have this effect for pike in groups, high turbidity induces the relative interference effect. We suggest that future evaluations of the stabilizing effects of interference...

System Efficiency of a Tap Transformer Based Grid Connection Topology Applied on a Direct Driven Generator for Wind Power

Directory of Open Access Journals (Sweden)

Senad Apelfröjd

2014-01-01

Full Text Available Results from experiments on a tap transformer based grid connection system for a variable speed vertical axis wind turbine are presented. The tap transformer based system topology consists of a passive diode rectifier, DC-link, IGBT inverter, LCL-filter, and tap transformer. Full range variable speed operation is enabled by using the different step-up ratios of a tap transformer. Simulations using MATLAB/Simulink have been performed in order to study the behavior of the system. A full experimental set up of the system has been used in the laboratory study, where a clone of the on-site generator was driven by an induction motor and the system was connected to a resistive load to better evaluate the performance. Furthermore, the system is run and evaluated for realistic wind speeds and variable speed operation. For a more complete picture of the system performance, a case study using real site Weibull parameters is done, comparing different tap selection options. The results show high system efficiency at nominal power and an increase in overall power output for full tap operation in comparison with the base case, a standard transformer. In addition, the loss distribution at different wind speeds is shown, which highlights the dominant losses at low and high wind speeds. Finally, means for further increasing the overall system efficiency are proposed.

System efficiency of a tap transformer based grid connection topology applied on a direct driven generator for wind power.

Science.gov (United States)

Apelfröjd, Senad; Eriksson, Sandra

2014-01-01

Results from experiments on a tap transformer based grid connection system for a variable speed vertical axis wind turbine are presented. The tap transformer based system topology consists of a passive diode rectifier, DC-link, IGBT inverter, LCL-filter, and tap transformer. Full range variable speed operation is enabled by using the different step-up ratios of a tap transformer. Simulations using MATLAB/Simulink have been performed in order to study the behavior of the system. A full experimental set up of the system has been used in the laboratory study, where a clone of the on-site generator was driven by an induction motor and the system was connected to a resistive load to better evaluate the performance. Furthermore, the system is run and evaluated for realistic wind speeds and variable speed operation. For a more complete picture of the system performance, a case study using real site Weibull parameters is done, comparing different tap selection options. The results show high system efficiency at nominal power and an increase in overall power output for full tap operation in comparison with the base case, a standard transformer. In addition, the loss distribution at different wind speeds is shown, which highlights the dominant losses at low and high wind speeds. Finally, means for further increasing the overall system efficiency are proposed.

System Efficiency of a Tap Transformer Based Grid Connection Topology Applied on a Direct Driven Generator for Wind Power

Science.gov (United States)

2014-01-01

Results from experiments on a tap transformer based grid connection system for a variable speed vertical axis wind turbine are presented. The tap transformer based system topology consists of a passive diode rectifier, DC-link, IGBT inverter, LCL-filter, and tap transformer. Full range variable speed operation is enabled by using the different step-up ratios of a tap transformer. Simulations using MATLAB/Simulink have been performed in order to study the behavior of the system. A full experimental set up of the system has been used in the laboratory study, where a clone of the on-site generator was driven by an induction motor and the system was connected to a resistive load to better evaluate the performance. Furthermore, the system is run and evaluated for realistic wind speeds and variable speed operation. For a more complete picture of the system performance, a case study using real site Weibull parameters is done, comparing different tap selection options. The results show high system efficiency at nominal power and an increase in overall power output for full tap operation in comparison with the base case, a standard transformer. In addition, the loss distribution at different wind speeds is shown, which highlights the dominant losses at low and high wind speeds. Finally, means for further increasing the overall system efficiency are proposed. PMID:25258733

Marine and Estuarine Pollution.

Science.gov (United States)

Reish, Donald J.

1978-01-01

Presents a literature review of the effects of various pollutants on marine and estuarine organisms, covering publications of 1976-77. This review includes: (1) effects of pesticides, dredging, dumping, sludge, and petroleum hydrocarbons; and (2) diseases and tissue abnormalities. A list of 441 references is also presented. (HM)

Turbidity affects foraging success of drift-feeding rosyide dace

Science.gov (United States)

Richard M. Zamor; Gary D. Grossman

2007-01-01

The effects of suspended sediment on nongame fishes are not well understood. We examined the effects of suspended sediment (i.e., turbidity) on reactive distance and prey capture success at springautumn (12°C) and summer (18°C) temperatures for royside dace Clinostomus funduloides in an artificial stream. Experimental turbidities ranged from 0 to 56...

Generalized weighted ratio method for accurate turbidity measurement over a wide range.

Science.gov (United States)

Liu, Hongbo; Yang, Ping; Song, Hong; Guo, Yilu; Zhan, Shuyue; Huang, Hui; Wang, Hangzhou; Tao, Bangyi; Mu, Quanquan; Xu, Jing; Li, Dejun; Chen, Ying

2015-12-14

Turbidity measurement is important for water quality assessment, food safety, medicine, ocean monitoring, etc. In this paper, a method that accurately estimates the turbidity over a wide range is proposed, where the turbidity of the sample is represented as a weighted ratio of the scattered light intensities at a series of angles. An improvement in the accuracy is achieved by expanding the structure of the ratio function, thus adding more flexibility to the turbidity-intensity fitting. Experiments have been carried out with an 850 nm laser and a power meter fixed on a turntable to measure the light intensity at different angles. The results show that the relative estimation error of the proposed method is 0.58% on average for a four-angle intensity combination for all test samples with a turbidity ranging from 160 NTU to 4000 NTU.

Wind resource characterization in the Arabian Peninsula

KAUST Repository

Yip, Chak Man Andrew; Gunturu, Udaya; Stenchikov, Georgiy L.

2015-01-01

Wind energy is expected to contribute to alleviating the rise in energy demand in the Middle East that is driven by population growth and industrial development. However, variability and intermittency in the wind resource present significant

Assessment of the suitability of Durafet-based sensors for pH measurement in dynamic estuarine environments

Science.gov (United States)

Gonski, Stephen F.; Cai, Wei-Jun; Ullman, William J.; Joesoef, Andrew; Main, Christopher R.; Pettay, D. Tye; Martz, Todd R.

2018-01-01

The suitability of the Honeywell Durafet to the measurement of pH in productive, high-fouling, and highly-turbid estuarine environments was investigated at the confluence of the Murderkill Estuary and Delaware Bay (Delaware, USA). Three different flow configurations of the SeapHOx sensor equipped with a Honeywell Durafet and its integrated internal (Ag/AgCl reference electrode containing a 4.5 M KCl gel liquid junction) and external (solid-state chloride ion selective electrode, Cl-ISE) reference electrodes were deployed for four periods between April 2015 and September 2016. In this environment, the Honeywell Durafet proved capable of making high-resolution and high-frequency pH measurements on the total scale between pH 6.8 and 8.4. Natural pH fluctuations of >1 pH unit were routinely captured over a range of timescales. The sensor pH collected between May and August 2016 using the most refined SeapHOx configuration exhibited good agreement with multiple sets of independently measured reference pH values. When deployed in conjunction with rigorous discrete sampling and calibration schemes, the sensor pH had a root-mean squared error ranging between 0.011 and 0.036 pH units across a wide range of salinity relative to both pHT calculated from measured dissolved inorganic carbon and total alkalinity and pHNBS measured with a glass electrode corrected to pHT at in situ conditions. The present work demonstrates the viability of the Honeywell Durafet to the measurement of pH to within the weather-level precision defined by the Global Ocean Acidification Observing Network (GOA-ON, ≤ 0.02 pH units) as a part of future estuarine CO2 chemistry studies undertaken in dynamic environments.

Newly recognized turbidity current structure can explain prolonged flushing of submarine canyons.

Science.gov (United States)

Azpiroz-Zabala, Maria; Cartigny, Matthieu J B; Talling, Peter J; Parsons, Daniel R; Sumner, Esther J; Clare, Michael A; Simmons, Stephen M; Cooper, Cortis; Pope, Ed L

2017-10-01

Seabed-hugging flows called turbidity currents are the volumetrically most important process transporting sediment across our planet and form its largest sediment accumulations. We seek to understand the internal structure and behavior of turbidity currents by reanalyzing the most detailed direct measurements yet of velocities and densities within oceanic turbidity currents, obtained from weeklong flows in the Congo Canyon. We provide a new model for turbidity current structure that can explain why these are far more prolonged than all previously monitored oceanic turbidity currents, which lasted for only hours or minutes at other locations. The observed Congo Canyon flows consist of a short-lived zone of fast and dense fluid at their front, which outruns the slower moving body of the flow. We propose that the sustained duration of these turbidity currents results from flow stretching and that this stretching is characteristic of mud-rich turbidity current systems. The lack of stretching in previously monitored flows is attributed to coarser sediment that settles out from the body more rapidly. These prolonged seafloor flows rival the discharge of the Congo River and carry ~2% of the terrestrial organic carbon buried globally in the oceans each year through a single submarine canyon. Thus, this new structure explains sustained flushing of globally important amounts of sediment, organic carbon, nutrients, and fresh water into the deep ocean.

Single-sided natural ventilation driven by wind pressure and temperature difference

DEFF Research Database (Denmark)

Larsen, Tine Steen; Heiselberg, Per

2008-01-01

-scale wind tunnel experiments have been made with the aim of making a new expression for calculation of the airflow rate in single-sided natural ventilation. During the wind tunnel experiments it was found that the dominating driving force differs between wind speed and temperature difference depending......Even though opening a window for ventilation of a room seems very simple, the flow that occurs in this situation is rather complicated. The amount of air going through the window opening will depend on the wind speed near the building, the temperatures inside and outside the room, the wind...

Design Optimization and Evaluation of Different Wind Generator Systems

DEFF Research Database (Denmark)

Chen, Zhe; Li, Hui

2008-01-01

. In this paper, seven variable speed constant frequency (VSCF) wind generator systems are investigated, namely permanent magnet synchronous generators with the direct-driven (PMSG_DD), the single-stage gearbox (PMSG_1G) and three-stage gearbox (PMSG_3G) concepts, doubly fed induction generators with the three......With rapid development of wind power technologies and significant growth of wind power capacity installed worldwide, various wind generator systems have been developed and built. The objective of this paper is to evaluate various wind generator systems by optimization designs and comparisons......-stage gearbox (DFIG_3G) and with the single-stage gearbox (DFIG_1G), the electricity excited synchronous generator with the direct-driven (EESG_DD), and the VSCF squirrel cage induction generator with the three-stage gearbox (SCIG_3G). Firstly, the design models of wind turbines, three/single stage gearbox...

40 CFR 141.560 - Is my system subject to individual filter turbidity requirements?

Science.gov (United States)

2010-07-01

... filter turbidity requirements? 141.560 Section 141.560 Protection of Environment ENVIRONMENTAL PROTECTION... Filtration and Disinfection-Systems Serving Fewer Than 10,000 People Individual Filter Turbidity Requirements § 141.560 Is my system subject to individual filter turbidity requirements? If your system is a subpart...

[Exploration of the Essence of "Endogenous Turbidity" in Chinese Medicine].

Science.gov (United States)

Fan, Xin-rong; Tang, Nong; Ji, Yun-xi; Zhang, Yao-zhong; Jiang, Li; Huang, Gui-hua; Xie, Sheng; Li, Liu-mei; Song, Chun-hui; Ling, Jiang-hong

2015-08-01

The essence of endogenous turbidity in Chinese medicine (CM) is different from cream, fat, phlegm, retention, damp, toxicity, and stasis. Along with the development of modern scientific technologies and biology, researches on the essence of endogenous turbidity should keep pace with the time. Its material bases should be defined and new connotation endowed at the microscopic level. The essence of turbidity lies in abnormal functions of zang-fu organs. Sugar, fat, protein, and other nutrient substances cannot be properly decomposed, but into semi-finished products or intermediate metabolites. They are inactive and cannot participate in normal material syntheses and decomposition. They cannot be transformed to energy metabolism, but also cannot be synthesized as executive functioning of active proteins. If they cannot be degraded by autophagy-lysosome or ubiquitin-prosome into glucose, fatty acids, amino acids, and other basic nutrients to be used again, they will accumulate inside the human body and become endogenous turbidity. Therefore, endogenous turbidity is different from final metabolites such as urea, carbon dioxide, etc., which can transform vital qi. How to improve the function of zang-fu organs, enhance its degradation by autophagy-lysosome or ubiquitin-prosome is of great significance in normal operating of zang-fu organs and preventing the emergence and progress of related diseases.

Treatment of water turbidity and bacteria by using a coagulant extracted from Plantago ovata

Directory of Open Access Journals (Sweden)

Bahman Ramavandi

2014-08-01

Full Text Available A biocoagulant was successfully extracted from Plantago ovata by using an FeCl3-induced crude extract (FCE. The potential of FCE to act as a natural coagulant was tested for clarification using the turbid water of a river. Experimental tests were performed to evaluate the effects of turbidity concentration, coagulant quantity, water pH, and humic acid concentration on the coagulation of water turbidity by FCE. The maximum turbidity removal was occurred at water pH<8. At the optimum dosage of FCE, only 0.8 mg/L of dissolved organic carbon was released to the treated water. An increase in the humic acid led to the promotion of the water turbidity removal. Results demonstrated that the FCE removed more than 95.6% of all initial turbidity concentrations (50–300 NTU. High bacteriological quality was achieved in the treated water. FCE as an eco-friendly biocoagulant was revealed to be a very efficient coagulant for removing turbidity from waters.

How functional traits of estuarine macrobenthic assemblages respond to metal contamination?

KAUST Repository

Piló, D.

2016-08-06

surface deposit-feeder species. The most representative species associated with this area was the gastropod Peringia ulvae. Less contaminated sites revealed large-sized specimens, carnivores and swimmers, mainly represented by the polychaete Nephtys hombergii. This finding is consistent with other studies addressing different kinds of disturbance, where a shift in dominance from carnivore/predators, long-lived and large animals to the predominance of small-size, short-lived and deposit-feeders has been observed across increasing gradients of disturbance. Our results reinforce the importance of macrobenthic functional traits analysis to assess human disturbances driven impacts in multi-stressed estuarine ecosystems. By analysing the environmental variables with different origins independently, we were able to draw conclusions about the effects of human pressures (metals) on macrobenthic traits. Such distinction can be particularly useful to isolate different environmental descriptors and assess their effects on functional diversity, making the current approach promising in evaluation the ecological effects of anthropogenic stressors in estuarine areas. © 2016 Elsevier Ltd

Comparison of Water Turbidity Removal Efficiencies of Descurainia Sophia Seed Extract and Ferric chloride

Directory of Open Access Journals (Sweden)

Mazyar Peyda

2016-03-01

Full Text Available Background Turbidity removal using inorganic coagulants such as iron and aluminum salts in water treatment processes causes environmental and human health concern. Historically, the use of natural coagulant to purify turbid water has been practiced for a long time. Recent research indicates that Descurainia Sophia seed can be effectively used as a natural coagulant to remove water turbidity. Method: In this work, turbidity removal efficiency of Descurainia Sophia seed extract was compared with Ferric chloride. Experiments were performed in laboratory scale. The coagulation experiments were done with kaolin as a model soil to produce turbidity in distilled water. The turbidity removal efficiency of Descurainia Sophia seed extract and Ferric chloride were conducted with jar test apparatus. In all experiments, initial turbidity was kept constant 100(NTU. Optimum combination of independent variables was used to compare two different types of coagulants. Result: The obtained results showed that Ferric chloride could remove 89.75% of the initial turbidity, while in case of Descurainia Sophia this value was 43.13%. The total organic carbon (TOC analysis of the treated water using seed extract showed an increased concentration of TOC equal to 0.99 mg/L. Conclusions: This research has shown that Descurainia Sophia seed extract has an acceptable potential in the coagulation/flocculation process to treat turbid water.

