WorldWideScience

Sample records for modelling nutrient loads

  1. Ensemble modelling of nutrient loads and nutrient load partitioning in 17 European catchments

    Czech Academy of Sciences Publication Activity Database

    Hejzlar, Josef

    2009-01-01

    Roč. 11, č. 3 (2009), s. 572-583 ISSN 1464-0325 Grant - others:EC(XE) EVK1-2001-00062 Institutional research plan: CEZ:AV0Z60170517 Keywords : catchment modelling * phosphorus and nitrogen loss es * agriculture land * diffuse sources Subject RIV: DJ - Water Pollution ; Quality Impact factor: 2.225, year: 2009

  2. Time-scale Dependence of Response of an Estuarine Water Quality Model to Nutrient Loading

    Science.gov (United States)

    We describe calibration and evaluation of a water quality model being implemented for Narragansett Bay to quantify the response of concentrations of nutrients, phytoplankton chlorophyll a and dissolved oxygen in the Bay to loading rates of nutrients and other boundary conditions....

  3. Quantifying Groundwater Nutrient Discharge to a Large Glacial Lake using a Watershed Loading Model

    Science.gov (United States)

    Schilling, K. E.

    2015-12-01

    Groundwater discharge to a lake is an important, if often neglected, component to water and nutrient budgets. Point measurements of groundwater discharge into a lake are prone to error, so in this study of 15.57 km2 West Lake Okoboji, Iowa, a watershed-based groundwater loading model was developed. Located in northwest Iowa, West Lake Okoboji is considered one of Iowa's premier tourist destinations but is threatened by eutrophication. A network of 21 observation wells was installed in the watershed to evaluate groundwater recharge and quality under representative land cover types in a range of landscape positions. Our objective was to develop typical groundwater responses from various land cover-landscape associations for scaling up to unmonitored areas in the watershed. Results indicated substantial variation in groundwater recharge and quality in the 3847 ha watershed. Recharge was similar among land covers under vegetation but was much lower under urban pavement. Nitrate-nitrogen concentrations were highest under cropped fields and lowest under perennial grassland and golf courses, whereas dissolved phosphorus was highest under residential and urban areas, including an engineered bioswale. A groundwater load allocation model indicated 91% of the nitrate load was from cropped areas and 7% from residential areas. In contrast, P loads were more equally divided among cropped fields (43%), perennial grass (36%) and residential (19%) areas. Based on the mass of nitrate and P in the lake, groundwater accounts for 71% and 18% of the nutrient inputs, respectively.

  4. Nutrient and Coliform Loading (NCL)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This is a database of available fecal coliform bacteria, fecal streptococci bacteria, and nutrient loading data. Loading for contaminants other than fecal coliform...

  5. Nonlinear regression modeling of nutrient loads in streams: A Bayesian approach

    Science.gov (United States)

    Qian, S.S.; Reckhow, K.H.; Zhai, J.; McMahon, G.

    2005-01-01

    A Bayesian nonlinear regression modeling method is introduced and compared with the least squares method for modeling nutrient loads in stream networks. The objective of the study is to better model spatial correlation in river basin hydrology and land use for improving the model as a forecasting tool. The Bayesian modeling approach is introduced in three steps, each with a more complicated model and data error structure. The approach is illustrated using a data set from three large river basins in eastern North Carolina. Results indicate that the Bayesian model better accounts for model and data uncertainties than does the conventional least squares approach. Applications of the Bayesian models for ambient water quality standards compliance and TMDL assessment are discussed. Copyright 2005 by the American Geophysical Union.

  6. Modeling spring-summer phytoplankton bloom in Lake Michigan with and without riverine nutrient loading

    Science.gov (United States)

    Luo, Lin; Wang, Jia; Hunter, Timothy; Wang, Dongxiao; Vanderploeg, Henry A.

    2017-11-01

    There were two phytoplankton blooms captured by remote sensing in Lake Michigan in 1998, one from March to May, and one during June. In this paper, those phytoplankton blooms were simulated by a coupled physical-biological model, driven by observed meteorological forcing in 1998. The model reasonably reproduced the lake currents. The biological model results, with and without riverine nutrient loading, were compared with the remote sensing data. A 3-month-long donut-like phytoplankton bloom that appeared in southern Lake Michigan was reasonably well simulated only when riverine input was included, indicating the importance of riverine nutrient input for supporting the growth of phytoplankton in Lake Michigan. The model with riverine input also captured a second event-driven phytoplankton bloom during June with weaker magnitude that occurred in mid-south Lake Michigan, which lasted for about 20 days. The major reason for the weaker bloom in June was that vertical mixing in the hydrodynamic model was too weak (leading to a mixed-layer depth of 20 m) to bring the bottom nutrient-rich water up to the epilimnion. High chlorophyll concentration that persisted in Green Bay for almost a year was simulated with less intensity.

  7. 78 FR 13874 - Watershed Modeling To Assess the Sensitivity of Streamflow, Nutrient, and Sediment Loads to...

    Science.gov (United States)

    2013-03-01

    ... characterize the sensitivity of streamflow, nutrient (nitrogen and phosphorus), and sediment loading to a range... (nitrogen and phosphorus) loading, and sediment loading to a range of plausible mid-21st century climate... Docket is located in the EPA Headquarters Docket Center, EPA West Building, Room 3334, 1301 Constitution...

  8. Bayesian modeling of the assimilative capacity component of nutrient total maximum daily loads

    Science.gov (United States)

    Faulkner, B. R.

    2008-08-01

    Implementing stream restoration techniques and best management practices to reduce nonpoint source nutrients implies enhancement of the assimilative capacity for the stream system. In this paper, a Bayesian method for evaluating this component of a total maximum daily load (TMDL) load capacity is developed and applied. The joint distribution of nutrient retention metrics from a literature review of 495 measurements was used for Monte Carlo sampling with a process transfer function for nutrient attenuation. Using the resulting histograms of nutrient retention, reference prior distributions were developed for sites in which some of the metrics contributing to the transfer function were measured. Contributing metrics for the prior include stream discharge, cross-sectional area, fraction of storage volume to free stream volume, denitrification rate constant, storage zone mass transfer rate, dispersion coefficient, and others. Confidence of compliance (CC) that any given level of nutrient retention has been achieved is also determined using this approach. The shape of the CC curve is dependent on the metrics measured and serves in part as a measure of the information provided by the metrics to predict nutrient retention. It is also a direct measurement, with a margin of safety, of the fraction of export load that can be reduced through changing retention metrics. For an impaired stream in western Oklahoma, a combination of prior information and measurement of nutrient attenuation was used to illustrate the proposed approach. This method may be considered for TMDL implementation.

  9. Factors affecting stream nutrient loads: A synthesis of regional SPARROW model results for the continental United States

    Science.gov (United States)

    Preston, Stephen D.; Alexander, Richard B.; Schwarz, Gregory E.; Crawford, Charles G.

    2011-01-01

    We compared the results of 12 recently calibrated regional SPARROW (SPAtially Referenced Regressions On Watershed attributes) models covering most of the continental United States to evaluate the consistency and regional differences in factors affecting stream nutrient loads. The models - 6 for total nitrogen and 6 for total phosphorus - all provide similar levels of prediction accuracy, but those for major river basins in the eastern half of the country were somewhat more accurate. The models simulate long-term mean annual stream nutrient loads as a function of a wide range of known sources and climatic (precipitation, temperature), landscape (e.g., soils, geology), and aquatic factors affecting nutrient fate and transport. The results confirm the dominant effects of urban and agricultural sources on stream nutrient loads nationally and regionally, but reveal considerable spatial variability in the specific types of sources that control water quality. These include regional differences in the relative importance of different types of urban (municipal and industrial point vs. diffuse urban runoff) and agriculture (crop cultivation vs. animal waste) sources, as well as the effects of atmospheric deposition, mining, and background (e.g., soil phosphorus) sources on stream nutrients. Overall, we found that the SPARROW model results provide a consistent set of information for identifying the major sources and environmental factors affecting nutrient fate and transport in United States watersheds at regional and subregional scales. ?? 2011 American Water Resources Association. This article is a U.S. Government work and is in the public domain in the USA.

  10. Internal cycling, not external loading, decides the nutrient limitation in eutrophic lake: A dynamic model with temporal Bayesian hierarchical inference.

    Science.gov (United States)

    Wu, Zhen; Liu, Yong; Liang, Zhongyao; Wu, Sifeng; Guo, Huaicheng

    2017-06-01

    Lake eutrophication is associated with excessive anthropogenic nutrients (mainly nitrogen (N) and phosphorus (P)) and unobserved internal nutrient cycling. Despite the advances in understanding the role of external loadings, the contribution of internal nutrient cycling is still an open question. A dynamic mass-balance model was developed to simulate and measure the contributions of internal cycling and external loading. It was based on the temporal Bayesian Hierarchical Framework (BHM), where we explored the seasonal patterns in the dynamics of nutrient cycling processes and the limitation of N and P on phytoplankton growth in hyper-eutrophic Lake Dianchi, China. The dynamic patterns of the five state variables (Chla, TP, ammonia, nitrate and organic N) were simulated based on the model. Five parameters (algae growth rate, sediment exchange rate of N and P, nitrification rate and denitrification rate) were estimated based on BHM. The model provided a good fit to observations. Our model results highlighted the role of internal cycling of N and P in Lake Dianchi. The internal cycling processes contributed more than external loading to the N and P changes in the water column. Further insights into the nutrient limitation analysis indicated that the sediment exchange of P determined the P limitation. Allowing for the contribution of denitrification to N removal, N was the more limiting nutrient in most of the time, however, P was the more important nutrient for eutrophication management. For Lake Dianchi, it would not be possible to recover solely by reducing the external watershed nutrient load; the mechanisms of internal cycling should also be considered as an approach to inhibit the release of sediments and to enhance denitrification. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Estimating summer nutrient concentrations in Northeastern lakes from SPARROW load predictions and modeled lake depth and volume.

    Directory of Open Access Journals (Sweden)

    W Bryan Milstead

    Full Text Available Global nutrient cycles have been altered by the use of fossil fuels and fertilizers resulting in increases in nutrient loads to aquatic systems. In the United States, excess nutrients have been repeatedly reported as the primary cause of lake water quality impairments. Setting nutrient criteria that are protective of a lakes ecological condition is one common solution; however, the data required to do this are not always easily available. A useful solution for this is to combine available field data (i.e., The United States Environmental Protection Agency (USEPA National Lake Assessment (NLA with average annual nutrient load models (i.e., USGS SPARROW model to estimate summer concentrations across a large number of lakes. In this paper we use this combined approach and compare the observed total nitrogen (TN and total phosphorus (TN concentrations in Northeastern lakes from the 2007 National Lake Assessment to those predicted by the Northeast SPARROW model. We successfully adjusted the SPARROW predictions to the NLA observations with the use of Vollenweider equations, simple input-output models that predict nutrient concentrations in lakes based on nutrient loads and hydraulic residence time. This allows us to better predict summer concentrations of TN and TP in Northeastern lakes and ponds. On average we improved our predicted concentrations of TN and TP with Vollenweider models by 18.7% for nitrogen and 19.0% for phosphorus. These improved predictions are being used in other studies to model ecosystem services (e.g., aesthetics and dis-services (e.g. cyanobacterial blooms for ~18,000 lakes in the Northeastern United States.

  12. Modelling the effect of climate change on nutrient loading, temperature regime and algal biomass in the Gulf of Finland

    Energy Technology Data Exchange (ETDEWEB)

    Inkala, A. [Environmental Impact Assessment Center of Finland, Espoo (Finland); Bilaletdin, Ae.; Podsetchine, V. [Regional Environmental Agency of Haeme, Tampere (Finland)

    1997-12-31

    Climate changes and the potential related warming can change runoff, nutrient transport, mean wind velocities and water temperatures. These changes will further effect algal growth in a way that can be modelled. The changes to the nutrient load, temperature regime and algal biomass were simulated by three separate models. The simulations were made for the years 2020, 2050 and 2090. The simulated temperature variations and nutrient loading dynamics were used by algal model to predict changes of the algal biomass under the three different climate scenarios. According to the different scenarios, the maximum temperature of the surface water increased by 0.3-6.2 deg C, but in the deeper waters (> 40 m) by less than 0.1 deg C. The major part of the nutrient loads is anthropologic and this part did not change in the scenarios. Thus the changes in the algal biomass were also relatively small. However, the timing and quantity of spring bloom did change noticeably, at most in 2090, two weeks earlier and 20 % higher than nowadays. (orig.)

  13. Data to support statistical modeling of instream nutrient load based on watershed attributes, southeastern United States, 2002

    Science.gov (United States)

    Hoos, Anne B.; Terziotti, Silvia; McMahon, Gerard; Savvas, Katerina; Tighe, Kirsten C.; Alkons-Wolinsky, Ruth

    2008-01-01

    This report presents and describes the digital datasets that characterize nutrient source inputs, environmental characteristics, and instream nutrient loads for the purpose of calibrating and applying a nutrient water-quality model for the southeastern United States for 2002. The model area includes all of the river basins draining to the south Atlantic and the eastern Gulf of Mexico, as well as the Tennessee River basin (referred to collectively as the SAGT area). The water-quality model SPARROW (SPAtially-Referenced Regression On Watershed attributes), developed by the U.S. Geological Survey, uses a regression equation to describe the relation between watershed attributes (predictors) and measured instream loads (response). Watershed attributes that are considered to describe nutrient input conditions and are tested in the SPARROW model for the SAGT area as source variables include atmospheric deposition, fertilizer application to farmland, manure from livestock production, permitted wastewater discharge, and land cover. Watershed and channel attributes that are considered to affect rates of nutrient transport from land to water and are tested in the SAGT SPARROW model as nutrient-transport variables include characteristics of soil, landform, climate, reach time of travel, and reservoir hydraulic loading. Datasets with estimates of each of these attributes for each individual reach or catchment in the reach-catchment network are presented in this report, along with descriptions of methods used to produce them. Measurements of nutrient water quality at stream monitoring sites from a combination of monitoring programs were used to develop observations of the response variable - mean annual nitrogen or phosphorus load - in the SPARROW regression equation. Instream load of nitrogen and phosphorus was estimated using bias-corrected log-linear regression models using the program Fluxmaster, which provides temporally detrended estimates of long-term mean load well

  14. Modelling the eutrophication of the Seine Bight (France) under historical, present and future riverine nutrient loading

    Science.gov (United States)

    Cugier, P.; Billen, G.; Guillaud, J. F.; Garnier, J.; Ménesguen, A.

    2005-03-01

    Because of the occurrence of episodic blooms of toxic dinoflagellates, eutrophication of the Seine Bight is a subject of growing concern. In order to better understand the relationships between these processes and human activity in the Seine watershed, two models have been used in connection: A model describing nutrient (N, P, Si) transfer processes at the scale of the whole Seine Basin (RIVERSTRAHLER [Billen, G., Garnier, J., Ficht, A., Cun, C., 2001. Modelling the response of water quality in the Seine River Estuary in response to human activity in the watershed over the last 50 years. Estuaries 24, 977-993]), allowing human activity (agricultural practices, waterscape management, urban wastewater management, etc.) to be related to fluxes delivered to the sea. A model of 3D hydrodynamic and ecological model of the Seine Bight (SiAM-3D/ELISE [Cugier, P., 1999. Modélisation du devenir à moyen terme dans l'eau et le sédiment des éléments majeurs (N, P, Si, O) rejetés par la Seine en baie de Seine. Thèse de doctorat, Univ. de Caen, p. 241; Cugier, P., Le Hir, P., 2000. Modélisation 3D des matières en suspension en baie de Seine Orientale (Manche, France). C. R. Acad. Sci. Paris, Sciences de la Terre et des planétes 331, 287-294]), capable of reproducing the spatio-temporal variations of sediment transport, thermo-haline stratification and phytoplanktonic development in the plume of the Seine river. The models are validated by their ability to reproduce observed trends of interannual variations of nutrients delivered by the Seine during the last 50 years, as well as the response of the marine system in terms of diatoms and dinoflagellate development, for which data are available from 1976 to 1984 for the former and from 1987 to 1997 for the latter. The results show clearly that dry years, where silica inputs show a deficit with respect to nitrogen and phosphorus, are those where summer blooms of dinoflagellates are particularly pronounced. Various scenarios