Turbid releases from Glen Canyon Dam, Arizona, following rainfall-runoff events of September 2013

Science.gov (United States)

Wildman, Richard A.; Vernieu, William

2017-01-01

Glen Canyon Dam is a large dam on the Colorado River in Arizona. In September 2013, it released turbid water following intense thunderstorms in the surrounding area. Turbidity was >15 nephelometric turbidity units (NTU) for multiple days and >30 NTU at its peak. These unprecedented turbid releases impaired downstream fishing activity and motivated a rapid-response field excursion. At 5 locations upstream from the dam, temperature, specific conductance, dissolved oxygen, chlorophyll a, and turbidity were measured in vertical profiles. Local streamflow and rainfall records were retrieved, and turbidity and specific conductance data in dam releases were evaluated. Profiling was conducted to determine possible sources of turbidity from 3 tributaries nearest the dam, Navajo, Antelope, and Wahweap creeks, which entered Lake Powell as interflows during this study. We discuss 4 key conditions that must have been met for tributaries to influence turbidity of dam releases: tributary flows must have reached the dam, tributary flows must have been laden with sediment, inflow currents must have been near the depth of dam withdrawals, and the settling velocity of particles must have been slow. We isolate 2 key uncertainties that reservoir managers should resolve in future similar studies: the reach of tributary water into the reservoir thalweg and the distribution of particle size of suspended sediment. These uncertainties leave the source of the turbidity ambiguous, although an important role for Wahweap Creek is possible. The unique combination of limnological factors we describe implies that turbid releases at Glen Canyon Dam will continue to be rare.

A multilayer approach for turbidity currents

Science.gov (United States)

Fernandez-Nieto, Enrique; Castro Díaz, Manuel J.; Morales de Luna, Tomás

2017-04-01

When a river that carries sediment in suspension enters into a lake or the ocean it can form a plume that can be classified as hyperpycnal or hypopycnal. Hypopycnal plumes occurs if the combined density of the sediment and interstitial fluid is lower than that of the ambient. Hyperpycnal plumes are a class of sediment-laden gravity current commonly referred to as turbidity currents [7,9]. Some layer-averaged models have been previously developed (see [3, 4, 8] among others). Although this layer-averaged approach gives a fast and valuable information, it has the disadvantage that the vertical distribution of the sediment in suspension is lost. A recent technique based on a multilayer approach [1, 2, 6] has shown to be specially useful to generalize shallow water type models in order to keep track of the vertical components of the averaged variables in the classical shallow water equations. In [5] multilayer model is obtained using a vertical discontinuous Galerkin approach for which the vertical velocity is supposed to be piecewise linear and the horizontal velocity is supposed to be piecewise constant. In this work the technique introduced in [5] is generalized to derive a model for turbidity currents. This model allows to simulate hyperpycnal as well as hypopycnal plumes. Several numerical tests will be presented. References [1] E. Audusse, M. Bristeau, B. Perthame, and J. Sainte-Marie. A multilayer Saint-Venant system with mass exchanges for shallow water flows. derivation and numerical validation. ESAIM: Mathematical Modelling and Numerical Analysis, 45(1):169-200, (2010). [2] E. Audusse, M.-O. Bristeau, M. Pelanti, and J. Sainte-Marie. Approximation of the hydrostatic Navier–Stokes system for density stratified flows by a multilayer model: Kinetic interpretation and numerical solution. Journal of Computational Physics, 230(9):3453-3478, (2011). [3] S. F. Bradford and N. D. Katopodes. Hydrodynamics of turbid underflows. i: Formulation and numerical

In situ visualization and data analysis for turbidity currents simulation

Science.gov (United States)

Camata, Jose J.; Silva, Vítor; Valduriez, Patrick; Mattoso, Marta; Coutinho, Alvaro L. G. A.

2018-01-01

Turbidity currents are underflows responsible for sediment deposits that generate geological formations of interest for the oil and gas industry. LibMesh-sedimentation is an application built upon the libMesh library to simulate turbidity currents. In this work, we present the integration of libMesh-sedimentation with in situ visualization and in transit data analysis tools. DfAnalyzer is a solution based on provenance data to extract and relate strategic simulation data in transit from multiple data for online queries. We integrate libMesh-sedimentation and ParaView Catalyst to perform in situ data analysis and visualization. We present a parallel performance analysis for two turbidity currents simulations showing that the overhead for both in situ visualization and in transit data analysis is negligible. We show that our tools enable monitoring the sediments appearance at runtime and steer the simulation based on the solver convergence and visual information on the sediment deposits, thus enhancing the analytical power of turbidity currents simulations.

15 CFR 921.52 - Promotion and coordination of estuarine research.

Science.gov (United States)

2010-01-01

... 15 Commerce and Foreign Trade 3 2010-01-01 2010-01-01 false Promotion and coordination of estuarine research. 921.52 Section 921.52 Commerce and Foreign Trade Regulations Relating to Commerce and... Research Projects § 921.52 Promotion and coordination of estuarine research. (a) NOAA will promote and...

Fundamentals of estuarine physical oceanography

CERN Document Server

Bruner de Miranda, Luiz; Kjerfve, Björn; Castro Filho, Belmiro Mendes de

2017-01-01

This book provides an introduction to the complex system functions, variability and human interference in ecosystem between the continent and the ocean. It focuses on circulation, transport and mixing of estuarine and coastal water masses, which is ultimately related to an understanding of the hydrographic and hydrodynamic characteristics (salinity, temperature, density and circulation), mixing processes (advection and diffusion), transport timescales such as the residence time and the exposure time. In the area of physical oceanography, experiments using these water bodies as a natural laboratory and interpreting their circulation and mixing processes using theoretical and semi-theoretical knowledge are of fundamental importance. Small-scale physical models may also be used together with analytical and numerical models. The book highlights the fact that research and theory are interactive, and the results provide the fundamentals for the development of the estuarine research.

Organizational forms promoting wind power development. Organizational and legal evaluation, energy- and environmental analysis and socio-economic analysis of wind turbine location along railways

International Nuclear Information System (INIS)

1997-12-01

Modernization of the train material and transition from diesel-driven to el-driven trains result in reduced air pollution in Denmark. The purpose of this study is to define, concretize and compare organizational forms for use of wind power as the 'green' electric power for train operation. An investment into an wind turbine array with 500 kW wind turbines in roughness class 2 would be repaid in 7.9 year period. Air pollution abatement together with improved socio-economic structure due to growing employment would be achieved. Several models of 'green' electrification of the national railways are given, both for state- and privately owned wind power plants. (EG)

A Satellite Imagery Approach to Monitor Turbidity and Total Suspended Sediments in Green Bay, WI

Science.gov (United States)

Khazaei, B.; Hamidi, S.; Hosseiny, S. M. H.; Ekhtari, N.

2017-12-01

near the Fox River mouth. It suggests that the main source of sediment in the southern GB is river discharge, even though other factors such as wind driven wave, gyres, and circulation affect the TSS concentration. The proposed approach can be extended to other coastal regions of the Great Lakes and provides a framework to study pollution transportation in coastal areas.

Field Tests of Wind Turbine Unit with Tandem Wind Rotors and Double Rotational Armatures

Science.gov (United States)

Galal, Ahmed Mohamed; Kanemoto, Toshiaki

This paper discusses the field tests of the wind turbine unit, in which the front and the rear wind rotors drive the inner and the outer armatures of the synchronous generator. The wind rotors were designed conveniently by the traditional procedure for the single wind rotor, where the diameters of the front and the rear wind rotors are 2 m and 1.33 m. The tests were done on a pick-up type truck driven straightly at constant speed. The rotational torque of the unit is directly proportional to the induced electric current irrespective of the rotational speeds of the wind rotors, while the induced voltage is proportional to the relative rotational speed. The performance of the unit is significantly affected not only by the wind velocity, but also by the blade setting angles of both wind rotors and the applied load especially at lower wind velocity.

Observable Signatures of Wind-driven Chemistry with a Fully Consistent Three-dimensional Radiative Hydrodynamics Model of HD 209458b

Science.gov (United States)

Drummond, B.; Mayne, N. J.; Manners, J.; Carter, A. L.; Boutle, I. A.; Baraffe, I.; Hébrard, É.; Tremblin, P.; Sing, D. K.; Amundsen, D. S.; Acreman, D.

2018-03-01

We present a study of the effect of wind-driven advection on the chemical composition of hot-Jupiter atmospheres using a fully consistent 3D hydrodynamics, chemistry, and radiative transfer code, the Met Office Unified Model (UM). Chemical modeling of exoplanet atmospheres has primarily been restricted to 1D models that cannot account for 3D dynamical processes. In this work, we couple a chemical relaxation scheme to the UM to account for the chemical interconversion of methane and carbon monoxide. This is done consistently with the radiative transfer meaning that departures from chemical equilibrium are included in the heating rates (and emission) and hence complete the feedback between the dynamics, thermal structure, and chemical composition. In this Letter, we simulate the well studied atmosphere of HD 209458b. We find that the combined effect of horizontal and vertical advection leads to an increase in the methane abundance by several orders of magnitude, which is directly opposite to the trend found in previous works. Our results demonstrate the need to include 3D effects when considering the chemistry of hot-Jupiter atmospheres. We calculate transmission and emission spectra, as well as the emission phase curve, from our simulations. We conclude that gas-phase nonequilibrium chemistry is unlikely to explain the model–observation discrepancy in the 4.5 μm Spitzer/IRAC channel. However, we highlight other spectral regions, observable with the James Webb Space Telescope, where signatures of wind-driven chemistry are more prominant.

40 CFR 141.561 - What happens if my system's turbidity monitoring equipment fails?

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 22 2010-07-01 2010-07-01 false What happens if my system's turbidity... Disinfection-Systems Serving Fewer Than 10,000 People Individual Filter Turbidity Requirements § 141.561 What happens if my system's turbidity monitoring equipment fails? If there is a failure in the continuous...

Concentrations of stable elements and uranium in estuarine areas of Japan

International Nuclear Information System (INIS)

Takata, Hyoe; Aono, Tatsuo; Tagami, Keiko; Uchida, Shigeo

2008-01-01

The geochemistry of stable elements can be a good analogue for understanding the behavior of radionuclides in estuarine and coastal environments. In this study, the behavior of nutrients (NO 3 + NO 2 , PO 4 , Si(OH) 4 ), heavy metals, and U was observed in several estuarine and coastal waters of Japan. We also collected data on salinity, pH, and suspended particle matter (SPM). Nutrient concentrations followed conservative dilution lines in these estuaries, and concentrations of dissolved Fe decreased as salinity increased from 0 to 20. In general, most of the dissolved Fe in estuaries is in colloidal form. The behavior of dissolved Fe might reflect a loss of colloidal Fe through coagulation in this salinity range. Dissolved Co and Ni concentrations followed approximate dilution lines from the rivers to the seawater end-members, suggesting that they were quasi-conservative in these estuarine systems. A rapid increase in dissolved Cd concentrations was observed at low levels of salinity (<4). Estimated fluxes of dissolved Cd to the estuarine and coastal waters showed that the salt-induced desorption of Cd from particles constitutes a significant source of dissolved Cd in the estuarine and coastal waters. (author)

Context-dependent planktivory: interacting effects of turbidity and predation risk on adaptive foraging

Science.gov (United States)

Pangle, Kevin L.; Malinich, Timothy D.; Bunnell, David B.; DeVries, Dennis R.; Ludsin, Stuart A.

2012-01-01

By shaping species interactions, adaptive phenotypic plasticity can profoundly influence ecosystems. Predicting such outcomes has proven difficult, however, owing in part to the dependence of plasticity on the environmental context. Of particular relevance are environmental factors that affect sensory performance in organisms in ways that alter the tradeoffs associated with adaptive phenotypic responses. We explored the influence of turbidity, which simultaneously and differentially affects the sensory performance of consumers at multiple trophic levels, on the indirect effect of a top predator (piscivorous fish) on a basal prey resource (zooplankton) that is mediated through changes in the plastic foraging behavior of an intermediate consumer (zooplanktivorous fish). We first generated theoretical predictions of the adaptive foraging response of a zooplanktivore across wide gradients of turbidity and predation risk by a piscivore. Our model predicted that predation risk can change the negative relationship between intermediate consumer foraging and turbidity into a humped-shaped (unimodal) one in which foraging is low in both clear and highly turbid conditions due to foraging-related risk and visual constraints, respectively. Consequently, the positive trait-mediated indirect effect (TMIE) of the top predator on the basal resource is predicted to peak at low turbidity and decline thereafter until it reaches an asymptote of zero at intermediate turbidity levels (when foraging equals that which is predicted when the top predator is absent). We used field observations and a laboratory experiment to test our model predictions. In support, we found humped-shaped relationships between planktivory and turbidity for several zooplanktivorous fishes from diverse freshwater ecosystems with predation risk. Further, our experiment demonstrated that predation risk reduced zooplanktivory by yellow perch (Perca flavescens) at a low turbidity, but had no effect on consumption at

Data-driven online monitoring of wind turbines

NARCIS (Netherlands)

Kenbeek, T.; Kapodistria, S.; Di Bucchianico, A.

2017-01-01

Condition based maintenance is a modern approach to maintenance which has been successfully used in several industrial sectors. In this paper we present a concrete statistical approach to condition based maintenance for wind turbine by applying ideas from statistical process control. A specific

Advanced control of direct-driven PMSG generator in wind turbine system

Directory of Open Access Journals (Sweden)

Gajewski Piotr

2016-12-01

Full Text Available The paper presents the advanced control system of the wind energy conversion with a variable speed wind turbine. The considered system consists of a wind turbine with the permanent magnet synchronous generator (PMSG, machine side converter (MSC, grid side converter (GSC and control circuits. The mathematical models of a wind turbine system, the PMSG generator and converters have been described. The control algorithms of the converter systems based on the methods of vector control have been applied. In the advanced control system of the machine side converter the optimal MPPT control method has been used. Additionally the pitch control scheme is included in order to achieve the limitation of maximum power and to prevent mechanical damage of the wind turbine. In the control system of the grid side converter the control of active and reactive power has been applied with the application of Voltage Oriented Control (VOC. The performance of the considered wind energy system has been studied by digital simulation. The results of simulation studies confirmed the good effectiveness of the considered wind turbine system and very good performance of the proposed methods of vector control and control systems.

Single shot imaging through turbid medium and around corner using coherent light

Science.gov (United States)

Li, Guowei; Li, Dayan; Situ, Guohai

2018-01-01

Optical imaging through turbid media and around corner is a difficult challenge. Even a very thin layer of a turbid media, which randomly scatters the probe light, can appear opaque and hide any objects behind it. Despite many recent advances, no current method can image the object behind turbid media with single record using coherent laser illumination. Here we report a method that allows non-invasive single-shot optical imaging through turbid media and around corner via speckle correlation. Instead of being as an obstacle in forming diffractionlimited images, speckle actually can be a carrier that encodes sufficient information to imaging through visually opaque layers. Optical imaging through turbid media and around corner is experimentally demonstrated using traditional imaging system with the aid of iterative phase retrieval algorithm. Our method require neither scan of illumination nor two-arm interferometry or long-time exposure in acquisition, which has new implications in optical sensing through common obscurants such as fog, smoke and haze.

Effect of thermal shock on developmental stages of estuarine fish. Final report

International Nuclear Information System (INIS)

Dean, J.M.

1978-12-01

Physiological data and ecological data show that the few estuarine spawners have a higher thermal tolerance in the embryonic and larval stages than do the freshwater, coastal, or oceanic spawning species. However, since all three groups (freshwater, estuarine, and oceanic spawners) occupy the estuary and coastal waters at different times of the year, knowledge of their physiology and ecology at different developmental or life cycle stages is critical for estuarine management decisions

Coagulation effectiveness of graphene oxide for the removal of turbidity from raw surface water.

Science.gov (United States)

Aboubaraka, Abdelmeguid E; Aboelfetoh, Eman F; Ebeid, El-Zeiny M

2017-08-01

This study presents the performance of graphene oxide (GO) as a coagulant in turbidity removal from naturally and artificially turbid raw surface water. GO is considered an excellent alternative to alum, the more common coagulant used in water treatment processes, to reduce the environmental release of aluminum. Effects of GO dosage, pH, and temperature on its coagulation ability were studied to determine the ideal turbidity removal conditions. The turbidity removal was ≥95% for all levels of turbid raw surface water (20, 100, and 200 NTU) at optimum conditions. The role of alkalinity in inducing turbidity removal by GO coagulation was much more pronounced upon using raw surface water samples compared with that using artificially turbid deionized water samples. Moreover, GO demonstrated high-performance removal of biological contaminants such as algae, heterotrophic bacteria, and fecal coliform bacteria by 99.0%, 98.8% and 96.0%, respectively, at a dosage of 40 mg/L. Concerning the possible environmental release of GO into the treated water following filtration process, there was no residual GO in a wide range of pH values. The outcomes of the study highlight the excellent coagulation performance of GO for the removal of turbidity and biological contaminants from raw surface water. Copyright © 2017 Elsevier Ltd. All rights reserved.

Turbidity and suspended sediment in the upper Esopus Creek watershed, Ulster County, New York

Science.gov (United States)

McHale, Michael R.; Siemion, Jason

2014-01-01

Suspended-sediment concentrations (SSCs) and turbidity were measured for 2 to 3 years at 14 monitoring sites throughout the upper Esopus Creek watershed in the Catskill Mountains of New York State. The upper Esopus Creek watershed is part of the New York City water-supply system that supplies water to more than 9 million people every day. Turbidity, caused primarily by high concentrations of inorganic suspended particles, is a potential water-quality concern because it colors the water and can reduce the effectiveness of drinking-water disinfection. The purposes of this study were to quantify concentrations of suspended sediment and turbidity levels, to estimate suspended-sediment loads within the upper Esopus Creek watershed, and to investigate the relations between SSC and turbidity. Samples were collected at four locations along the main channel of Esopus Creek and at all of the principal tributaries. Samples were collected monthly and during storms and were analyzed for SSC and turbidity in the laboratory. Turbidity was also measured every 15 minutes at six of the sampling stations with in situ turbidity probes.

[Experimental research of turbidity influence on water quality monitoring of COD in UV-visible spectroscopy].

Science.gov (United States)

Tang, Bin; Wei, Biao; Wu, De-Cao; Mi, De-Ling; Zhao, Jing-Xiao; Feng, Peng; Jiang, Shang-Hai; Mao, Ben-Jiang

2014-11-01

Eliminating turbidity is a direct effect spectroscopy detection of COD key technical problems. This stems from the UV-visible spectroscopy detected key quality parameters depend on an accurate and effective analysis of water quality parameters analytical model, and turbidity is an important parameter that affects the modeling. In this paper, we selected formazine turbidity solution and standard solution of potassium hydrogen phthalate to study the turbidity affect of UV--visible absorption spectroscopy detection of COD, at the characteristics wavelength of 245, 300, 360 and 560 nm wavelength point several characteristics with the turbidity change in absorbance method of least squares curve fitting, thus analyzes the variation of absorbance with turbidity. The results show, In the ultraviolet range of 240 to 380 nm, as the turbidity caused by particle produces compounds to the organics, it is relatively complicated to test the turbidity affections on the water Ultraviolet spectra; in the visible region of 380 to 780 nm, the turbidity of the spectrum weakens with wavelength increases. Based on this, this paper we study the multiplicative scatter correction method affected by the turbidity of the water sample spectra calibration test, this method can correct water samples spectral affected by turbidity. After treatment, by comparing the spectra before, the results showed that the turbidity caused by wavelength baseline shift points have been effectively corrected, and features in the ultraviolet region has not diminished. Then we make multiplicative scatter correction for the three selected UV liquid-visible absorption spectroscopy, experimental results shows that on the premise of saving the characteristic of the Ultraviolet-Visible absorption spectrum of water samples, which not only improve the quality of COD spectroscopy detection SNR, but also for providing an efficient data conditioning regimen for establishing an accurate of the chemical measurement methods.

Direct Drive Synchronous Machine Models for Stability Assessment of Wind Farms

Energy Technology Data Exchange (ETDEWEB)

Poeller, Markus; Achilles, Sebastian [DIgSILENT GmbH, Gomaringen (Germany)

2003-11-01

The increasing size of wind farms requires power system stability analysis including dynamic wind generator models. For turbines above 1MW doubly-fed induction machines are the most widely used concept. However, especially in Germany, direct-drive wind generators based on converter-driven synchronous generator concepts have reached considerable market penetration. This paper presents converter driven synchronous generator models of various order that can be used for simulating transients and dynamics in a very wide time range.

Changes of turbidity during the phenol oxidation by photo-Fenton treatment.

Science.gov (United States)

Villota, Natalia; Camarero, Luis M; Lomas, Jose M; Perez, Jonatan

2014-11-01

Turbidity presented by phenol solutions oxidized with Fenton reagent shows the tendency of a first order intermediate kinetics. Thus, turbidity can be considered a representative parameter of the presence of intermediate oxidation species, which are generated along the decomposition of toxic and reluctant contaminants, such as phenol. Moreover, that parameter presents a linear dependence with the catalyst dosage, but is also determined by the initial contaminant load. When analyzing the oxidation mechanism of phenol, it is found that the maximum turbidity occurs when the treatment is carried out at oxidant to phenol molar ratios R = 4.0. These oxidation conditions correspond to the presence of a reaction mixture mainly composed of dihydroxylated rings, precursors of the muconic acid formation. The oxidation via "para" comprises the formation reactions of charge transfer complexes (quinhydrone), between the para-dihydroxylated intermediates (hydroquinone) and the para-substituted quinones (p-benzoquinone), which are quite unstable and reactive species, quickly decomposed into hydroxyhydroquinones. Working with oxidant ratios up to R = 6.0, the maximum observed value of turbidity in the oxidized solutions is kept almost constant. It is found that, in these conditions, the pyrogallol formation is maximal, what is generated through the degradation of ortho-species (catechol and ortho-benzoquinone) and meta-substituted (resorcinol). Operating with ratios over R = 6.0, these intermediates are decomposed into biodegradable acids, generating lower turbidity in the solution. Then, the residual turbidity is a function of the molar ratio of the ferrous ions vs. moles of oxidant utilized in the essays, that lets to estimate the stoichiometric dosage of catalyst as 20 mg/L at pH = 3.0, whereas operating in stoichiometric conditions, R = 14.0, the residual turbidity of water results almost null.

Fabrication of an inexpensive photosensitive flow through device for turbidity measurement

International Nuclear Information System (INIS)

Morco, Ryan P.; Dawal, Micah S.; Sucgang, Raymond J.

2014-01-01

The aim of this study is the construction of a portable, simple to use, on-line photosensitive device which measures turbidity in water. The turbidity measuring device uses a light emitting diode, LED, light source shining on a light dependent resistor, LDR, which is connected in series to a circuit supplying a constant voltage and a digital voltmeter, DVM. Light shine through a tube containing the sample, and onto a photosensitive circuit. A clear tube of water is the BLANK and has zero absorbance. A fraction of the incident light that i obstructed by the turbidity of the sample can be used for calculable determination of turbidity in water. The turbidity is related to the absorbance reading, following Beer's law. The amount of incident and transmitted light are expressed in voltage units, by a voltmeter. The sample is delivered into the sampling chamber by a rubber tubing attached to a power head submersible pump which is immersed in the pool of water to be sampled. The instrument shows excellent response over the range o turbidity values (5NTU to 180 NTU). Linearity (R 2= 0.95) has been achieved using the device, working with 6 trials per particular NTU value. The NTU readings of the urbidity meter were calibrated against solutions of varying NTU's measured using a HORIBA multi-parameter probe. The other features of the device include: simplicity of operation, low-cost, rugged, handy and can be used in on-line and flow mode applications. (author)

An analytical two-flow model to simulate the distribution of irradiance in coastal waters with a wind-roughed surface and bottom reflectance

Science.gov (United States)

Ma, Wei-Ming

1997-06-01

An analytical two-flow model is derived from the radiative transfer equation to simulate the distribution of irradiance in coastal waters with a wind-roughed surface and bottom reflectance. The model utilizes unique boundary conditions, including the surface slope of the downwelling and upwelling irradiance as well as the influence of wind and bottom reflectance on simulated surface reflectance. The developed model provides a simple mathematical concept for understanding the irradiant light flux and associated processes in coastal or fresh water as well as turbid estuarine waters. The model is applied to data from the Banana River and coastal Atlantic Ocean water off the east coast of central Florida, USA. The two-flow irradiance model is capable of simulating realistic above-surface reflectance signatures under wind-roughened air-water surface given realistic input parameters including a specular flux conversion coefficient, absorption coefficient, backscattering coefficient, atmospheric visibility, bottom reflectance, and water depth. The root-mean-squared error of the calculated above-surface reflectances is approximately 3% in the Banana River and is less than 15% in coastal Atlantic Ocean off the east of Florida. Result of the subsurface reflectance sensitivity analysis indicates that the specular conversion coefficient is the most sensitive parameter in the model, followed by the beam attenuation coefficient, absorption coefficient, water depth, backscattering coefficient, specular irradiance, diffuse irradiance, bottom reflectance, and wind speed. On the other hand, result of the above-surface reflectance sensitivity analysis indicates that the wind speed is the most important parameter, followed by bottom reflectance, attenuation coefficient, water depth, conversion coefficient, specular irradiance, downwelling irradiance, absorption coefficient, and backscattering coefficient. Model results depend on the accuracy of these parameters to a large degree and

Reversing tidal flow and estuarine morphodynamics in the Metronome laboratory flume

NARCIS (Netherlands)

Kleinhans, M.G.; Leuven, J.R.F.W.; Braat, L.; van der Vegt, M.; van Maarseveen, M.C.G.; Markies, H.; Roosendaal, C.; van Eijk, A.M.

2016-01-01

Our objective is to test a novel experimental principle for creating reversing tidal flows of sufficient strength to cause estuarine morphodynamics. The study of estuarine morphodynamics has hitherto been limited to field observation and numerical modelling, whilst fluvial morphodynamics have

Importance of atmospheric turbidity and associated uncertainties in solar radiation and luminous efficacy modelling

International Nuclear Information System (INIS)

Gueymard, Christian A.

2005-01-01

For many solar-related applications, it is important to separately predict the direct and diffuse components of irradiance or illuminance. Under clear skies, turbidity plays a determinant role in quantitatively affecting these components. In this paper, various aspects of the effect of turbidity on both spectral and broadband radiation are addressed, as well as the uncertainty in irradiance predictions due to inaccurate turbidity data, and the current improvements in obtaining the necessary turbidity data

DUST DYNAMICS IN PROTOPLANETARY DISK WINDS DRIVEN BY MAGNETOROTATIONAL TURBULENCE: A MECHANISM FOR FLOATING DUST GRAINS WITH CHARACTERISTIC SIZES

Energy Technology Data Exchange (ETDEWEB)

Miyake, Tomoya; Suzuki, Takeru K.; Inutsuka, Shu-ichiro, E-mail: miyake.tomoya@e.mbox.nagoya-u.ac.jp, E-mail: stakeru@nagoya-u.jp [Department of Physics, Nagoya University, Nagoya, Aichi 464-8602 (Japan)

2016-04-10

We investigate the dynamics of dust grains of various sizes in protoplanetary disk winds driven by magnetorotational turbulence, by simulating the time evolution of the dust grain distribution in the vertical direction. Small dust grains, which are well-coupled to the gas, are dragged upward with the upflowing gas, while large grains remain near the midplane of a disk. Intermediate-size grains float near the sonic point of the disk wind located at several scale heights from the midplane, where the grains are loosely coupled to the background gas. For the minimum mass solar nebula at 1 au, dust grains with size of 25–45 μm float around 4 scale heights from the midplane. Considering the dependence on the distance from the central star, smaller-size grains remain only in an outer region of the disk, while larger-size grains are distributed in a broader region. We also discuss the implications of our result for observations of dusty material around young stellar objects.

Applications of MODIS Fluorescence Line Height Measurements to Monitor Water Quality Trends and Algal Bloom Activity in Coastal and Estuarine Waters

Science.gov (United States)

Fischer, A.; Ryan, J. P.; Moreno-Madriñán, M. J.

2012-12-01

Recent advances in satellite and airborne remote sensing, such as improvements in sensor and algorithm calibrations and atmospheric correction procedures have provided for increased coverage of remote-sensing, ocean color products for coastal regions. In particular, for the Moderate Resolution Imaging Spectrometer (MODIS), calibration updates, improved aerosol retrievals, and new aerosol models have led to improved atmospheric correction algorithms for turbid waters and have improved the retrieval of ocean-color. This has opened the way for studying coastal ocean phenomena and processes at finer spatial scales. Human population growth and changes in coastal management practices have brought about significant changes in the concentrations of organic and inorganic, particulate and dissolved substances entering the coastal ocean. There is increasing concern that these inputs have led to declines in water quality and increases in local concentrations of phytoplankton, which could result in harmful algal blooms. In two case studies we present improved and validated MODIS coastal observations of fluorescence line height (FLH) to: (1) assess trends in water quality for Tampa Bay, Florida; and (2) illustrate seasonal and annual variability of algal bloom activity in Monterey Bay, California, as well as document estuarine/riverine plume induced red tide events. In a comprehensive analysis of long term (2003-2011) in situ monitoring data and imagery from Tampa Bay, we assess the validity of the MODIS FLH product against chlorophyll-a and a suite of water quality parameters taken in a variety of conditions throughout this large, optically complex estuarine system. A systematic analysis of sampling sites throughout the bay illustrates that the correlations between FLH and in situ chlorophyll-a are influenced by water quality parameters of total nitrogen, total phosphorous, turbidity and biological oxygen demand. Sites that correlated well with satellite imagery were in depths

Historical land-use influences the long-term stream turbidity response to a wildfire.