  15. Modeling transport of nutrients & sediment loads into Lake Tahoe under climate change

    Science.gov (United States)

    Riverson, John; Coats, Robert; Costa-Cabral, Mariza; Dettinger, Mike; Reuter, John; Sahoo, Goloka; Schladow, Geoffrey

    2013-01-01

    The outputs from two General Circulation Models (GCMs) with two emissions scenarios were downscaled and bias-corrected to develop regional climate change projections for the Tahoe Basin. For one model—the Geophysical Fluid Dynamics Laboratory or GFDL model—the daily model results were used to drive a distributed hydrologic model. The watershed model used an energy balance approach for computing evapotranspiration and snowpack dynamics so that the processes remain a function of the climate change projections. For this study, all other aspects of the model (i.e. land use distribution, routing configuration, and parameterization) were held constant to isolate impacts of climate change projections. The results indicate that (1) precipitation falling as rain rather than snow will increase, starting at the current mean snowline, and moving towards higher elevations over time; (2) annual accumulated snowpack will be reduced; (3) snowpack accumulation will start later; and (4) snowmelt will start earlier in the year. Certain changes were masked (or counter-balanced) when summarized as basin-wide averages; however, spatial evaluation added notable resolution. While rainfall runoff increased at higher elevations, a drop in total precipitation volume decreased runoff and fine sediment load from the lower elevation meadow areas and also decreased baseflow and nitrogen loads basin-wide. This finding also highlights the important role that the meadow areas could play as high-flow buffers under climatic change. Because the watershed model accounts for elevation change and variable meteorological patterns, it provided a robust platform for evaluating the impacts of projected climate change on hydrology and water quality.

  16. Nutrient load estimates for Manila Bay, Philippines using population data

    NARCIS (Netherlands)

    Sotto, Lara Patricia A; Beusen, Arthur H W; Villanoy, Cesar L.; Bouwman, Lex F.; Jacinto, Gil S.

    2015-01-01

    A major source of nutrient load to periodically hypoxic Manila Bay is the urban nutrient waste water flow from humans and industries to surface water. In Manila alone, the population density is as high as 19,137 people/km2. A model based on a global point source model by Morée et al. (2013) was used

  17. Rating curve estimation of nutrient loads in Iowa rivers

    Science.gov (United States)

    Stenback, G.A.; Crumpton, W.G.; Schilling, K.E.; Helmers, M.J.

    2011-01-01

    Accurate estimation of nutrient loads in rivers and streams is critical for many applications including determination of sources of nutrient loads in watersheds, evaluating long-term trends in loads, and estimating loading to downstream waterbodies. Since in many cases nutrient concentrations are measured on a weekly or monthly frequency, there is a need to estimate concentration and loads during periods when no data is available. The objectives of this study were to: (i) document the performance of a multiple regression model to predict loads of nitrate and total phosphorus (TP) in Iowa rivers and streams; (ii) determine whether there is any systematic bias in the load prediction estimates for nitrate and TP; and (iii) evaluate streamflow and concentration factors that could affect the load prediction efficiency. A commonly cited rating curve regression is utilized to estimate riverine nitrate and TP loads for rivers in Iowa with watershed areas ranging from 17.4 to over 34,600km2. Forty-nine nitrate and 44 TP datasets each comprising 5-22years of approximately weekly to monthly concentrations were examined. Three nitrate data sets had sample collection frequencies averaging about three samples per week. The accuracy and precision of annual and long term riverine load prediction was assessed by direct comparison of rating curve load predictions with observed daily loads. Significant positive bias of annual and long term nitrate loads was detected. Long term rating curve nitrate load predictions exceeded observed loads by 25% or more at 33% of the 49 measurement sites. No bias was found for TP load prediction although 15% of the 44 cases either underestimated or overestimate observed long-term loads by more than 25%. The rating curve was found to poorly characterize nitrate and phosphorus variation in some rivers. ?? 2010 .

  18. Relating watershed nutrient loads to satellite derived estuarine water quality

    Science.gov (United States)

    Lehrter, J. C.; Le, C.

    2015-12-01

    Nutrient enhanced phytoplankton production is a cause of degraded estuarine water quality. Yet, relationships between watershed nutrient loads and the spatial and temporal scales of phytoplankton blooms and subsequent water quality impairments remain unquantified for most systems. This is partially due to a lack of observations. In many systems, satellite remote sensing of water quality variables may be used to supplement limited field observations and improve understanding of linkages to nutrients. Here, we present the results from a field and satellite ocean color study that quantitatively links nutrients to variations in estuarine water quality endpoints. The study was conducted in Pensacola Bay, Florida, an estuary in the northern Gulf of Mexico that is impacted by watershed nutrients. We developed new empirical band ratio algorithms to retrieve phytoplankton biomass as chlorophyll a (chla), colored dissolved organic matter (CDOM), and suspended particulate matter (SPM) from the MEdium Resolution Imaging Spectrometer (MERIS). MERIS had suitable spatial resolution (300-m) for the scale of Pensacola Bay (area = 370 km2, mean depth = 3.4 m) and a spectral band centered at wavelength 709 nm that was used to minimize the effect of organic matter on chla retrieval. The algorithms were applied to daily MERIS remote sensing reflectance (level 2) data acquired from 2003 to 2011 to calculate nine-year time-series of mean monthly chla, CDOM, and SPM concentrations. The MERIS derived time-series were then analyzed for statistical relations with time-series of mean monthly river discharge and river loads of nitrogen, phosphorus, dissolved organic carbon, and SPM. Regression analyses revealed significant relationships between river loads and MERIS water quality variables. The simple regression models provide quantitative predictions about how much chla, CDOM, and SPM concentrations in Pensacola Bay will increase with increased river loading, which is necessary information

  19. Assessment of nutrient loadings of a large multipurpose prairie reservoir

    Science.gov (United States)

    Morales-Marín, L. A.; Wheater, H. S.; Lindenschmidt, K. E.

    2017-07-01

    The relatively low water flow velocities in reservoirs cause them to have high capacities for retaining sediments and pollutants, which can lead to a reduction in downstream nutrient loading. Hence, nutrients can progressively accumulate in reservoirs, resulting in the deterioration of aquatic ecosystems and water quality. Lake Diefenbaker (LD) is a large multipurpose reservoir, located on the South Saskatchewan River (SSR), that serves as a major source of freshwater in Saskatchewan, Canada. Over the past several years, changes in land use (e.g. expansion of urban areas and industrial developments) in the reservoir's catchment have heightened concerns about future water quality in the catchment and in the reservoir. Intensification of agricultural activities has led to an increase in augmented the application of manure and fertilizer for crops and pasture. Although previous research has attempted to quantify nutrient retention in LD, there is a knowledge gap related to the identification of major nutrient sources and quantification of nutrient export from the catchment at different spatial scales. Using the SPAtially Referenced Regression On Watershed (SPARROW) model, this gap has been addressed by assessing water quality regionally, and identifying spatial patterns of factors and processes that affect water quality in the LD catchment. Model results indicate that LD retains about 70% of the inflowing total nitrogen (TN) and 90% of the inflowing total phosphorus (TP) loads, of which fertilizer and manure applied to agricultural fields contribute the greatest proportion. The SPARROW model will be useful as a tool to guide the optimal implementation of nutrient management plans to reduce nutrient inputs to LD.

  20. Quantifying the combined effects of land use and climate changes on stream flow and nutrient loads: A modelling approach in the Odense Fjord catchment (Denmark).