Science.gov (United States)

Harrison, Evan T; Dyer, Fiona; Wright, Daniel W; Levings, Chris

2014-02-01

Wildfires commonly result in an increase in stream turbidity. However, the influence of pre-fire land-use practices on post-fire stream turbidity is not well understood. The Lower Cotter Catchment (LCC) in south-eastern Australia is part of the main water supply catchment for Canberra with land in the catchment historically managed for a mix of conservation (native eucalypt forest) and pine (Pinus radiata) plantation. In January 2003, wildfires burned almost all of the native and pine forests in the LCC. A study was established in 2005 to determine stream post-fire turbidity recovery within the native and pine forest areas of the catchment. Turbidity data loggers were deployed in two creeks within burned native forest and burned pine forest areas to determine turbidity response to fire in these areas. As a part of the study, we also determined changes in bare soil in the native and pine forest areas since the fire. The results suggest that the time, it takes turbidity levels to decrease following wildfire, is dependent upon the preceding land-use. In the LCC, turbidity levels decreased more rapidly in areas previously with native vegetation compared to areas which were previously used for pine forestry. This is likely because of a higher percentage of bare soil areas for a longer period of time in the ex-pine forest estate and instream stores of fine sediment from catchment erosion during post-fire storm events. The results of our study show that the previous land-use may exert considerable control over on-going turbidity levels following a wildfire.

Natural fluctuations in nearshore turbidity and the relative influences of beach renourishment

OpenAIRE

Dompe, Philip E.

1993-01-01

Turbidity is a measure of the clarity of water. Turbidity depends upon the scattering and absorption of light by suspended particles. The focus of this study was to obtain quantitative measurements of turbidity in the nearshore zone, along with measurements of associated wave parameters and currents occurring naturally and during a beach nourishment project. The objectives were to make quantitative and qualitative comparisons between natural events and those induced by the dred...

Feasibility of turbidity removal by high-gradient superconducting magnetic separation.

Science.gov (United States)

Zeng, Hua; Li, Yiran; Xu, Fengyu; Jiang, Hao; Zhang, Weimin

2015-01-01

Several studies have focused on pollutant removal by magnetic seeding and high-gradient superconducting magnetic separation (HGSMS). However, few works reported the application of HGSMS for treating non-magnetic pollutants by an industrial large-scale system. The feasibility of turbidity removal by a 600 mm bore superconducting magnetic separation system was evaluated in this study. The processing parameters were evaluated by using a 102 mm bore superconducting magnetic separation system that was equipped with the same magnetic separation chamber that was used in the 600 mm bore system. The double-canister system was used to process water pollutants. Analytical grade magnetite was used as a magnetic seed and the turbidity of the simulated raw water was approximately 110 NTU, and the effects of polyaluminum chloride (PAC) and magnetic seeds on turbidity removal were evaluated. The use of more PAC and magnetic seeds had few advantages for the HGSMS at doses greater than 8 and 50 mg/l, respectively. A magnetic intensity of 5.0 T was beneficial for HGSMS, and increasing the flow rate through the steel wool matrix decreased the turbidity removal efficiency. In the breakthrough experiments, 90% of the turbidity was removed when 100 column volumes were not reached. The processing capacity of the 600 mm bore industry-scale superconducting magnetic separator for turbidity treatment was approximately 78.0 m(3)/h or 65.5 × 10(4) m(3)/a. The processing cost per ton of water for the 600 mm bore system was 0.1 $/t. Thus, the HGSMS separator could be used in the following special circumstances: (1) when adequate space is not available for traditional water treatment equipment, especially the sedimentation tank, and (2) when decentralized sewage treatment HGSMS systems are easier to transport and install.

Transient analysis of a grid connected wind driven induction generator using a real-time simulation platform

Energy Technology Data Exchange (ETDEWEB)

Ouhrouche, Mohand [Department of Applied Sciences, University of Quebec at Chicoutimi, Quebec, G7H2B1 (Canada)

2009-03-15

Due to its simple construction, ruggedness and low cost, the induction generator driven by a wind turbine and feeding power to the grid appears to be an attractive solution to the problem of growing energy demand in the context of environmental issues. This paper investigates the integration of such a system into the main utility using RT-Lab trademark (Trademark of Opal-RT Technologies) software package running on a simple off-the-shelf PC. This real-time simulation platform is now adopted by many high-tech industries as a real-time laboratory package for rapid control prototyping and for Hardware-in-the-Loop applications. Real-time digital simulation results obtained during contingencies, such as islanding and unbalanced faults are presented and analysed. (author)

Drinking water turbidity and emergency department visits for gastrointestinal illness in Atlanta, 1993-2004.

Science.gov (United States)

Tinker, Sarah C; Moe, Christine L; Klein, Mitchel; Flanders, W Dana; Uber, Jim; Amirtharajah, Appiah; Singer, Philip; Tolbert, Paige E

2010-01-01

The extent to which drinking water turbidity measurements indicate the risk of gastrointestinal illness is not well understood. Despite major advances in drinking water treatment and delivery, infectious disease can still be transmitted through drinking water in the United States, and it is important to have reliable indicators of microbial water quality to inform public health decisions. The objective of our study was to assess the relationship between gastrointestinal illness, quantified through emergency department visits, and drinking water quality, quantified as raw water and filtered water turbidity measured at the treatment plant. We examined the relationship between turbidity levels of raw and filtered surface water measured at eight major drinking water treatment plants in the metropolitan area of Atlanta, Georgia, and over 240,000 emergency department visits for gastrointestinal illness during 1993-2004 among the population served by these plants. We fit Poisson time-series statistical regression models that included turbidity in a 21-day distributed lag and that controlled for meteorological factors and long-term time trends. For filtered water turbidity, the results were consistent with no association with emergency department visits for gastrointestinal illness. We observed a modest association between raw water turbidity and emergency department visits for gastrointestinal illness. Our results suggest that source water quality may contribute modestly to endemic gastrointestinal illness in the study area. The association between turbidity and emergency department visits for gastrointestinal illness was only observed when raw water turbidity was considered; filtered water turbidity may not serve as a reliable indicator of modest pathogen risk at all treatment plants.

Determination of Residual Chlorine and Turbidity in Drinking Water. Instructor's Manual.

Science.gov (United States)

Office of Water Program Operations (EPA), Cincinnati, OH. National Training and Operational Technology Center.

This instructor's guide presents analytical methods for residual chlorine and turbidity. Topics include sample handling, permissable concentration levels, substitution of residual chlorine for bacteriological work, public notification, and the required analytical techniques to determine residual chlorine and turbidity. This publication is intended…

Determination of Residual Chlorine and Turbidity in Drinking Water. Student Manual.

Science.gov (United States)

Office of Water Program Operations (EPA), Cincinnati, OH. National Training and Operational Technology Center.

This student's manual covers analytical methods for residual chlorine and turbidity. Topics include sample handling, permissable concentration levels, substitution of residual chlorine for bacteriological work, public notification, and the required analytical techniques to determine residual chlorine and turbidity. The publication is intended for…

General assessment of estuarine pollution

Indian Academy of Sciences (India)

First page Back Continue Last page Overview Graphics. General assessment of estuarine pollution. Contamination of estuaries by untreated domestic wastewater is widespread, however, in absence of time-series studies the responses of native flora and fauna to modified environment are unclear. Agricultural runoff ...

Survival of Poliovirus in Flowing Turbid Seawater Treated with Ultraviolet Light

Science.gov (United States)

Hill, W. F.; Hamblet, F. E.; Akin, E. W.

1967-01-01

The effectiveness of a model ultraviolet (UV) radiation unit for treating flowing turbid seawater contaminated with poliovirus was determined. At a turbidity of 70 ppm, the observed survival ratios ranged from 1.9 × 10-3 (99.81% reduction) to 1.5 × 10-4 (99.98% reduction) at flow rates ranging from 25 to 15 liters/min; no virus was recovered at flow rates of 10 and 5 liters/min. At a turbidity of 240 ppm, the observed survival ratios ranged from 3.2 × 10-2 (96.80% reduction) to 2.1 × 10-4 (99.98% reduction) at flow rates ranging from 25 to 5 liters/min. As expected, turbidity had an adverse influence on the effectiveness of UV radiation; however, by adjusting the flow rate of the seawater through the treatment unit, adequate disinfection was shown to be predictable. Images Fig. 1 PMID:4291955

On the rejection of internal and external disturbances in a wind energy conversion system with direct-driven PMSG.

Science.gov (United States)

Li, Shengquan; Zhang, Kezhao; Li, Juan; Liu, Chao

2016-03-01

This paper deals with the critical issue in a wind energy conversion system (WECS) based on a direct-driven permanent magnet synchronous generator (PMSG): the rejection of lumped disturbance, including the system uncertainties in the internal dynamics and unknown external forces. To simultaneously track the motor speed in real time and capture the maximum power, a maximum power point tracking strategy is proposed based on active disturbance rejection control (ADRC) theory. In real application, system inertia, drive torque and some other parameters change in a wide range with the variations of disturbances and wind speeds, which substantially degrade the performance of WECS. The ADRC design must incorporate the available model information into an extended state observer (ESO) to compensate the lumped disturbance efficiently. Based on this principle, a model-compensation ADRC is proposed in this paper. Simulation study is conducted to evaluate the performance of the proposed control strategy. It is shown that the effect of lumped disturbance is compensated in a more effective way compared with the traditional ADRC approach. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

Extending the range of turbidity measurement using polarimetry

Science.gov (United States)

Baba, Justin S.

2017-11-21

Turbidity measurements are obtained by directing a polarized optical beam to a scattering sample. Scattered portions of the beam are measured in orthogonal polarization states to determine a scattering minimum and a scattering maximum. These values are used to determine a degree of polarization of the scattered portions of the beam, and concentrations of scattering materials or turbidity can be estimated using the degree of polarization. Typically, linear polarizations are used, and scattering is measured along an axis that orthogonal to the direction of propagation of the polarized optical beam.

Distribution and diversity of copepods in the Mandovi-Zuari estuarine system, Goa

Digital Repository Service at National Institute of Oceanography (India)

Goswami, S.C.

Truly estuarine and estuarine-marine species were the major components of copepods Neritic and limnetic species were stragglers in this environment and showed fortuitous distribution Monsoonal cycle induced seasonal rhythm on salinity and copepods...

Operating Conditions of Coagulation-Flocculation Process for High Turbidity Ceramic Wastewater

Directory of Open Access Journals (Sweden)

Sameer Al-Asheh

2017-04-01

Full Text Available This work attempted to determine the optimum conditions required for the coagulation and flocculation process as an essential stage of the ceramic wastewater treatment. Coagulation and flocculation is a very necessary step in industries as it lessens turbidity, color, and odor of wastewater. The experimental work was performed in several runs. The volume of wastewater used in each run was 200 mL and was kept at this value throughout. In certain runs, the speed of the mixer was varied while keeping the quantity of coagulant and flocculant constant in order to determine the optimum speed that resulted in the least turbidity. A speed of 5% was chosen as the ideal process speed according to the results obtained. Next, experiments were operated at this optimum speed while changing the dosage of coagulant and flocculant in order to decide the optimum dosage. Coagulant and flocculent amounts of 0.4 g (without booster and 0.2 g (with booster selected after the readings were taken. For all the readings, a turbidity meter was used providing results in Nephelometric Turbidity Units (NTU. Lowest turbidity was achieved when using 5% speed with 0.4 grams of coagulant and 0.4 grams of flocculant, or 5% speed with 0.2 grams of coagulant, 0.2 grams of flocculant and 0.25 g/L of booster coagulant. According to factorial design analysis, such as parameters as impeller speed and dosage have an influential impact on the turbidity; while the booster has insignificant influence and other interactions between parameters are important.

Effects of water turbidity and different temperatures on oxidative stress in caddisfly (Stenopsyche marmorata) larvae.

Science.gov (United States)

Suzuki, Jumpei; Imamura, Masahiro; Nakano, Daisuke; Yamamoto, Ryosuke; Fujita, Masafumi

2018-07-15

Anthropogenic water turbidity derived from suspended solids (SS) is caused by reservoir sediment management practices such as drawdown flushing. Turbid water induces stress in many aquatic organisms, but the effects of turbidity on oxidative stress responses in aquatic insects have not yet been demonstrated. Here, we examined antioxidant responses, oxidative damage, and energy reserves in caddisfly (Stenopsyche marmorata) larvae exposed to turbid water (0 mg SS L -1 , 500 mg SS L -1 , and 2000 mg SS L -1 ) at different temperatures. We evaluated the combined effects of turbid water and temperature by measuring oxidative stress and using metabolic biomarkers. No turbidity level was significantly lethal to S. marmorata larvae. Moreover, there were no significant differences in antioxidant response or oxidative damage between the control and turbid water treatments at a low temperature (10 °C). However, at a high temperature (25 °C), turbid water modulated the activity of the antioxidant enzymes superoxide dismutase and catalase and the oxygen radical absorbance capacity as an indicator of the redox state of the insect larvae. Antioxidant defenses require energy, and high temperature was associated with low energy reserves, which might limit the capability of organisms to counteract reactive oxygen species. Moreover, co-exposure to turbid water and high temperature caused fluctuation of antioxidant defenses and increased the oxidative damage caused by the production of reactive oxygen species. Furthermore, the combined effect of high temperature and turbid water on antioxidant defenses and oxidative damage was larger than the individual effects. Therefore, our results demonstrate that exposure to both turbid water and high temperature generates additive and synergistic interactions causing oxidative stress in this aquatic insect species. Copyright © 2018. Published by Elsevier B.V.

Forest trees filter chronic wind-signals to acclimate to high winds.

Science.gov (United States)

Bonnesoeur, Vivien; Constant, Thiéry; Moulia, Bruno; Fournier, Meriem

2016-05-01

Controlled experiments have shown that trees acclimate thigmomorphogenetically to wind-loads by sensing their deformation (strain). However, the strain regime in nature is exposed to a full spectrum of winds. We hypothesized that trees avoid overreacting by responding only to winds which bring information on local climate and/or wind exposure. Additionally, competition for light dependent on tree social status also likely affects thigmomorphogenesis. We monitored and manipulated quantitatively the strain regimes of 15 pairs of beech (Fagus sylvatica) trees of contrasting social status in an acclimated stand, and quantified the effects of these regimes on the radial growth over a vegetative season. Trees exposed to artificial bending, the intensity of which corresponds to the strongest wind-induced strains, enhanced their secondary growth by at least 80%. Surprisingly, this reaction was even greater - relatively - for suppressed trees than for dominant ones. Acclimated trees did not sense the different types of wind events in the same way. Daily wind speed peaks due to thermal winds were filtered out. Thigmomorphogenesis was therefore driven by intense storms. Thigmomorphogenesis is also likely to be involved in determining social status. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Adaptive Controller for Drive System PMSG in Wind Turbine

Directory of Open Access Journals (Sweden)

Gnanambal

2014-07-01

Full Text Available This paper proposes adaptive Maximum Power Point Tracking (MPPT controller for Permanent Magnet Synchronous Generator (PMSG wind turbine and direct power control for grid side inverter for transformer less integration of wind energy. PMSG wind turbine with two back to back voltage source converters are considered more efficient, used to make real and reactive power control. The optimal control strategy has introduced for integrated control of PMSG Maximum Power Extraction, DC link voltage control and grid voltage support controls. Simulation model using MATLAB Simulink has developed to investigate the performance of proposed control techniques for PMSG wind turbine steady and variable wind conditions. This paper shows that the direct driven grid connected PMSG system has excellent performances and confirms the feasibility of the proposed techniques. While the wind turbine market continues to be dominated by conventional gear-driven wind turbine systems, the direct drive is attracting attention. PM machines are more attractive and superior with higher efficiency and energy yield, higher reliability, and power-to-weight ratio compared with electricity-excited machines.

Removal of colour, turbidity, oil and grease for slaughterhouse wastewater using electrocoagulation method

Science.gov (United States)

Yusoff, Mohd Suffian; Azwan, Azlyza Mohd; Zamri, Mohd Faiz Muaz Ahmad; Aziz, Hamidi Abdul

2017-10-01

In this study electrocoagulation method is used to treat slaughterhouse wastewaters. The aim of this study is to determine the efficiency of electrocoagulation method for the removal of colour, turbidity, oil and grease of slaughterhouse wastewaters. The factors of electrode types, and voltage applied during treatment are the study parameters. The types of electrode used are Aluminium (Al) grade 6082 and Iron (Fe) grade 1050. Meanwhile, the ranges of voltage applied are 2, 4, 6, 8 volts at a time interval of 10, 20 and 30 minutes respectively. The effect of these factors on the removal of fat oil and grease (FOG), colour and turbidity are analyzed. The results show maximum removal of FOG, colour and turbidity are recorded using Fe electrode at 8 V of applied voltage with 30 minutes of treatment time. The increase in treatment time of the cell will also increase the amount of hydrogen bubbles at the cathode which results in a greater upwards flux and a faster removal of FOG,, turbidity and colour. The removal of FOG, colour and turbidity are 98%, 92% and 91 % respectively. Meanwhile, by using Al electrodes in the same condition, the removal of FOG, colour and turbidity are 91%, 85% and 87 % respectively. Whereas by using Fe-Al as electrodes pairs, the removal of FOG, colour and turbidity are found to be at 90%, 87% and 76 % respectively. In this case, the Fe-Fe pair electrodes have been proven to provide better performance for FOG, colour and turbidity removals of slaughterhouse wastewaters. Therefore, it is feasible to be considered as an alternative method for wastewater treatment.

Limitations of turbidity process probes and formazine as their calibration standard.

Science.gov (United States)

Münzberg, Marvin; Hass, Roland; Dinh Duc Khanh, Ninh; Reich, Oliver

2017-01-01

Turbidity measurements are frequently implemented for the monitoring of heterogeneous chemical, physical, or biotechnological processes. However, for quantitative measurements, turbidity probes need calibration, as is requested and regulated by the ISO 7027:1999. Accordingly, a formazine suspension has to be produced. Despite this regulatory demand, no scientific publication on the stability and reproducibility of this polymerization process is available. In addition, no characterization of the optical properties of this calibration material with other optical methods had been achieved so far. Thus, in this contribution, process conditions such as temperature and concentration have been systematically investigated by turbidity probe measurements and Photon Density Wave (PDW) spectroscopy, revealing an influence on the temporal formazine formation onset. In contrast, different reaction temperatures do not lead to different scattering properties for the final formazine suspensions, but give an access to the activation energy for this condensation reaction. Based on PDW spectroscopy data, the synthesis of formazine is reproducible. However, very strong influences of the ambient conditions on the measurements of the turbidity probe have been observed, limiting its applicability. The restrictions of the turbidity probe with respect to scatterer concentration are examined on the basis of formazine and polystyrene suspensions. Compared to PDW spectroscopy data, signal saturation is observed at already low reduced scattering coefficients.

The relationship between turbidity of mouth-rinsed water and oral health status.

Science.gov (United States)

Takeuchi, Susumu; Ueno, Masayuki; Takehara, Sachiko; Pham, Thuy Anh Vu; Hakuta, Chiyoko; Morishima, Seiji; Shinada, Kayoko; Kawaguchi, Yoko

2013-01-01

The purpose of this study was to examine the relationship between turbidity of mouth rinsed water and oral health status such as dental and periodontal conditions, oral hygiene status, flow rate of saliva and oral bacteria. Subjects were 165 patients who visited the Dental Hospital, Tokyo Medical and Dental University. Oral health status, including dental and periodontal conditions, oral hygiene status and flow rate of saliva, was clinically examined. The turbidity was measured with a turbidimeter. Quantification of Fusobacterium spp, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola and total bacteria levels was performed using real-time PCR. The Pearson correlation and multiple regression analysis were used to explore the associations between the turbidity and oral health parameters. The turbidity showed significant correlations with the number of decayed teeth and deep pockets, the plaque index, extent of tongue coating and Fusobacterium spp, P. gingivalis, T. forsythia, T. denticola and total bacteria levels. In a multiple regression model, the turbidity was negatively associated with the flow rate of saliva and positively associated with the total number of bacteria (p turbidity of mouth rinsed water could be used as an indicator to evaluate oral health condition and the amount of bacteria in the oral cavity. In addition, the turbiditimeter appeared as a simple and objective device for screening abnormality of oral health condition at chair side as well as community-based research.

Stratified magnetically driven accretion-disk winds and their relations to jets

International Nuclear Information System (INIS)

Fukumura, Keigo; Tombesi, Francesco; Kazanas, Demosthenes; Shrader, Chris; Behar, Ehud; Contopoulos, Ioannis

2014-01-01

We explore the poloidal structure of two-dimensional magnetohydrodynamic (MHD) winds in relation to their potential association with the X-ray warm absorbers (WAs) and the highly ionized ultra-fast outflows (UFOs) in active galactic nuclei (AGNs), in a single unifying approach. We present the density n(r, θ), ionization parameter ξ(r, θ), and velocity structure v(r, θ) of such ionized winds for typical values of their fluid-to-magnetic flux ratio, F, and specific angular momentum, H, for which wind solutions become super-Alfvénic. We explore the geometrical shape of winds for different values of these parameters and delineate the values that produce the widest and narrowest opening angles of these winds, quantities necessary in the determination of the statistics of AGN obscuration. We find that winds with smaller H show a poloidal geometry of narrower opening angles with their Alfvén surface at lower inclination angles and therefore they produce the highest line of sight (LoS) velocities for observers at higher latitudes with the respect to the disk plane. We further note a physical and spatial correlation between the X-ray WAs and UFOs that form along the same LoS to the observer but at different radii, r, and distinct values of n, ξ, and v consistent with the latest spectroscopic data of radio-quiet Seyfert galaxies. We also show that, at least in the case of 3C 111, the winds' pressure is sufficient to contain the relativistic plasma responsible for its radio emission. Stratified MHD disk winds could therefore serve as a unique means to understand and unify the diverse AGN outflows.

Evaluation of the Influence of Wind-Driven Rain on Moisture in Cellular Concrete Wall Boards

Directory of Open Access Journals (Sweden)

Alsabry A.

2017-08-01

Full Text Available The non-stationary moisture level of a cellular concrete wall board in a heated utility building located in the northern part of the town of Brest (Belarus, depending on the climatic influence, was assessed in this work. The results were obtained both in a calculation experiment and a physical test. It was observed that the main reason for the high moisture levels in cellular concrete is wind-driven rain intensifying the process of free capillary moisture transfer. A comparative analysis of the results of the physical test and the calculation experiment showed that the THSS software elaborated by the authors was able to predict the actual moisture levels of the shielding structure under study accurately enough when precise data concerning the thermal and physical characteristics of the materials as well as the occurring climatic influences were submitted.

Evaluation of the Influence of Wind-Driven Rain on Moisture in Cellular Concrete Wall Boards

Science.gov (United States)

Alsabry, A.; Nikitsin, V. I.; Kofanov, V. A.; Backiel-Brzozowska, B.

2017-08-01

The non-stationary moisture level of a cellular concrete wall board in a heated utility building located in the northern part of the town of Brest (Belarus), depending on the climatic influence, was assessed in this work. The results were obtained both in a calculation experiment and a physical test. It was observed that the main reason for the high moisture levels in cellular concrete is wind-driven rain intensifying the process of free capillary moisture transfer. A comparative analysis of the results of the physical test and the calculation experiment showed that the THSS software elaborated by the authors was able to predict the actual moisture levels of the shielding structure under study accurately enough when precise data concerning the thermal and physical characteristics of the materials as well as the occurring climatic influences were submitted.

An inversion of the estuarine circulation by sluice water discharge and its impact on suspended sediment transport

Science.gov (United States)

Schulz, Kirstin; Gerkema, Theo

2018-01-01

The Wadden Sea is characterized by a complex topography of branching channels and intertidal flats, in which the interplay between fresh water discharges, wind forcing and the tidal current causes sediment transport rates and direction to be highly variable in space and time. During three field campaigns, indications of a negative estuarine circulation have been found in a channel adjacent to the coast in the Western Dutch Wadden Sea. Contrary to the classical picture of estuarine circulation, a periodic density stratification was observed that builds up during flood and breaks down during ebb. This can be related to a large freshwater source at the mouth of the channel, the sluice in Kornwerderzand. In this study, observations of this phenomenon are presented, and with the help of a numerical model the different drivers for residual suspended matter transport in this area, namely tidal asymmetries in the current velocity and the above mentioned periodic stratification, are investigated. It is found that the residual current in the area of interest points in ebb direction, caused by both the elongated ebb flow phase and the periodic stratification. On the contrary, the stronger flood currents cause a transport of suspended matter in flood direction. This transport is counteracted and therefore diminished by the effects of the sluice discharge.

Concurrent monitoring of vessels and water turbidity enhances the strength of evidence in remotely sensed dredging impact assessment

NARCIS (Netherlands)

Wu, G.; Leeuw, de J.; Skidmore, A.K.; Prins, H.H.T.; Liu, Y.

2007-01-01

Remotely sensed assessment of dredging impacts on water turbidity is straightforward when turbidity plumes show up in clear water. However, it is more complicated in turbid waters as the spatial or temporal changes in turbidity might be of natural origin. The plausibility of attributing turbidity

Bifocal optical coherenc refractometry of turbid media.

Science.gov (United States)

Alexandrov, Sergey A; Zvyagin, Andrei V; Silva, K K M B Dilusha; Sampson, David D

2003-01-15

We propose and demonstrate a novel technique, which we term bifocal optical coherence refractometry, for the rapid determination of the refractive index of a turbid medium. The technique is based on the simultaneous creation of two closely spaced confocal gates in a sample. The optical path-length difference between the gates is measured by means of low-coherence interferometry and used to determine the refractive index. We present experimental results for the refractive indices of milk solutions and of human skin in vivo. As the axial scan rate determines the acquisition time, which is potentially of the order of tens of milliseconds, the technique has potential for in vivo refractive-index measurements of turbid biological media under dynamic conditions.

BOOK REVIEW: ESTUARINE SCIENCE: A SYNTHETIC APPROACH TO RESEARCH AND PRACTICE

Science.gov (United States)

This book is the product of fifty leading estuarine scientists most of whom attended a workshop convened for the purpose of "put[ting] together the case for synthesis of estuarine data and to show the capabilities of synthetic methods of research" (p. 2). The editor, John E. Hob...

Innovation paths in wind power

DEFF Research Database (Denmark)

Lema, Rasmus; Nordensvärd, Johan; Urban, Frauke

Denmark and Germany both make substantial investments in low carbon innovation, not least in the wind power sector. These investments in wind energy are driven by the twin objectives of reducing carbon emissions and building up international competitive advantage. Support for wind power dates back....... The ‘Danish Design’ remains the global standard. The direct drive design, while uncommon in Denmark, dominates the German installation base. Direct drive technology has thus emerged as a distinctly German design and sub-trajectory within the overall technological innovation path. When it comes to organising...... global interconnectedness of wind technology markets and the role of emerging new players, such as China and India....

Impact of Neutrino Flavor Oscillations on the Neutrino-driven Wind Nucleosynthesis of an Electron-capture Supernova

Science.gov (United States)

Pllumbi, Else; Tamborra, Irene; Wanajo, Shinya; Janka, Hans-Thomas; Hüdepohl, Lorenz

2015-08-01

Neutrino oscillations, especially to light sterile states, can affect nucleosynthesis yields because of their possible feedback effect on the electron fraction (Ye). For the first time, we perform nucleosynthesis calculations for neutrino-driven wind trajectories from the neutrino-cooling phase of an 8.8 {M}⊙ electron-capture supernova (SN), whose hydrodynamic evolution was computed in spherical symmetry with sophisticated neutrino transport and whose Ye evolution was post-processed by including neutrino oscillations between both active and active-sterile flavors. We also take into account the α-effect as well as weak magnetism and recoil corrections in the neutrino absorption and emission processes. We observe effects on the Ye evolution that depend in a subtle way on the relative radial positions of the sterile Mikheyev-Smirnov-Wolfenstein resonances, on collective flavor transformations, and on the formation of α particles. For the adopted SN progenitor, we find that neutrino oscillations, also to a sterile state with eV mass, do not significantly affect the element formation and in particular cannot make the post-explosion wind outflow neutron-rich enough to activate a strong r-process. Our conclusions become even more robust when, in order to mimic equation-of-state-dependent corrections due to nucleon potential effects in the dense-medium neutrino opacities, six cases with reduced Ye in the wind are considered. In these cases, despite the conversion of active neutrinos to sterile neutrinos, Ye increases or is not significantly lowered compared to the values obtained without oscillations and active flavor transformations. This is a consequence of a complicated interplay between sterile-neutrino production, neutrino-neutrino interactions, and α-effect.

Potential of turbidity monitoring for real time control of pollutant discharge in sewers during rainfall events.

Science.gov (United States)

Lacour, C; Joannis, C; Gromaire, M-C; Chebbo, G

2009-01-01

Turbidity sensors can be used to continuously monitor the evolution of pollutant mass discharge. For two sites within the Paris combined sewer system, continuous turbidity, conductivity and flow data were recorded at one-minute time intervals over a one-year period. This paper is intended to highlight the variability in turbidity dynamics during wet weather. For each storm event, turbidity response aspects were analysed through different classifications. The correlation between classification and common parameters, such as the antecedent dry weather period, total event volume per impervious hectare and both the mean and maximum hydraulic flow for each event, was also studied. Moreover, the dynamics of flow and turbidity signals were compared at the event scale. No simple relation between turbidity responses, hydraulic flow dynamics and the chosen parameters was derived from this effort. Knowledge of turbidity dynamics could therefore potentially improve wet weather management, especially when using pollution-based real-time control (P-RTC) since turbidity contains information not included in hydraulic flow dynamics and not readily predictable from such dynamics.