    Science.gov (United States)

    Molina-Navarro, Eugenio; Andersen, Hans E; Nielsen, Anders; Thodsen, Hans; Trolle, Dennis

    2018-04-15

    Water pollution and water scarcity are among the main environmental challenges faced by the European Union, and multiple stressors compromise the integrity of water resources and ecosystems. Particularly in lowland areas of northern Europe, high population density, flood protection and, especially, intensive agriculture, are important drivers of water quality degradation. In addition, future climate and land use changes may interact, with uncertain consequences for water resources. Modelling approaches have become essential to address water issues and to evaluate ecosystem management. In this work, three multi-stressor future storylines combining climatic and socio-economic changes, defined at European level, have been downscaled for the Odense Fjord catchment (Denmark), giving three scenarios: High-Tech agriculture (HT), Agriculture for Nature (AN) and Market-Driven agriculture (MD). The impacts of these scenarios on water discharge and inorganic and organic nutrient loads to the streams have been simulated using the Soil and Water Assessment Tool (SWAT). The results revealed that the scenario-specific climate inputs were most important when simulating hydrology, increasing river discharge in the HT and MD scenarios (which followed the high emission 8.5 representative concentration pathway, RCP), while remaining stable in the AN scenario (RCP 4.5). Moreover, discharge was the main driver of changes in organic nutrients and inorganic phosphorus loads that consequently increased in a high emission scenario. Nevertheless, both land use (via inputs of fertilizer) and climate changes affected the nitrate transport. Different levels of fertilization yielded a decrease in the nitrate load in AN and an increase in MD. In HT, however, nitrate losses remained stable because the fertilization decrease was counteracted by a flow increase. Thus, our results suggest that N loads will ultimately depend on future land use and management in an interaction with climate changes, and

  1. Impact of discharge data uncertainty on nutrient load uncertainty

    Science.gov (United States)

    Westerberg, Ida; Gustavsson, Hanna; Sonesten, Lars

    2016-04-01

    Uncertainty in the rating-curve model of the stage-discharge relationship leads to uncertainty in discharge time series. These uncertainties in turn affect many other analyses based on discharge data, such as nutrient load estimations. It is important to understand how large the impact of discharge data uncertainty is on such analyses, since they are often used as the basis to take important environmental management decisions. In the Baltic Sea basin, nutrient load estimates from river mouths are a central information basis for managing and reducing eutrophication in the Baltic Sea. In this study we investigated rating curve uncertainty and its propagation to discharge data uncertainty and thereafter to uncertainty in the load of phosphorous and nitrogen for twelve Swedish river mouths. We estimated rating curve uncertainty using the Voting Point method, which accounts for random and epistemic errors in the stage-discharge relation and allows drawing multiple rating-curve realisations consistent with the total uncertainty. We sampled 40,000 rating curves, and for each sampled curve we calculated a discharge time series from 15-minute water level data for the period 2005-2014. Each discharge time series was then aggregated to daily scale and used to calculate the load of phosphorous and nitrogen from linearly interpolated monthly water samples, following the currently used methodology for load estimation. Finally the yearly load estimates were calculated and we thus obtained distributions with 40,000 load realisations per year - one for each rating curve. We analysed how the rating curve uncertainty propagated to the discharge time series at different temporal resolutions, and its impact on the yearly load estimates. Two shorter periods of daily water quality sampling around the spring flood peak allowed a comparison of load uncertainty magnitudes resulting from discharge data with those resulting from the monthly water quality sampling.

  2. Hardening fertilization and nutrient loading of conifer seedlings

    Science.gov (United States)

    R. Kasten Dumroese

    2003-01-01

    Continuing to fertilize bareroot and container seedlings during the hardening process (from cessation of height growth until lifting) can improve seedling viability. The process of fertilizing during hardening has many names, but in the last decade a new term, nutrient loading, has come into use. The process of nutrient loading seedlings leads to luxury consumption...

  3. Using a Hydrodynamic and Biogeochemical Model to Investigate the Effects of Nutrient Loading from a Wastewater Treatment Plant into Lake Michigan

    Science.gov (United States)

    Khazaei, B.; Bravo, H.; Bootsma, H.

    2017-12-01

    There is clear evidence that excessive nutrient, in particular phosphorus (P), loading into Lake Michigan has produced significant problems, such as algal blooms, hypoxia, and reduced water quality. Addressing those problems requires understanding the transport and fate of P in the lake. The dominance of mixing and dispersion processes on the P transport has been demonstrated, yet recent research has shown the remarkable influence of dreissenid mussels and Cladophora on water clarity and the P budget. Since mussels and Cladophora tend to concentrate near the coastlines, nearshore-offshore P exchange is of a big importance. In this research, a computer model was developed to simulate the P cycle by incorporating the biogeochemical processes relevant to the transport of P into a 3D high-resolution hydrodynamic model. The near-bottom biogeochemical model consists of three linked modules: Cladophora, mussel, and sediment storage modules. The model was applied to the Milwaukee Metropolitan Sewerage District South Shore Wastewater Treatment Plant, between June and October of 2013 and 2015, as a case study. The plant outfall introduces a point source of P into the study domain—the nearshore zone of Lake Michigan adjacent to Milwaukee County. The model was validated against field observations of water temperature, dissolved phosphorus (DP), particulate phosphorus (PP), Cladophora biomass, and P content. The model simulations showed reasonably good agreement with field measurements. Model results showed a) different temporal patterns in 2013 and 2015, b) a larger range of fluctuations in DP than that in PP, and c) that the effects of mussels and Cladophora could explain the differences in patterns and ranges. PP concentrations showed more frequent spikes of concentration in 2013 due to resuspension events during that year because of stronger winds. The model is being applied as a management tool to test scenarios of nutrient loading to determine effluent P limits for the

  4. Modeling the Sensitivity of Primary Production in Lake Michigan to Nutrient Loads with and without Dreissenid Mussels

    Science.gov (United States)

    Dreissenid (quagga) mussels became established in large numbers in Lake Michigan beginning around 2004. Since then, significant changes have been observed in Lake Michigan open-water chlorophyll and nutrient concentrations, and in primary production. We updated the LM3-Eutro mode...

  5. Impact of Climate Variability and Landscape Patterns on Water Budget and Nutrient Loads in a Peri-urban Watershed: A Coupled Analysis Using Process-based Hydrological Model and Landscape Indices.

    Science.gov (United States)

    Li, Chongwei; Zhang, Yajuan; Kharel, Gehendra; Zou, Chris B

    2018-06-01

    Nutrient discharge into peri-urban streams and reservoirs constitutes a significant pressure on environmental management, but quantitative assessment of non-point source pollution under climate variability in fast changing peri-urban watersheds is challenging. Soil and Water Assessment Tool (SWAT) was used to simulate water budget and nutrient loads for landscape patterns representing a 30-year progression of urbanization in a peri-urban watershed near Tianjin metropolis, China. A suite of landscape pattern indices was related to nitrogen (N) and phosphorous (P) loads under dry and wet climate using CANOCO redundancy analysis. The calibrated SWAT model was adequate to simulate runoff and nutrient loads for this peri-urban watershed, with Nash-Sutcliffe coefficient (NSE) and coefficient of determination (R 2 ) > 0.70 and percentage bias (PBIAS) between -7 and +18 for calibration and validation periods. With the progression of urbanization, forest remained the main "sink" landscape while cultivated and urban lands remained the main "source" landscapes with the role of orchard and grassland being uncertain and changing with time. Compared to 1984, the landscape use pattern in 2013 increased nutrient discharge by 10%. Nutrient loads modelled under wet climate were 3-4 times higher than that under dry climate for the same landscape pattern. Results indicate that climate change could impose a far greater impact on runoff and nutrient discharge in a peri-urban watershed than landscape pattern change.

  6. Nutrient load estimates for Manila Bay, Philippines using population data

    Science.gov (United States)

    Sotto, Lara Patricia A.; Beusen, Arthur H. W.; Villanoy, Cesar L.; Bouwman, Lex F.; Jacinto, Gil S.

    2015-06-01

    A major source of nutrient load to periodically hypoxic Manila Bay is the urban nutrient waste water flow from humans and industries to surface water. In Manila alone, the population density is as high as 19,137 people/km2. A model based on a global point source model by Morée et al. (2013) was used to estimate the contribution of the population to nitrogen and phosphorus emissions which was then used in a water transport model to estimate the nitrogen (N) and phosphorus (P) loads to Manila Bay. Seven scenarios for 2050 were tested, with varying degrees and amounts for extent of sewage treatment, and population growth rates were also included. In scenario 1, the sewage connection and treatment remains the same as 2010; in scenario 2, sewage connection is improved but the treatment is the same; in scenario 3, the sewage connection as well as treatment is improved (70% tertiary); and in scenario 4, a more realistic situation of 70% primary treatment achieved with 100% connection to pipes is tested. Scenarios 5, 6, and 7 have the same parameters as 1, 2, and 3 respectively, but with the population growth rate per province reduced to half of what was used in 1, 2, and 3. In all scenarios, a significant increase in N and P loads was observed (varying from 27% to 469% relative to 2010 values). This was found even in scenario 3 where 70% of the waste water undergoes tertiary treatment which removes 80% N and 90% P. However, the lowest increase in N and P load into the bay was achieved in scenarios 5 to 7 where population growth rate is reduced to half of 2010 values. The results suggest that aside from improving sewage treatment, the continued increase of the human population in Manila at current growth rates will be an important determinant of N and P load into Manila Bay.

  7. Nutrient Models Developments Using Runoff-Nutrient Relationships in an Agricultural Prairie Basin, Manitoba.

    Science.gov (United States)

    Mahmood, T. H.; Pomeroy, J. W.; Wheater, H. S.; Elliott, J. A.; Baulch, H. M.; Lindenschmidt, K. E.

    2015-12-01

    Nutrient export to streams and lakes from agricultural activities can result in significant deterioration of water quality and aquatic ecosystem health. In Western Canada, particular concerns arise for prairie agricultural systems, which are dominated by the effects of a cold climate. Insufficient attention has been given to understand the links between cold region watershed responses and nutrient concentration and a robust watershed-scale modeling framework is needed to simulate nutrient concentration and loads. Long-term, field observations of nutrient concentration-runoff relationships were used to develop nutrient concentration models for the Tobacco Creek Model Watershed (TCMW) which drains into the Red River basin. Field observations include streamflow concentrations of N and P at multiple scales from two headwater basins. Distinct nutrient concentration-runoff models for snowmelt, rain on snow (ROS) and rainfall runoff processes were developed from observed runoff-nutrient concentration relationships. Snowmelt runoff had a moderately positive correlation with particulate nutrient concentrations but no correlation with that of dissolved nutrients. ROS runoff had a weak relationship with both particulate and dissolved nutrient concentrations. Rainfall runoff had the strongest positive correlation with particulate nutrient concentrations but no association with that of dissolved nutrients. The modeling approach also identified a clear hysteretic behavior in the relationship between runoff and particulate nutrient concentration during the 2013 snowmelt runoff event at the basin outlet gauge. The models provide insight into the hydrological controls on nutrient export from cold regions watersheds and the strong effects of inter-annual climatic variability. Snowmelt runoff is a reliable exporter of large nutrient loads while nutrient export by rainfall runoff exceeded snowmelt runoff during hydrologically wet summers such as 2002, 2005, 2011 and 2013.

  8. Coupling global models for hydrology and nutrient loading to simulate nitrogen and phosphorus retention in surface water – description of IMAGE–GNM and analysis of performance

    NARCIS (Netherlands)

    Beusen, A.H.W.; van Beek, L.P.H.; Bouwman, Lex; Mogollon, J.M.; Middelburg, J.B.M.

    2015-01-01

    The Integrated Model to Assess the Global Environment–Global Nutrient Model (IMAGE–GNM) is a global distributed, spatially explicit model using hydrology as the basis for describing nitrogen (N) and phosphorus (P) delivery to surface water, transport and in-stream retention in rivers, lakes,

  9. Agricultural nutrient loadings to the freshwater environment: the role of climate change and socioeconomic change

    Science.gov (United States)

    Xie, Hua; Ringler, Claudia

    2017-10-01

    Human activities, in particular agricultural production, interfere with natural cycles of nutrient elements, nitrogen (N) and phosphorus (P), leading to growing concerns about water quality degradation related to excessive nutrient loadings. Increases in agricultural production in response to population growth and wealth generation further increase risks associated with nutrient pollution. This paper presents results from projections of nutrient exports from global agricultural crop and pasture systems to the water environment generated using a process-based modeling approach. Brazil, China, India and the United States account for more than half of estimated global N and P loadings in the base year. Each country boasts large agriculture centers where high calculated loading values are found. Rapid growth in global agricultural nutrient loadings is projected. Growth of agricultural pollution loading is fastest in the group of low-income developing countries and loading growth rates also vary substantially with climate change scenario. Counter measures need to be taken to address the environmental risks associated with the projected rapid increase of agricultural nutrient loadings.

  10. Anthropogenic Nutrient Loading in the Northeastern US 1920-2000

    Science.gov (United States)

    Hale, R. L.; Ng, M.; Brideau, J. M.; Hoover, J. H.; Thomas, B.

    2010-12-01

    Human activities have dramatically altered biogeochemical cycles on local to global scales. Altered fluxes of nutrients (nitrogen, phosphorus) to freshwater systems have been driven directly by human-mediated fluxes (e.g., industrial N fixation) and indirectly due to changes in land and water systems that alter rates of biogeochemical transformations and transport vectors for nutrients. The Northeastern United States as a region underwent many biophysical and political changes over the 20th century, making it an excellent case study for understanding human-biogeochemical relationships over time. From 1920 to 2000, this region experienced significant losses of agricultural land and increases in forest and urban land cover. Furthermore, major national and state legislation, including nuisance laws and the Clean Water Act, was passed during the 20th century to control pollution problems, and major technological advances in wastewater treatment were made. Our goals were to: 1) describe quantitative changes in the spatial patterns of water quality over time, 2) understand the proximate (e.g., changes in land use, new technology) and 3) ultimate (e.g., major demographic, economic, social shifts) drivers of those patterns. Using data from the historic Census of Agriculture, the National Atmospheric Deposition Program, and primary literature, we create a comprehensive time series database of anthropogenic N and P inputs to the Northeast terrestrial system. Inputs are estimated for each county at decadal time scales. Inputs included atmospheric deposition of nitrogen, fertilizer, manure, enhanced biological nitrogen fixation, and domestic waste. We used this database, in conjunction with data on land use, reservoirs, climate, and stream nutrient loads estimated from USGS NWIS to develop a modified export coefficient model for 26 watersheds in the Northeast. We then used this model to estimate nutrient loads at the decadal scale for all HUC 8 watersheds in our study region

  11. Optical changes in a eutrophic estuary during reduced nutrient loadings

    DEFF Research Database (Denmark)

    Pedersen, Troels Møller; Sand-Jensen, Kaj; Markager, Stiig

    2014-01-01

    Loss of water clarity is one of the consequences of coastal eutrophication. Efforts have therefore been made to reduce external nutrient loadings of coastal waters. This paper documents improvements to water clarity between 1985 and 2008–2009 at four stations in the microtidal estuary Roskilde...... Fjord and find significant relationships to freshwater nutrient loadings. The paper then investigates to which extent changes in phytoplankton biomass (chlorophyll a (Chl a)), non-algal particulate organic matter (POM*), and residual attenuation in the water (K b), respectively, can account...... to 74 % in 1985 to 78 to 85 % in 2008–2009. Overall, efforts to reduce nutrient loading and improve water clarity appeared to have had a larger impact on POM* than on Chl a and colored dissolved organic matter concentrations in the estuary, which can account for the decrease in the scatter...

  12. Organic fertilizer decomposition and nutrient loads in water reservoir ...

    African Journals Online (AJOL)

    Decomposition in aquatic ecosystems is controlled by various factors. The study investigated the trend of decomposition and the potential nutrients loaded in reservoir water. Analysis of water samples and organic fertilizer composition was according to APHA (1995) and Klute (1986) respectively. Reservoir water ...