Estuarine consumers utilize marine, estuarine and terrestrial organic matter and provide connectivity among these food webs

Science.gov (United States)

The flux of organic matter (OM) across ecosystem boundaries can influence estuarine food web dynamics and productivity. However, this process is seldom investigated taking into account all the adjacent ecosystems (e.g. ocean, river, land) and different hydrological settings (i.e....

The enigmatic ultra-long run-out of seafloor density driven flows

Science.gov (United States)

Dorrell, R. M.

2017-12-01

Dilute, particulate-laden, density-driven flows - turbidity currents - are a predominant mechanism for transporting sediment from source to sink in deep marine environments. These flows sculpt channels on the seafloor and, as evidenced by a wealth of bathymetric data, can travel for >1000km, forming some of the largest sedimentary landforms on the planet. For turbidity currents to travel such large dsitances, sediment must be self-maintained in suspension, i.e., be in a state of autosuspension. It has been shown that such self-maintained sediment suspensions can only occur whilst inertial forces are greater than gravitational forces, entailing supercritical flow. This conclusion is paradoxical, as inertia dominated flows rapidly entrain fluid, thereby thickening and slowing to become subcritical. However, current theory can only truly be applied to the proximal upper slope regions of seafloor channels where incised flows are fully confined. This contrasts with the distal reaches of long run out turbidity current systems, where the flow is only partially confined through self-channelization. Here it is shown that overspill of partially confined flow has a significant effect on the hydro- and morphodynamics of turbidity current systems. A new model is derived that shows that channel overspill acts to negate the effects of ambient fluid entrainment: a dynamic balance that limits increases in flow depth and maintains supercritical flow throughout the channel. In the new model mass, momentum and energy conservation is modulated by flow overspill onto channel banks, necessarily requiring description of the vertical structure of the flow. Analysis of continuously stratified steady state flow dynamics shows that the integration of overspill and stratification is necessary to enable maintained autosuspension and thus predict the ultra-long run-out of turbidity currents.

Using data-driven approach for wind power prediction: A comparative study

International Nuclear Information System (INIS)

Taslimi Renani, Ehsan; Elias, Mohamad Fathi Mohamad; Rahim, Nasrudin Abd.

2016-01-01

Highlights: • Double exponential smoothing is the most accurate model in wind speed prediction. • A two-stage feature selection method is proposed to select most important inputs. • Direct prediction illustrates better accuracy than indirect prediction. • Adaptive neuro fuzzy inference system outperforms data mining algorithms. • Random forest performs the worst compared to other data mining algorithm. - Abstract: Although wind energy is intermittent and stochastic in nature, it is increasingly important in the power generation due to its sustainability and pollution-free. Increased utilization of wind energy sources calls for more robust and efficient prediction models to mitigate uncertainties associated with wind power. This research compares two different approaches in wind power forecasting which are indirect and direct prediction methods. In indirect method, several times series are applied to forecast the wind speed, whereas the logistic function with five parameters is then used to forecast the wind power. In this study, backtracking search algorithm with novel crossover and mutation operators is employed to find the best parameters of five-parameter logistic function. A new feature selection technique, combining the mutual information and neural network is proposed in this paper to extract the most informative features with a maximum relevancy and minimum redundancy. From the comparative study, the results demonstrate that, in the direct prediction approach where the historical weather data are used to predict the wind power generation directly, adaptive neuro fuzzy inference system outperforms five data mining algorithms namely, random forest, M5Rules, k-nearest neighbor, support vector machine and multilayer perceptron. Moreover, it is also found that the mean absolute percentage error of the direct prediction method using adaptive neuro fuzzy inference system is 1.47% which is approximately less than half of the error obtained with the

Effects of turbidity and prey density on the foraging success of age 0 year yellow perch Perca flavescens.

Science.gov (United States)

Wellington, C G; Mayer, C M; Bossenbroek, J M; Stroh, N A

2010-05-01

Laboratory experiments were conducted to determine how larval and juvenile yellow perch Perca flavescens respond to changes in prey density when exposed to different levels and types of turbidity (phytoplanktonic or sedimentary). Across prey densities, consumption by P. flavescens tended to be less in phytoplanktonic turbidity compared with sedimentary turbidity. For larvae, this effect was dependent on turbidity level (consumption differed between turbidity types only at high turbidity), while for juveniles the difference with turbidity type was equal across turbidity levels. These results suggest that phytoplankton blooms are detrimental to the ability of late season age 0 year P. flavescens to forage and support the need to control factors leading to excessive phytoplankton growth in lakes.

Multi-scale wind erosion monitoring and assessment for US rangelands

Science.gov (United States)

Wind erosion is a major resource concern for rangeland managers. Although wind erosion is a naturally occurring process in many drylands, land use activities, and land management in particular, can accelerate wind-driven soil loss – impacting ecosystem dynamics and agricultural production, air quali...

Substorm Occurrence and Intensity Associated With Three Types of Solar Wind Structure

Science.gov (United States)

Liou, Kan; Sotirelis, Thomas; Richardson, Ian

2018-01-01

This paper presents the results of a study of the characteristics of substorms that occurred during three distinct types of solar wind: coronal mass ejection (CME) associated, high-speed streams (HSS), and slow solar wind (SSW). A total number of 53,468 geomagnetic substorm onsets from 1983 to 2009 is used and sorted by the three solar wind types. It is found that the probability density function (PDF) of the intersubstorm time can be fitted by the combination of a dominant power law with an exponential cutoff component and a minor lognormal component, implying that substorms are associated with two distinctly different dynamical processes corresponding, perhaps, to the "externally driven" and "internally driven" processes, respectively. We compare substorm frequency and intensity associated with the three types of solar wind. It is found that the intersubstorm time is the longest during SSW and shortest during CME intervals. The averaged intersubstorm time for the internally driven substorms is 3.13, 3.15, and 7.96 h for CME, HSS, and SSW, respectively. The substorm intensity PDFs, as represented by the peak value of |SML| (the generalization of AL), can be fitted by two lognormal distribution functions. The averaged substorm intensity for either component is largest for CME (292 and 674 nT) and smallest for SSW (265 and 434 nT). We argue that the externally driven substorms are more intense than those driven internally. We conclude that the dynamical process of substorms is controlled mainly by the direct solar wind-magnetosphere coupling, whereas the internally driven process only plays a very modest minor role.

MassFLOW-3D as a simulation tool for turbidity currents

NARCIS (Netherlands)

Basani, Riccardo; Janocko, Michal; Cartigny, Matthieu J.B.; Hansen, Ernst W.M.; Eggenhuisen, Joris T.

2014-01-01

Turbidity currents are the most important mechanism for the dispersal and deposition of sand in the deep-sea setting and thus the main phenomenon leading to the formation of oil and gas reservoirs in deep water deposits. The flow characteristics of turbidity currents are difficult to observe and

Smooth Particle Hydrodynamics-based Wind Representation

Energy Technology Data Exchange (ETDEWEB)

Prescott, Steven [Idaho National Lab. (INL), Idaho Falls, ID (United States); Smith, Curtis [Idaho National Lab. (INL), Idaho Falls, ID (United States); Hess, Stephen [Idaho National Lab. (INL), Idaho Falls, ID (United States); Lin, Linyu [Idaho National Lab. (INL), Idaho Falls, ID (United States); Sampath, Ram [Idaho National Lab. (INL), Idaho Falls, ID (United States)

2016-12-01

As a result of the 2011 accident at the Fukushima Dai-ichi NPP and other operational NPP experience, there is an identified need to better characterize and evaluate the potential impacts of externally generated hazards on NPP safety. Due to the ubiquitous occurrence of high winds around the world and the possible extreme magnitude of the hazard that has been observed, the assessment of the impact of the high-winds hazard has been identified as an important activity by both NPP owner-operators and regulatory authorities. However, recent experience obtained from the conduct of high-winds risk assessments indicates that such activities have been both labor-intensive and expensive to perform. Additionally, the existing suite of methods and tools to conduct such assessments (which were developed decades ago) do not make use of modern computational architectures (e.g., parallel processing, object-oriented programming techniques, or simple user interfaces) or methods (e.g., efficient and robust numerical-solution schemes). As a result, the current suite of methods and tools will rapidly become obsolete. Physics-based 3D simulation methods can provide information to assist in the RISMC PRA methodology. This research is intended to determine what benefits SPH methods could bring to high-winds simulations for the purposes of assessing their potential impact on NPP safety. The initial investigation has determined that SPH can simulate key areas of high-wind events with reasonable accuracy, compared to other methods. Some problems, such as simulation voids, need to be addressed, but possible solutions have been identified and will be tested with continued work. This work also demonstrated that SPH simulations can provide a means for simulating debris movement; however, further investigations into the capability to determine the impact of high winds and the impacts of wind-driven debris that lead to SSC failures need to be done. SPH simulations alone would be limited in size

Pollution biomarkers in estuarine animals: critical review and new perspectives.

Science.gov (United States)

Monserrat, José M; Martínez, Pablo E; Geracitano, Laura A; Amado, Lílian Lund; Martins, Camila Martinez Gaspar; Pinho, Grasiela Lopes Leães; Chaves, Isabel Soares; Ferreira-Cravo, Marlize; Ventura-Lima, Juliane; Bianchini, Adalto

2007-01-01

In this review, recent developments in monitoring toxicological responses in estuarine animals are analyzed, considering the biomarker responses to different classes of pollutants. The estuarine environment imposes stressful conditions to the organisms that inhabit it, and this situation can alter their sensitivity to many pollutants. The specificity of some biomarkers like metallothionein tissue concentration is discussed in virtue of its dependence on salinity, which is highly variable in estuaries. Examples of cholinesterase activity measurements are also provided and criteria to select sensitive enzymes to detect pesticides and toxins are discussed. Regarding non-specific biomarkers, toxic responses in terms of antioxidant defenses and/or oxidative damage are also considered in this review, focusing on invertebrate species. In addition, the presence of an antioxidant gradient along the body of the estuarine polychaete Laeonereis acuta (Nereididae) and its relationship to different strategies, which deal with the generation of oxidative stress, is reviewed. Also, unusual antioxidant defenses against environmental pro-oxidants are discussed, including the mucus secreted by L. acuta. Disruption of osmoregulation by pollutants is of paramount importance in several estuarine species. In some cases such as in the estuarine crab Chasmagnathus granulatus, there is a trade off between bioavailability of toxicants (e.g. metals) and their interaction with key enzymes such as Na(+)-K(+)-ATPase and carbonic anhydrase. Thus, the metal effect on osmoregulation is also discussed in the present review. Finally, field case studies with fish species like the croaker Micropogonias furnieri (Scianidae) are used to illustrate the application of DNA damage and immunosuppressive responses as potential biomarkers of complex mixture of pollutants.

Enhancing the numerical aperture of lenses using ZnO nanostructure-based turbid media

International Nuclear Information System (INIS)

Khokhra, Richa; Barman, Partha Bir; Kumar, Rajesh; Kumar, Manoj; Rawat, Nitin; Jang, Hwanchol; Lee, Heung-No

2013-01-01

Nanosheets, nanoparticles, and microstructures of ZnO were synthesized via a wet chemical method. ZnO films with a thickness of 44–46 μm were fabricated by spray coating, and these have been investigated for their potential use in turbid lens applications. A morphology-dependent comparative study of the transmittance of ZnO turbid films was conducted. Furthermore, these ZnO turbid films were used to enhance the numerical aperture (NA) of a Nikon objective lens. The variation in NA with different morphologies was explained using size-dependent scattering by the fabricated films. A maximum NA of around 1.971 of the objective lens with a turbid film of ZnO nanosheets was achieved. (paper)

Pyrheliometric determination of atmospheric turbidity in harmattan over Ile-Ife, Nigeria

International Nuclear Information System (INIS)

Adeyefa, Z.D.; Adedokun, J.A.

1990-02-01

Measurements of direct solar radiation intensity, using an Angstrom compensation pyrheliometer carried out over three harmattan seasons (1985-1987) at Ile-Ife (7.29N, 4.34E) Nigeria, have been used to determine atmospheric turbidity based on five different models of turbidity, viz: Schuepp (B), Angstrom (β), Kastrov (C), Unsworth (τ a ) and Linke (T). The five parameters indicate high aerosol loading of the atmosphere during the period and high correlation is established between them: (0.919 ≤ τ ≤ 0.999). An inverse relationship has been noticed between horizontal visibility and atmospheric turbidity: (-0.80 ≤ τ ≤ -0.76). (author). 35 refs, 15 figs, 4 tabs

Flow-driven simulation on variation diameter of counter rotating wind turbines rotor

Directory of Open Access Journals (Sweden)

Littik Y. Fredrika

2018-01-01

Full Text Available Wind turbines model in this paper developed from horizontal axis wind turbine propeller with single rotor (HAWT. This research aims to investigating the influence of front rotor diameter variation (D1 with rear rotor (D2 to the angular velocity optimal (ω and tip speed ratio (TSR on counter rotating wind turbines (CRWT. The method used transient 3D simulation with computational fluid dynamics (CFD to perform the aerodynamics characteristic of rotor wind turbines. The counter rotating wind turbines (CRWT is designed with front rotor diameter of 0.23 m and rear rotor diameter of 0.40 m. In this research, the wind velocity is 4.2 m/s and variation ratio between front rotor and rear rotor (D1/D2 are 0.65; 0.80; 1.20; 1.40; and 1.60 with axial distance (Z/D2 0.20 m. The result of this research indicated that the variation diameter on front rotor influence the aerodynamics performance of counter rotating wind turbines.

Tributyltin-resistant bacteria from estuarine and freshwater sediments.

Science.gov (United States)

Wuertz, S; Miller, C E; Pfister, R M; Cooney, J J

1991-01-01

Resistance to tributyltin (TBT) was examined in populations from TBT-polluted sediments and nonpolluted sediments from an estuary and from fresh water as well as in pure cultures isolated from those sediments. The 50% effective concentrations (EC50s) for populations were higher at a TBT-polluted freshwater site than at a site without TBT, suggesting that TBT selected for a TBT-resistant population. In contrast, EC50s were significantly lower for populations from a TBT-contaminated estuarine site than for those from a site without TBT, suggesting that other factors in addition to TBT determine whether populations become resistant. EC50s for populations from TBT-contaminated freshwater sediments were nearly 30 times higher than those for populations from TBT-contaminated estuarine sediments. We defined a TBT-resistant bacterium as one which grows on trypticase soy agar containing 8.4 microM TBT, a concentration which prevented the growth of 90% of the culturable bacteria from these sediments. The toxicity of TBT in laboratory media was influenced markedly by the composition of the medium and whether it was liquid or solid. Ten TBT-resistant isolates from estuarine sediments and 19 from freshwater sediments were identified to the genus level. Two isolates, each a Bacillus sp., may be the first gram-positive bacteria isolated from fresh water in the presence of a high concentration of TBT. There was a high incidence of resistance to heavy metals: metal resistance indices were 0.76 for estuarine isolates and 0.68 for freshwater isolates.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1746939

Extraction of natural coagulant from peanut seeds for treatment of turbid water

International Nuclear Information System (INIS)

Birima, A H; Desa, M N M; Muda, Z C; Hammad, H A

2013-01-01

This study investigates the potential of peanut seeds as an environmental friendly and natural coagulant for the treatment of high turbid water. The peanut seeds have been used after oil extraction; and the active coagulation component was extracted by distilled water and salt solution of different salt concentrations. The salts used were NaCl, KNO 3 , KCl, NH 4 Cl and NaNO 3 . Synthetic water with 200 NTU turbidity was used. Peanut extracted with NaCl (PC-NaCl) could effectively remove 92% of the 200 NTU turbidity using only 20 mg/l, while peanut seeds extracted with distilled water (PC-DW) could remove only 31.5% of the same turbidity with the same dosage. The coagulant dosage did not affected by the concentration of the salt solution, however, residual turbidity decreased with increasing the concentration of the salt; and the relationship was found to be a second order polynomial curve with R 2 of 0.9312. The other salts tested were also found to be good solvents to extract the active coagulation component with no much difference from NaCl solution in terms of efficiency.