  13. Nutrient loadings from urban catchments under climate change scenarios: case studies in Stockholm, Sweden.

    Science.gov (United States)

    Wu, Jiechen; Malmström, Maria E

    2015-06-15

    Anthropogenic nutrient emissions and associated eutrophication of urban lakes are a global problem. Future changes in temperature and precipitation may influence nutrient loadings in lake catchments. A coupling method, where the Generalized Watershed Loading Functions method was tested in combination with source quantification in a Substance Flow Analysis structure, was suggested to investigate diffuse nutrient sources and pathways and climate change effects on the loadings to streamflow in urban catchments. This method may, with an acceptable level of uncertainty, be applied to urban catchments for first-hand estimations of nutrient loadings in the projected future and to highlight the need for further study and monitoring. Five lake catchments in Stockholm, Sweden (Råcksta Träsk, Judarn, Trekanten, Långsjön and Laduviken) were employed as case studies and potential climate change effects were explored by comparing loading scenarios in two periods (2000-2009 and 2021-2030). For the selected cases, the dominant diffuse sources of nutrients to urban streamflow were found to be background atmospheric concentration and vehicular traffic. The major pathways of the nitrogen loading were suggested to be from both developed areas and natural areas in the control period, while phosphorus was indicated to be largely transported through surface runoff from natural areas. Furthermore, for nitrogen, a modest redistribution of loadings from surface runoff and stormwater between seasons and an increase in the annual loading were suggested for the projected future climate scenarios as compared to the control period. The model was, due to poor monitoring data availability, only able to set an upper limit to nutrient transport by groundwater both in the control period and the future scenarios. However, for nitrogen, groundwater appeared to be the pathway most sensitive to climate change, with a considerable increase and seasonal redistribution of loadings. For phosphorus

  14. Reducing Nutrient Loadings of Marine Waters

    DEFF Research Database (Denmark)

    Paaby, H.; Jensen, J. J.; Kristensen, P.

    1996-01-01

    Based upon contributions to a Scandinavian conference on Transport, Agriculture and the Environment in a Regional and National Development Perspective : Quantitative and Modelling Approaches organised by AKF, the Institute of Local Government Studies, Denmark, held on Bornholm, December 1993....

  15. Nutrient Loadings to Streams of the Continental United States from Municipal and Industrial Effluent.

    Science.gov (United States)

    Maupin, Molly A; Ivahnenko, Tamara

    2011-10-01

    Data from the United States Environmental Protection Agency Permit Compliance System national database were used to calculate annual total nitrogen (TN) and total phosphorus (TP) loads to surface waters from municipal and industrial facilities in six major regions of the United States for 1992, 1997, and 2002. Concentration and effluent flow data were examined for approximately 118,250 facilities in 45 states and the District of Columbia. Inconsistent and incomplete discharge locations, effluent flows, and effluent nutrient concentrations limited the use of these data for calculating nutrient loads. More concentrations were reported for major facilities, those discharging more than 1 million gallons per day, than for minor facilities, and more concentrations were reported for TP than for TN. Analytical methods to check and improve the quality of the Permit Compliance System data were used. Annual loads were calculated using "typical pollutant concentrations" to supplement missing concentrations based on the type and size of facilities. Annual nutrient loads for over 26,600 facilities were calculated for at least one of the three years. Sewage systems represented 74% of all TN loads and 58% of all TP loads. This work represents an initial set of data to develop a comprehensive and consistent national database of point-source nutrient loads. These loads can be used to inform a wide range of water-quality management, watershed modeling, and research efforts at multiple scales.

  16. Nutrient loadings to streams of the continental United States from municipal and industrial effluent?

    Science.gov (United States)

    Maupin, Molly A.; Ivahnenko, Tamara

    2011-01-01

    Data from the United States Environmental Protection Agency Permit Compliance System national database were used to calculate annual total nitrogen (TN) and total phosphorus (TP) loads to surface waters from municipal and industrial facilities in six major regions of the United States for 1992, 1997, and 2002. Concentration and effluent flow data were examined for approximately 118,250 facilities in 45 states and the District of Columbia. Inconsistent and incomplete discharge locations, effluent flows, and effluent nutrient concentrations limited the use of these data for calculating nutrient loads. More concentrations were reported for major facilities, those discharging more than 1 million gallons per day, than for minor facilities, and more concentrations were reported for TP than for TN. Analytical methods to check and improve the quality of the Permit Compliance System data were used. Annual loads were calculated using "typical pollutant concentrations" to supplement missing concentrations based on the type and size of facilities. Annual nutrient loads for over 26,600 facilities were calculated for at least one of the three years. Sewage systems represented 74% of all TN loads and 58% of all TP loads. This work represents an initial set of data to develop a comprehensive and consistent national database of point-source nutrient loads. These loads can be used to inform a wide range of water-quality management, watershed modeling, and research efforts at multiple scales.

  17. Effectiveness of submerged drains in reducing subsidence of peat soils in agricultural use, and their effects on water management and nutrient loading of surface water: modelling of a case study in the western peat soil area of The Netherlands

    Science.gov (United States)

    Hendriks, Rob F. A.; van den Akker, Jan J. A.

    2017-04-01

    Effectiveness of submerged drains in reducing subsidence of peat soils in agricultural use, and their effects on water management and nutrient loading of surface water: modelling of a case study in the western peat soil area of The Netherlands In the Netherlands, about 8% of the area is covered by peat soils. Most of these soils are in use for dairy farming and, consequently, are drained. Drainage causes decomposition of peat by oxidation and accordingly leads to surface subsidence and greenhouse gas emission. Submerged drains that enhance submerged infiltration of water from ditches during the dry and warm summer half year were, and are still, studied in The Netherlands as a promising tool for reducing peat decomposition by raising groundwater levels. For this purpose, several pilot field studies in the Western part of the Dutch peat area were conducted. Besides the effectiveness of submerged drains in reducing peat decomposition and subsidence by raising groundwater tables, some other relevant or expected effects of these drains were studied. Most important of these are water management and loading of surface water with nutrients nitrogen, phosphorus and sulphate. Because most of these parameters are not easy to assess and all of them are strongly depending on the meteorological conditions during the field studies some of these studies were modelled. The SWAP model was used for evaluating the hydrological results on groundwater table and water discharge and recharge. Effects of submerged drains were assessed by comparing the results of fields with and without drains. An empirical relation between deepest groundwater table and subsidence was used to convert effects on groundwater table to effects on subsidence. With the SWAP-ANIMO model nutrient loading of surface water was modelled on the basis of field results on nutrient concentrations . Calibrated models were used to assess effects in the present situation, as thirty-year averages, under extreme weather

  18. Effects of changes in nutrient loading and composition on hypoxia dynamics and internal nutrient cycling of a stratified coastal lagoon

    Science.gov (United States)

    Zhu, Yafei; McCowan, Andrew; Cook, Perran L. M.

    2017-10-01

    The effects of changes in catchment nutrient loading and composition on the phytoplankton dynamics, development of hypoxia and internal nutrient dynamics in a stratified coastal lagoon system (the Gippsland Lakes) were investigated using a 3-D coupled hydrodynamic biogeochemical water quality model. The study showed that primary production was equally sensitive to changed dissolved inorganic and particulate organic nitrogen loads, highlighting the need for a better understanding of particulate organic matter bioavailability. Stratification and sediment carbon enrichment were the main drivers for the hypoxia and subsequent sediment phosphorus release in Lake King. High primary production stimulated by large nitrogen loading brought on by a winter flood contributed almost all the sediment carbon deposition (as opposed to catchment loads), which was ultimately responsible for summer bottom-water hypoxia. Interestingly, internal recycling of phosphorus was more sensitive to changed nitrogen loads than total phosphorus loads, highlighting the potential importance of nitrogen loads exerting a control over systems that become phosphorus limited (such as during summer nitrogen-fixing blooms of cyanobacteria). Therefore, the current study highlighted the need to reduce both total nitrogen and total phosphorus for water quality improvement in estuarine systems.

  19. Effects of changes in nutrient loading and composition on hypoxia dynamics and internal nutrient cycling of a stratified coastal lagoon

    Directory of Open Access Journals (Sweden)

    Y. Zhu

    2017-10-01

    Full Text Available The effects of changes in catchment nutrient loading and composition on the phytoplankton dynamics, development of hypoxia and internal nutrient dynamics in a stratified coastal lagoon system (the Gippsland Lakes were investigated using a 3-D coupled hydrodynamic biogeochemical water quality model. The study showed that primary production was equally sensitive to changed dissolved inorganic and particulate organic nitrogen loads, highlighting the need for a better understanding of particulate organic matter bioavailability. Stratification and sediment carbon enrichment were the main drivers for the hypoxia and subsequent sediment phosphorus release in Lake King. High primary production stimulated by large nitrogen loading brought on by a winter flood contributed almost all the sediment carbon deposition (as opposed to catchment loads, which was ultimately responsible for summer bottom-water hypoxia. Interestingly, internal recycling of phosphorus was more sensitive to changed nitrogen loads than total phosphorus loads, highlighting the potential importance of nitrogen loads exerting a control over systems that become phosphorus limited (such as during summer nitrogen-fixing blooms of cyanobacteria. Therefore, the current study highlighted the need to reduce both total nitrogen and total phosphorus for water quality improvement in estuarine systems.

  20. Patchiness in a minimal nutrient – phytoplankton model

    Indian Academy of Sciences (India)

    Srinivas

    increase in nutrient loading, which means the progress of eutrophication, makes the system converge to a stable equilibrium state. The return to homogeneous distribution means that adoption of the two-component model with nutrients and phytoplankton is one of the possible ways to avoid continuing limit-cycle oscillations ...

  1. Electrical load modeling

    Energy Technology Data Exchange (ETDEWEB)

    Valgas, Helio Moreira; Pinto, Roberto del Giudice R.; Franca, Carlos [Companhia Energetica de Minas Gerais (CEMIG), Belo Horizonte, MG (Brazil); Lambert-Torres, Germano; Silva, Alexandre P. Alves da; Pires, Robson Celso; Costa Junior, Roberto Affonso [Escola Federal de Engenharia de Itajuba, MG (Brazil)

    1994-12-31

    Accurate dynamic load models allow more precise calculations of power system controls and stability limits, which are critical mainly in the operation planning of power systems. This paper describes the development of a computer program (software) for static and dynamic load model studies using the measurement approach for the CEMIG system. Two dynamic load model structures are developed and tested. A procedure for applying a set of measured data from an on-line transient recording system to develop load models is described. (author) 6 refs., 17 figs.

  2. Submarine ground-water discharge: nutrient loading and nitrogen transformations

    Science.gov (United States)

    Kroeger, Kevin D.; Swarzenski, Peter W.; Crusius, John; Bratton, John F.; Charette, Matthew A.

    2006-01-01

    Eutrophication of coastal waters due to nonpoint source land-derived nitrogen (N) loads is a worldwide phenomenon and perhaps the greatest agent of change altering coastal ecology (National Research Council, 2000; Howarth and others, 2000). Within the United States, a majority of estuaries have been determined to be moderately to severely impaired by eutrophication associated with increasing nutrient loads (Bricker and others, 1999).In coastal watersheds with soils of high hydraulic conductivity and permeable coastal sediments, ground water is a major route of transport of freshwater and its solutes from land to sea. Freshwater flowing downgradient from aquifers may either discharge from a seepage face near the intertidal zone, or flow directly into the sea as submarine ground-water discharge (SGD) (fig. 1). In the coastal aquifer, entrainment of saline pore water occurs prior to discharge, producing a gradient in ground-water salinity from land to sea, referred to as a subterranean estuary (Moore, 1999). In addition, processes including density-driven flow and tidal pumping create brackish and saline ground-water circulation. Hence, submarine ground-water discharge often consists of a substantial amount of recirculating seawater. Mixing of fresh and saline ground waters in the context of coastal sediments may alter the chemical composition of the discharging fluid. Depending on the biogeochemical setting, removal of fixed N due to processes leading to N2 (dinitrogen gas) production in the nearshore aquifer and subterranean estuary may significantly attenuate land-derived N loads; or, processes such as ion exchange and tidal pumping in the subterranean estuary may substantially accelerate the transport of both land-derived and sediment re-mineralized N to estuarine water columns.As emphasized by Burnett and others (2001, 2002), a fundamental problem in evaluating the importance of ground-water discharge in marine geochemical budgets is the difficulty of collecting

  3. Urban Runoff and Nutrients Loading Control from Sustainable BMPs (Invited)

    Science.gov (United States)

    Xiao, Q.

    2009-12-01

    construction of runoff retention basins and treatment facilities to meet TMDL (Total Maximum Daily Load) regulations are not cost-effective or practical. An alternative approach is to control runoff and nutrients on-site through installation of decentralized BMPs that detain and infiltrate runoff before it reaches storm drains. Recent developed green-infrastructure which integrating engineered soil and trees to reduce runoff and nutrients loading is a self-sustained best management practice (BMP). This BMP has been testing and used in urban runoff control. In Davis, CA this type of BMPs were installed in a parking lot and a residential property to evaluate the system’s effectiveness on reducing storm runoff and pollutant loading from the parking lot and irrigated landscape. Storm runoff and pollutant loading were measured and monitored during February 2007 thru May 2009 from the parking lot. The BMP reduced surface runoff and nutrients by 88.8% and 95.3%, respectively. In the residential irrigated landscape, the dry-weather runoff was monitored during 2007 irrigation season, the BMP captured almost all dry weather runoff. The performance of these BMPs demonstrated their potential use for reducing runoff and nutrients loading. Control urban runoff from these 23% landscape (i.e., parking lot and irrigated turf grass) could largely alter the runoff and nutrients transport and their dynamic in our water system.

  4. Study of nonpoint source nutrient loading in the Patuxent River basin, Maryland

    Science.gov (United States)

    Preston, S.D.

    1997-01-01

    Study of nonpoint-source (NPS) nutrient loading in Maryland has focused on the Patuxent watershed because of its importance and representativeness of conditions in the State. Evaluation of NPS nutrient loading has been comprehensive and has included long-term monitoring, detailed watershed modeling, and synoptic sampling studies. A large amount of information has been compiled for the watershed and that information is being used to identify primary controls and efficient management strategies for NPS nutrient loading. Results of the Patuxent NPS study have identified spatial trends in water quality that appear to be related to basin charcteristics such as land use, physiography, andgeology. Evaluation of the data compiled by the study components is continuing and is expected to provide more detailed assessments of the reasons for spatial trends. In particular, ongoing evaluation of the watershed model output is expected to provide detailed information on the relative importance of nutrient sources and transport pathways across the entire watershed. Planned future directions of NPS evaluation in the State of Maryland include continued study of water quality in the Patuxent watershed and a shift in emphasis to a statewide approach. Eventually, the statewide approach will become the primary approach usedby the State to evaluate NPS loading. The information gained in the Patuxent study and the tools developed will represent valuable assets indeveloping the statewide NPS assessment program.

  5. Modeling nutrient transports and exchanges of nutrients between shallow regions and the open Baltic sea in present and future climate.

    Science.gov (United States)

    Eilola, Kari; Rosell, Elin Almroth; Dieterich, Christian; Fransner, Filippa; Höglund, Anders; Meier, H E Markus

    2012-09-01

    We quantified horizontal transport patterns and the net exchange of nutrients between shallow regions and the open sea in the Baltic proper. A coupled biogeochemical-physical circulation model was used for transient simulations 1961-2100. The model was driven by regional downscaling of the IPCC climate change scenario A1B from two global General Circulation Models in combination with two nutrient load scenarios. Modeled nutrient transports followed mainly the large-scale internal water circulation and showed only small circulation changes in the future projections. The internal nutrient cycling and exchanges between shallow and deeper waters became intensified, and the internal removal of phosphorus became weaker in the warmer future climate. These effects counteracted the impact from nutrient load reductions according to the Baltic Sea Action Plan. The net effect of climate change and nutrient reductions was an increased net import of dissolved inorganic phosphorus to shallow areas in the Baltic proper.

  6. Modeling global nutrient export from watersheds

    NARCIS (Netherlands)

    Kroeze, C.; Bouwman, L.|info:eu-repo/dai/nl/090428048; Seitzinger, S.