The design of rapid turbidity measurement system based on single photon detection techniques

Science.gov (United States)

Yang, Yixin; Wang, Huanqin; Cao, Yangyang; Gui, Huaqiao; Liu, Jianguo; Lu, Liang; Cao, Huibin; Yu, Tongzhu; You, Hui

2015-10-01

A new rapid turbidity measurement system has been developed to measure the turbidity of drinking water. To determinate the turbidity quantitatively, the total intensity of scattering light has been measured and quantified as number of photons by adopting the single photon detection techniques (SPDT) which has the advantage of high sensitivity. On the basis of SPDT, the measurement system has been built and series of experiments have been carried out. Combining then the 90° Mie scattering theory with the principle of SPDT, a turbidity measurement model has been proposed to explain the experimental results. The experimental results show that a turbidity, which is as low as 0.1 NTU (Nephelometric Turbidity Units), can be measured steadily within 100 ms. It also shows a good linearity and stability over the range of 0.1-400 NTU and the precision can be controlled within 5% full scale. In order to improve its precision and stability, some key parameters, including the sampling time and incident light intensity, have been discussed. It has been proved that, to guarantee an excellent system performance, a good compromise between the measurement speed and the low power consumption should be considered adequately depending on the practical applications.

Abrupt state change of river water quality (turbidity): Effect of extreme rainfalls and typhoons.

Science.gov (United States)

Lee, Chih-Sheng; Lee, Yi-Chao; Chiang, Hui-Min

2016-07-01

River turbidity is of dynamic nature, and its stable state is significantly changed during the period of heavy rainfall events. The frequent occurrence of typhoons in Taiwan has caused serious problems in drinking water treatment due to extremely high turbidity. The aim of the present study is to evaluate impact of typhoons on river turbidity. The statistical methods used included analyses of paired annual mean and standard deviation, frequency distribution, and moving standard deviation, skewness, and autocorrelation; all clearly indicating significant state changes of river turbidity. Typhoon Morakot of 2009 (recorded high rainfall over 2000mm in three days, responsible for significant disaster in southern Taiwan) is assumed as a major initiated event leading to critical state change. In addition, increasing rate of turbidity in rainfall events is highly and positively correlated with rainfall intensity both for pre- and post-Morakot periods. Daily turbidity is also well correlated with daily flow rate for all the eleven events evaluated. That implies potential prediction of river turbidity by river flow rate during rainfall and typhoon events. Based on analysis of stable state changes, more effective regulations for better basin management including soil-water conservation in watershed are necessary. Furthermore, municipal and industrial water treatment plants need to prepare and ensure the adequate operation of water treatment with high raw water turbidity (e.g., >2000NTU). Finally, methodology used in the present of this study can be applied to other environmental problems with abrupt state changes. Copyright © 2016 Elsevier B.V. All rights reserved.

Optics of turbid slabs

International Nuclear Information System (INIS)

Kokhanovsky, A.A.

2002-01-01

This paper is devoted to an alternative derivation of the asymptotic equations for the reflection and transmission functions of turbid slabs. The derivation is based on the reciprocity principle and the law of conservation of energy. Thus it is very general. This allows us to apply the obtained equations even in cases where the foundations of the radiative transfer theory are in question (e.g. for highly concentrated suspensions and pastes). (author)

Estuarine and marine geology (2011-2015)

Digital Repository Service at National Institute of Oceanography (India)

Rao, V.P.; Chakraborty, P.

. Detailed studies on rock-magnetic properties and delta 13C_org in sediments off the Krishna-Godavari provide evidence of reductive diagenesis, formation of authigenic sulfides and occurrence of methane in these estuarine sediments and also...

Solar wind power electric plant on Vis (Croatia)

International Nuclear Information System (INIS)

1998-01-01

A project of a solar photovoltaic electric power plant presented by the Republic of Croatia at the meeting of the E.P.I.A. Mission for photovoltaic technology of the Mediterranean countries, aroused a great interest of the representatives of the invited countries. However, the interest within Croatia in the project has disappeared although E.P.I.A. offered a financing of two thirds of costs. There are attempts to construct 1800 kw wind-driven generators at the same location not taking into consideration a possibility of building a hybrid solar-wind-power electric plant. The chance that the solar part is completely of domestic origin is not accepted but the preference is given to the building of imported wind-driven generators. (orig.)

40 CFR 141.551 - What strengthened combined filter effluent turbidity limits must my system meet?

Science.gov (United States)

2010-07-01

... effluent turbidity limits must my system meet? 141.551 Section 141.551 Protection of Environment... Effluent Requirements § 141.551 What strengthened combined filter effluent turbidity limits must my system meet? Your system must meet two strengthened combined filter effluent turbidity limits. (a) The first...

Recovering low-turbidity cutting liquid from silicon slurry waste.

Science.gov (United States)

Tsai, Tzu-Hsuan; Shih, Yu-Pei

2014-04-30

In order to recover a low-turbidity polyalkylene glycol (PAG) liquid from silicon slurry waste by sedimentation, temperatures were adjusted, and acetone, ethanol or water was used as a diluent. The experimental results show that the particles in the waste would aggregate and settle readily by using water as a diluent. This is because particle surfaces had lower surface potential value and weaker steric stabilization in PAG-water than in PAG-ethanol or PAG-acetone solutions. Therefore, water is the suggested diluent for recovering a low-turbidity PAG (sedimentation. After 50 wt.% water-assisted sedimentation for 21 days, the solid content of the upper liquid reduced to 0.122 g/L, and the turbidity decreased to 44 NTU. The obtained upper liquid was then vacuum-distillated to remove water. The final recovered PAG with 0.37 NTU had similar viscosity and density to the unused PAG and could be reused in the cutting process. Copyright © 2014 Elsevier B.V. All rights reserved.

USING TURBIDITY DATA TO PREDICT SUSPENDED SEDIMENT CONCENTRATIONS: POSSIBILITIES, LIMITATIONS, AND PITFALLS

Science.gov (United States)

This talk will look at the relationships between turbidity and suspended sediment concentrations in a variety of geographic areas, geomorphic river types, and river sizes; and attempt to give guidance on using existing turbidity data to predict suspended sediment concentrations.

Spatial dependence in wind and optimal wind power allocation: A copula-based analysis

International Nuclear Information System (INIS)

Grothe, Oliver; Schnieders, Julius

2011-01-01

The investment decision on the placement of wind turbines is, neglecting legal formalities, mainly driven by the aim to maximize the expected annual energy production of single turbines. The result is a concentration of wind farms at locations with high average wind speed. While this strategy may be optimal for single investors maximizing their own return on investment, the resulting overall allocation of wind turbines may be unfavorable for energy suppliers and the economy because of large fluctuations in the overall wind power output. This paper investigates to what extent optimal allocation of wind farms in Germany can reduce these fluctuations. We analyze stochastic dependencies of wind speed for a large data set of German on- and offshore weather stations and find that these dependencies turn out to be highly nonlinear but constant over time. Using copula theory we determine the value at risk of energy production for given allocation sets of wind farms and derive optimal allocation plans. We find that the optimized allocation of wind farms may substantially stabilize the overall wind energy supply on daily as well as hourly frequency. - Highlights: → Spatial modeling of wind forces in Germany. → A novel way to assess nonlinear dependencies of wind forces by copulas. → Wind turbine allocation by maximizing lower quantiles of energy production. → Optimal results show major increase in reliable part of wind energy.

Recovery of diverse microbes in high turbidity surface water samples using dead-end ultrafiltration.

Science.gov (United States)

Mull, Bonnie; Hill, Vincent R

2012-12-01

Dead-end ultrafiltration (DEUF) has been reported to be a simple, field-deployable technique for recovering bacteria, viruses, and parasites from large-volume water samples for water quality testing and waterborne disease investigations. While DEUF has been reported for application to water samples having relatively low turbidity, little information is available regarding recovery efficiencies for this technique when applied to sampling turbid water samples such as those commonly found in lakes and rivers. This study evaluated the effectiveness of a DEUF technique for recovering MS2 bacteriophage, enterococci, Escherichia coli, Clostridium perfringens, and Cryptosporidium parvum oocysts in surface water samples having elevated turbidity. Average recovery efficiencies for each study microbe across all turbidity ranges were: MS2 (66%), C. parvum (49%), enterococci (85%), E. coli (81%), and C. perfringens (63%). The recovery efficiencies for MS2 and C. perfringens exhibited an inversely proportional relationship with turbidity, however no significant differences in recovery were observed for C. parvum, enterococci, or E. coli. Although ultrafilter clogging was observed, the DEUF method was able to process 100-L surface water samples at each turbidity level within 60 min. This study supports the use of the DEUF method for recovering a wide array of microbes in large-volume surface water samples having medium to high turbidity. Published by Elsevier B.V.

Panorama 2013 - Offshore wind power

International Nuclear Information System (INIS)

Vinot, Simon

2012-10-01

While onshore wind power is already a well-developed global industry, offshore wind power is still in the consolidation and globalization phase. The most mature of marine renewable energies is beginning to venture off the European coast and even to other continents, driven by public policies and the ever increasing number of players joining this promising market, which should evolve into deeper waters thanks to floating structures. (author)

Nucleosynthesis in neutrino-driven winds: Influence of the nuclear physics input

International Nuclear Information System (INIS)

Arcones, Almudena; Martinez-Pinedo, Gabriel

2010-01-01

We have performed hydrodynamical simulations of the long-time evolution of proto-neutron stars to study the nucleosynthesis using the resulting wind trajectories. Although the conditions found in the present wind models are not favourable for the production of heavy elements, a small enhancement of the entropy results in the production of r-process elements with A ∼ 195. This allows us to explore the sensitivity of their production to the hydrodynamical evolution (wind termination shock) and nuclear physics input used.

Estuarine beaches of the Amazon coast: environmental and recreational characterization

OpenAIRE

de Sousa, Rosigleyse C.; Pereira, Luci Cajueiro Carneiro; Jiménez Quintana, José Antonio

2016-01-01

The Amazon coast is rich in natural resources, with highly valued natural landscapes and ecological systems. These environments include estuarine beaches, which are important areas for recreational activities. The present study provides an environmental and recreational diagnosis of three of these estuarine beaches on the Amazon coast (Colares, Maruda, and Murubira). The study was conducted in July, 2012, 2013 and 2015. An set of variables was assessed: (i) physical variables (hydrodynamics),...

EFFECTIVENESS OF CHITOSAN AS NATURAL COAGULANT AID IN TREATING TURBID WATERS

Directory of Open Access Journals (Sweden)

B. Bina ، M. H. Mehdinejad ، M. Nikaeen ، H. Movahedian Attar

2009-10-01

Full Text Available During the last decade, there has been a concern about the relation between aluminum residuals in treated water and Alzheimer disease, and more interest has been considered on the development of natural coagulants such as chitosan. Chitosan, a natural linear biopolyaminosaccharide, is obtained by alkaline deacetylation of chitin. The present study was aimed to investigate the effects of alum as coagulant in conjunction with chitosan as coagulant aid on the removal of turbidity, hardness and Escherichia coli from water. A conventional jar test apparatus was employed for the tests. The optimum pH was observed between 7 to 7.5 for all turbidities. The optimum doses of alum and chitosan when used in conjunction, were 10mg/L and 1mg/L, 5mg/L and 0.5mg/L, and 5mg/L and 0.5mg/L in low, medium and high turbidities, respectively. Turbidity removal efficiency was resulted between %74.3 to %98.2 by alum in conjunction with chitosan. Residual Al+3 in treated water was less than 0.2 mg/L, meeting the international guidelines. The results showed that turbidity decrease provided also a primary Escherichia coli reduction of 2-4 log units within the first 1 to 2 hr of treatment. Hardness removal efficiency decreased when the total hardness increased from 102 to 476mg/L as CaCO3. At low initial turbidity, chitosan showed marginally better performance on hardness, especially at the ranges of 100 to 210 mg/L as CaCO3. In conclusion, coagulant aid showed a useful method for coagulation process. By using natural coagulants, considerable savings in chemicals and sludge handling cost may be achieved.

Impact of wind on the spatial distribution of rain over micro-scale topography : numerical modelling and experimental verification

NARCIS (Netherlands)

Blocken, B.J.E.; Poesen, J.; Carmeliet, J.

2006-01-01

The wind-driven-rain effect refers to the redistribution of rainfall over micro-scale topography due to the existence of local perturbed wind-flow patterns. Rainfall measurements reported in the literature point to the fact that the wind-driven-rain distribution can show large variations over

Wind hazard assessment for Point Lepreau Generating Station

International Nuclear Information System (INIS)

Mullin, D.; Moland, M.; Sciaudone, J.C.; Twisdale, L.A.; Vickery, P.J.; Mizzen, D.R.

2015-01-01

In response to the CNSC Fukushima Action Plan, NB Power has embarked on a wind hazard assessment for the Point Lepreau Generating Station site that incorporates the latest up to date wind information and modeling. The objective was to provide characterization of the wind hazard from all potential sources and estimate wind-driven missile fragilities and wind pressure fragilities for various structures, systems and components that would provide input to a possible high wind Probabilistic Safety Assessment. The paper will discuss the overall methodology used to assess hazards related to tornadoes, hurricanes and straight-line winds, and site walk-down and hazard/fragility results. (author)

Influence of strong monsoon winds on the water quality around a marine cage-culture zone in a shallow and semi-enclosed bay in Taiwan.

Science.gov (United States)

Huang, Yuan-Chao Angelo; Huang, Shou-Chung; Meng, Pei-Jie; Hsieh, Hernyi Justin; Chen, Chaolun Allen

2012-04-01

Influences of marine cage culture and monsoonal disturbances, northeasterly (NE) and southwesterly (SW) monsoons on the proximal marine environment were investigated across a gradient of sites in a semi-enclosed bay, Magong Bay (Penghu Islands, Taiwan). Elevated levels of ammonia produced by the cages were the main pollutant and distinguished the cage-culture and intermediary zones (1000 m away from the cages) from the reference zone in the NE monsoon, indicating currents produced by the strong monsoon may have extended the spread of nutrient-enriched waters without necessarily flushing such effluents outside Magong Bay. Moreover, the levels of chlorophyll-a, dissolved oxygen, and turbidity were distinguishable between two seasons, suggesting that resuspension caused by the NE monsoon winds may also influence the water quality across this bay. It indicated that the impacts of marine cage culture vary as a function of distance, and also in response to seasonal movements of water driven by local climatic occurrences. Copyright © 2012 Elsevier Ltd. All rights reserved.

AGN feedback through UFO and galaxy-wide winds in the early Universe

Science.gov (United States)

Feruglio, C.; Piconcelli, E.; Bischetti, M.; Zappacosta, L.; Fiore, F.

2017-10-01

AGN feedback through massive molecular winds is today routinely observed in local AGN host galaxies, but not as such in the early universe. I will present the first evidence for a massive, AGN-driven molecular wind in the z 4 QSO APM08279, which also hosts the most well studied and persistent nuclear semi-raltivistic wind (UFO). This observation directly probes the expansion mechanism of a nuclear wind into the ISM on galaxy wide scales, that so far was constrained by a couple of other objects only (Feruglio et al. 2015, Tombesi et al. 2015). This result also opens the path toward the exploration of molecular AGN-driven winds at early epochs, close after the end of the Epoch of Reionisation (EoR).

Turbidity forecasting at a karst spring using combined machine learning and wavelet multiresolution analysis.

Science.gov (United States)

Savary, M.; Massei, N.; Johannet, A.; Dupont, J. P.; Hauchard, E.

2016-12-01

25% of the world populations drink water extracted from karst aquifer. The comprehension and the protection of these aquifers appear as crucial due to an increase of drinking water needs. In Normandie(North-West of France), the principal exploited aquifer is the chalk aquifer. The chalk aquifer highly karstified is an important water resource, regionally speaking. Connections between surface and underground waters thanks to karstification imply turbidity that decreases water quality. Both numerous parameters and phenomenons, and the non-linearity of the rainfall/turbidity relation influence the turbidity causing difficulties to model and forecast turbidity peaks. In this context, the Yport pumping well provides half of Le Havreconurbation drinking water supply (236 000 inhabitants). The aim of this work is thus to perform prediction of the turbidity peaks in order to help pumping well managers to decrease the impact of turbidity on water treatment. Database consists in hourly rainfalls coming from six rain gauges located on the alimentation basin since 2009 and hourly turbidity since 1993. Because of the lack of accurate physical description of the karst system and its surface basin, the systemic paradigm is chosen and a black box model: a neural network model is chosen. In a first step, correlation analyses are used to design the original model architecture by identifying the relation between output and input. The following optimization phases bring us four different architectures. These models were experimented to forecast 12h ahead turbidity and threshold surpassing. The first model is a simple multilayer perceptron. The second is a two-branches model designed to better represent the fast (rainfall) and low (evapotranspiration) dynamics. Each kind of model is developed using both a recurrent and feed-forward architecture. This work highlights that feed-forward multilayer perceptron is better to predict turbidity peaks when feed-forward two-branches model is

Studies on growth and age of bivalves from temperate and tropical estuarine ecosystems

Digital Repository Service at National Institute of Oceanography (India)

Parulekar, A.H.

Comparison of growth progression and age composition of Abra alba and Nuculana minuta from temperate estuarine ecosystem with Meretrix casta and Paphia malabarica from tropical estuarine environment, revealed that the annual growth rate in tropical...

DRINKING WATER TURBIDITY AND EMERGENCY DEPARTMENT VISITS FOR GASTROINTESTINAL ILLNESS IN ATLANTA, 1993 – 2004

Science.gov (United States)

Tinker, Sarah C.; Moe, Christine L.; Klein, Mitchel; Flanders, W. Dana; Uber, Jim; Amirtharajah, Appiah; Singer, Philip; Tolbert, Paige E.

2013-01-01

Background The extent to which drinking water turbidity measurements indicate the risk of gastrointestinal illness is not well-understood. Despite major advances in drinking water treatment and delivery, infectious disease can still be transmitted through drinking water in the U.S., and it is important to have reliable indicators of microbial water quality to inform public health decisions. The objective of our study was to assess the relationship between gastrointestinal illness, quantified through emergency department visits, and drinking water quality, quantified as raw water and filtered water turbidity measured at the treatment plant. Methods We examined the relationship between turbidity levels of raw and filtered surface water measured at eight major drinking water treatment plants in the metropolitan area of Atlanta, Georgia, and over 240 000 emergency department visits for gastrointestinal illness during 1993–2004 among the population served by these plants. We fit Poisson time-series statistical regression models that included turbidity in a 21-day distributed lag and that controlled for meteorological factors and long-term time trends. Results For filtered water turbidity, the results were consistent with no association with emergency department visits for gastrointestinal illness. We observed a modest association between raw water turbidity and emergency department visits for gastrointestinal illness. This association was not observed for all treatment plants in plant-specific analyses. Conclusions Our results suggest that source water quality may contribute modestly to endemic gastrointestinal illness in the study area. The association between turbidity and emergency department visits for gastrointestinal illness was only observed when raw water turbidity was considered; filtered water turbidity may not serve as a reliable indicator of modest pathogen risk at all treatment plants. PMID:18941478

Potential of turbidity monitoring for real time control of pollutant discharge in sewers during rainfall events

OpenAIRE

LACOUR, Céline; JOANNIS, Claude; GROMAIRE, MC; CHEBBO, Ghassan

2009-01-01

Turbidity sensors can be used to continuously monitor the evolution of pollutant mass discharge. For two sites within the Paris combined sewer system, continuous turbidity, conductivity and flow data were recorded at one-minute time intervals over a one-year period. This paper is intended to highlight the variability in turbidity dynamics during wet weather. For each storm event, turbidity response aspects were analysed through different classifications. The correlation between classification...

Use of Three-Level Power Converters in Wind-Driven Permanent-Magnet Synchronous Generators with Unbalanced Loads

Directory of Open Access Journals (Sweden)

Ming-Hung Chen

2015-06-01

Full Text Available This paper describes the design and implementation of three-level power converters for wind-driven permanent-magnet synchronous generators with unbalanced loads. To increase voltage stress and reduce current harmonics in the electrical power generated by a wind generator, a three-phase, three-level rectifier is used. Because a synchronous rotating frame is used on the AC-input side, the use of a neutral-point-clamped controller is proposed to increase the power factor to unity and reduce current harmonics. Furthermore, a novel six-leg inverter is proposed for transferring energy from the DC voltage to a three-phase, four-wire AC source with a constant voltage and a constant frequency. The power converters also contain output transformers and filters for power buffering and filtering, respectively. All three output phase voltages are fed back to control the inverter output during load variations. A digital signal processor is used as the core control device for implementing a 1.5 kV, 75 kW drive system. Experimental data show that the power factor is successfully increased to unity and the total current harmonic distortion is 3.2% on the AC-input side. The entire system can attain an efficiency of 91%, and the voltage error between the upper and lower capacitors is approximately zero. Experimental results that confirm the high performance of the proposed system are presented.

Minimal incorporation of Deepwater Horizon oil by estuarine filter feeders

International Nuclear Information System (INIS)

Fry, Brian; Anderson, Laurie C.

2014-01-01

Highlights: • Oil from the Deepwater Horizon oil spill entered Louisiana bays in mid-2010. • Oil was used minimally (<1%) in diets of mussels and barnacles. • Also, oil did not enhance planktonic respiration rates. • Use of oil carbon was relatively small in these productive estuarine food webs. - Abstract: Natural abundance carbon isotope analyses are sensitive tracers for fates and use of oil in aquatic environments. Use of oil carbon in estuarine food webs should lead to isotope values approaching those of oil itself, −27‰ for stable carbon isotopes reflecting oil origins and −1000‰ for carbon-14 reflecting oil age. To test for transfer of oil from the 2010 Deepwater Horizon spill into estuarine food webs, filter-feeding barnacles (Balanus sp.) and marsh mussels (Geukensia demissa) were collected from Louisiana estuaries near the site of the oil spill. Carbon-14 analyses of these animals from open waters and oiled marshes showed that oil use was <1% and near detection limits estimated at 0.3% oil incorporation. Respiration studies showed no evidence for enhanced microbial activity in bay waters. Results are consistent with low dietary impacts of oil for filter feeders and little overall impact on respiration in the productive Louisiana estuarine systems

GoM Coastal and Estuarine Biopsy Surveys

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Small vessel surveys are conducted within estuarine and nearshore coastal waters to collect tissue biopsy samples from bottlenose dolphins. Visual surveys are...

Wind gust measurements using pulsed Doppler wind-lidar: comparison of direct and indirect techniques

DEFF Research Database (Denmark)

The measurements of wind gusts, defined as short duration wind speed maxima, have traditionally been limited by the height that can be reached by weather masts. Doppler lidars can potentially provide information from levels above this and thereby fill this gap in our knowledge. To measure the 3D...... is 3.9 s) which can provide high resolution turbulent measurements, both in the vertical direction, and potentially in the horizontal direction. In this study we explore different strategies of wind lidar measurements to measure the wind speed maxima. We use a novel stochastic turbulence reconstruction...... model, driven by the Doppler lidar measurements, which uses a non-linear particle filter to estimate the small-scale turbulent fluctuations. The first results show that the reconstruction method can reproduce the wind speed maxima measured by the sonic anemometer if a low-pass filter with a cut...

A user's guide to coping with estuarine management bureaucracy: An Estuarine Planning Support System (EPSS) tool.

Science.gov (United States)

Lonsdale, Jemma; Nicholson, Rose; Weston, Keith; Elliott, Michael; Birchenough, Andrew; Sühring, Roxana

2018-02-01

Estuaries are amongst the most socio-economically and ecologically important environments however, due to competing and conflicting demands, management is often challenging with a complex legislative framework managed by multiple agencies. To facilitate the understanding of this legislative framework, we have developed a GISbased Estuarine Planning Support System tool. The tool integrates the requirements of the relevant legislation and provides a basis for assessing the current environmental state of an estuary as well as informing and assessing new plans to ensure a healthy estuarine state. The tool ensures that the information is easily accessible for regulators, managers, developers and the public. The tool is intended to be adaptable, but is assessed using the Humber Estuary, United Kingdom as a case study area. The successful application of the tool for complex socio-economic and environmental systems demonstrates that the tool can efficiently guide users through the complex requirements needed to support sustainable development. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

Modeling of Turbidity Variation in Two Reservoirs Connected by a Water Transfer Tunnel in South Korea

Directory of Open Access Journals (Sweden)

Jae Chung Park

2017-06-01

Full Text Available The Andong and Imha reservoirs in South Korea are connected by a water transfer tunnel. The turbidity of the Imha reservoir is much higher than that of the Andong reservoir. Thus, it is necessary to examine the movement of turbidity between the two reservoirs via the water transfer tunnel. The aim of this study was to investigate the effect of the water transfer tunnel on the turbidity behavior of the two connecting reservoirs and to further understand the effect of reservoir turbidity distribution as a function of the selective withdrawal depth. This study applied the CE-QUAL-W2, a water quality and 2-dimensional hydrodynamic model, for simulating the hydrodynamic processes of the two reservoirs. Results indicate that, in the Andong reservoir, the turbidity of the released water with the water transfer tunnel was similar to that without the tunnel. However, in the Imha reservoir, the turbidity of the released water with the water transfer tunnel was lower than that without the tunnel. This can be attributed to the higher capacity of the Andong reservoir, which has double the storage of the Imha reservoir. Withdrawal turbidity in the Imha reservoir was investigated using the water transfer tunnel. This study applied three withdrawal selections as elevation (EL. 141.0 m, 146.5 m, and 152.0 m. The highest withdrawal turbidity resulted in EL. 141.0 m, which indicates that the high turbidity current is located at a vertical depth of about 20–30 m because of the density difference. These results will be helpful for understanding the release and selective withdrawal turbidity behaviors for a water transfer tunnel between two reservoirs.

Drinking water turbidity and emergency department visits for gastrointestinal illness in New York City, 2002-2009.

Directory of Open Access Journals (Sweden)

Jennifer L Hsieh

Full Text Available Studies have examined whether there is a relationship between drinking water turbidity and gastrointestinal (GI illness indicators, and results have varied possibly due to differences in methods and study settings.As part of a water security improvement project we conducted a retrospective analysis of the relationship between drinking water turbidity and GI illness in New York City (NYC based on emergency department chief complaint syndromic data that are available in near-real-time.We used a Poisson time-series model to estimate the relationship of turbidity measured at distribution system and source water sites to diarrhea emergency department (ED visits in NYC during 2002-2009. The analysis assessed age groups and was stratified by season and adjusted for sub-seasonal temporal trends, year-to-year variation, ambient temperature, day-of-week, and holidays.Seasonal variation unrelated to turbidity dominated (~90% deviance the variation of daily diarrhea ED visits, with an additional 0.4% deviance explained with turbidity. Small yet significant multi-day lagged associations were found between NYC turbidity and diarrhea ED visits in the spring only, with approximately 5% excess risk per inter-quartile-range of NYC turbidity peaking at a 6 day lag. This association was strongest among those aged 0-4 years and was explained by the variation in source water turbidity.Integrated analysis of turbidity and syndromic surveillance data, as part of overall drinking water surveillance, may be useful for enhanced situational awareness of possible risk factors that can contribute to GI illness. Elucidating the causes of turbidity-GI illness associations including seasonal and regional variations would be necessary to further inform surveillance needs.

Drinking water turbidity and emergency department visits for gastrointestinal illness in New York City, 2002-2009.

Science.gov (United States)

Hsieh, Jennifer L; Nguyen, Trang Quyen; Matte, Thomas; Ito, Kazuhiko

2015-01-01

Studies have examined whether there is a relationship between drinking water turbidity and gastrointestinal (GI) illness indicators, and results have varied possibly due to differences in methods and study settings. As part of a water security improvement project we conducted a retrospective analysis of the relationship between drinking water turbidity and GI illness in New York City (NYC) based on emergency department chief complaint syndromic data that are available in near-real-time. We used a Poisson time-series model to estimate the relationship of turbidity measured at distribution system and source water sites to diarrhea emergency department (ED) visits in NYC during 2002-2009. The analysis assessed age groups and was stratified by season and adjusted for sub-seasonal temporal trends, year-to-year variation, ambient temperature, day-of-week, and holidays. Seasonal variation unrelated to turbidity dominated (~90% deviance) the variation of daily diarrhea ED visits, with an additional 0.4% deviance explained with turbidity. Small yet significant multi-day lagged associations were found between NYC turbidity and diarrhea ED visits in the spring only, with approximately 5% excess risk per inter-quartile-range of NYC turbidity peaking at a 6 day lag. This association was strongest among those aged 0-4 years and was explained by the variation in source water turbidity. Integrated analysis of turbidity and syndromic surveillance data, as part of overall drinking water surveillance, may be useful for enhanced situational awareness of possible risk factors that can contribute to GI illness. Elucidating the causes of turbidity-GI illness associations including seasonal and regional variations would be necessary to further inform surveillance needs.