    2012-01-01

    We describe how global models can be used to analyze past and future trends in nutrient export from watersheds and how such models can be used to analyze causes and effects of coastal eutrophication. Future nutrient inputs to coastal waters may be higher than today, and nutrient ratios may depart

  7. The MANAGE database: nutrient load and site characteristic updates and runoff concentration data.

    Science.gov (United States)

    Harmel, Daren; Qian, Song; Reckhow, Ken; Casebolt, Pamela

    2008-01-01

    The "Measured Annual Nutrient loads from AGricultural Environments" (MANAGE) database was developed to be a readily accessible, easily queried database of site characteristic and field-scale nutrient export data. The original version of MANAGE, which drew heavily from an early 1980s compilation of nutrient export data, created an electronic database with nutrient load data and corresponding site characteristics from 40 studies on agricultural (cultivated and pasture/range) land uses. In the current update, N and P load data from 15 additional studies of agricultural runoff were included along with N and P concentration data for all 55 studies. The database now contains 1677 watershed years of data for various agricultural land uses (703 for pasture/rangeland; 333 for corn; 291 for various crop rotations; 177 for wheat/oats; and 4-33 yr for barley, citrus, vegetables, sorghum, soybeans, cotton, fallow, and peanuts). Across all land uses, annual runoff loads averaged 14.2 kg ha(-1) for total N and 2.2 kg ha(-1) for total P. On average, these losses represented 10 to 25% of applied fertilizer N and 4 to 9% of applied fertilizer P. Although such statistics produce interesting generalities across a wide range of land use, management, and climatic conditions, regional crop-specific analyses should be conducted to guide regulatory and programmatic decisions. With this update, MANAGE contains data from a vast majority of published peer-reviewed N and P export studies on homogeneous agricultural land uses in the USA under natural rainfall-runoff conditions and thus provides necessary data for modeling and decision-making related to agricultural runoff. The current version can be downloaded at http://www.ars.usda.gov/spa/manage-nutrient.

  8. Effects of climate and nutrient load on the water quality of shallow lakes assessed through ensemble runs by PCLake

    NARCIS (Netherlands)

    Nielsen, Anders; Trolle, Dennis; Bjerring, Rikke; Sondergaard, Martin; Olesen, Jorgen E.; Janse, Jan H.; Mooij, Wolf M.; Jeppesen, Erik

    2014-01-01

    Complex ecological models are used to predict the consequences of anticipated future changes in climate and nutrient loading for lake water quality. These models may, however, suffer from nonuniqueness in that various sets of model parameter values may yield equally satisfactory representations of

  9. Impact of organic nutrient load on biomass accumulation, feed channel pressure drop increase and permeate flux decline in membrane systems

    KAUST Repository

    Bucs, Szilard

    2014-12-01

    The influence of organic nutrient load on biomass accumulation (biofouling) and pressure drop development in membrane filtration systems was investigated. Nutrient load is the product of nutrient concentration and linear flow velocity. Biofouling - excessive growth of microbial biomass in membrane systems - hampers membrane performance. The influence of biodegradable organic nutrient load on biofouling was investigated at varying (i) crossflow velocity, (ii) nutrient concentration, (iii) shear, and (iv) feed spacer thickness. Experimental studies were performed with membrane fouling simulators (MFSs) containing a reverse osmosis (RO) membrane and a 31 mil thick feed spacer, commonly applied in practice in RO and nanofiltration (NF) spiral-wound membrane modules. Numerical modeling studies were done with identical feed spacer geometry differing in thickness (28, 31 and 34 mil). Additionally, experiments were done applying a forward osmosis (FO) membrane with varying spacer thickness (28, 31 and 34 mil), addressing the permeate flux decline and biofilm development. Assessed were the development of feed channel pressure drop (MFS studies), permeate flux (FO studies) and accumulated biomass amount measured by adenosine triphosphate (ATP) and total organic carbon (TOC).Our studies showed that the organic nutrient load determined the accumulated amount of biomass. The same amount of accumulated biomass was found at constant nutrient load irrespective of linear flow velocity, shear, and/or feed spacer thickness. The impact of the same amount of accumulated biomass on feed channel pressure drop and permeate flux was influenced by membrane process design and operational conditions. Reducing the nutrient load by pretreatment slowed-down the biofilm formation. The impact of accumulated biomass on membrane performance was reduced by applying a lower crossflow velocity and/or a thicker and/or a modified geometry feed spacer. The results indicate that cleanings can be delayed

  10. Transposing Concentration-Discharge Curves onto Unmonitored Catchments to Estimate Seasonal Nutrient Loads

    Science.gov (United States)

    Minaudo, C.; Moatar, F.; Abbott, B. W.; Dupas, R.; Gascuel-Odoux, C.; Pinay, G.; Roubeix, V.; Danis, P. A.

    2017-12-01

    Many lakes and reservoirs in Europe suffer from severe eutrophication. Accurate quantification of nutrient loads are critical for effective mitigation measures, but this information is often unknown. For example, in France, only 50 out of 481 lakes and reservoirs have national monitoring allowing estimation of interannual nitrogen and phosphorus loads, and even these loads are computed from low-frequency data. To address this lack of data, we developed a straightforward method to predict seasonal loads in lake tributaries. First, we analyzed concentration-discharge (C-Q) curves in monitored catchments and identified slopes, intercepts, and coefficient of variation of the log(C)-log(Q) regressions determined for both low and high flows, separated by the median daily flow [Moatar et al., 2017]. Then, we used stepwise multiple linear regression models to empirically link the characteristics of C-Q curves with a set of catchment descriptors such as land use, lithology, morphology indices, climate, and hydrological indicators. Modeled C-Q relationships were then used to estimate annual and seasonal nutrient loads in nearby and similar unmonitored catchments. We implemented this approach on a large dataset from France where stream flow was surveyed daily and water quality (suspended solids, nitrate, total phosphorus, and orthophosphate concentrations) was measured on a monthly basis at 233 stations over the past 20 years in catchments from 10 to 3000 km². The concentration at the median daily flow (seen here as a metric of the general level of contamination in a catchment) was predicted with uncertainty ranging between 30 and 100 %, depending on the variable. C-Q slopes were predicted with large errors, but a sensitivity analysis was conducted to determine the impact of C-Q slopes uncertainties on computed annual and seasonal loads. This approach allows estimation of seasonal and annual nutrient loads and could be potentially implemented to improve protection and

  11. Response of Vallisneria natans to Increasing Nitrogen Loading Depends on Sediment Nutrient Characteristics

    Directory of Open Access Journals (Sweden)

    Jiao Gu

    2016-11-01

    Full Text Available High nitrogen (N loading may contribute to recession of submerged macrophytes in shallow lakes; yet, its influences vary depending on environmental conditions. In August 2013, we conducted a 28-day factorial-designed field mesocosm experiment in Lake Taihu at the Taihu Laboratory for Lake Ecosystem Research (TLLER to examine the effects of high N loading on the growth of Vallisneria natans in systems with contrasting sediment types. We ran the experiments with two levels of nutrient loading—present-day external nutrient loading (average P: 5 μg·L−1·day−1, N: 130 μg·L−1·day−1 and P: 5 μg·L−1·day−1, and with three times higher N loading (N: 390 μg·L−1·day−1 and used sediment with two contrasting nutrient levels. V. natans growth decreased significantly with increasing N loading, the effect being dependent, however, on the nutrient status of the sediment. In low nutrient sediment, relative growth rates, leaf biomass and root biomass decreased by 11.9%, 18.2% and 23.3%, respectively, at high rather than low N loading, while the decline was larger (44.0%, 32.7% and 41.8%, respectively when using high nutrient sediment. The larger effect in the nutrient-rich sediment may reflect an observed higher shading of phytoplankton and excess nutrient accumulation in plant tissue, though potential toxic effects of the high-nutrient sediment may also have contributed. Our study confirms the occurrence of a negative effect of increasing N loading on submerged plant growth in shallow nutrient-enriched lakes and further shows that this effect is augmented when the plants grow in nutrient-rich sediment. External N control may, therefore, help to protect or restore submerged macrophytes, especially when the sediment is enriched with nutrients and organic matter.

  12. The assessment of nutrient loading and retention in the upper ...

    African Journals Online (AJOL)

    ... point of sewage outflow. High natural nutrient retention capacity of rivers ensures that the problem of wastewater disposal and diffuse pollution does not lead to eutrophication of downstream lakes and reservoirs. Management of the nutrient retention capacity of rivers is, therefore, central to sound watershed management ...

  13. Groundwater and stream threshold values for targeted and differentiated output based regulation of nutrient loadings to ecosystems

    Science.gov (United States)

    Hinsby, Klaus; Refsgaard, Jens Christian

    2015-04-01

    even field scale based on estimated acceptable nutrient loadings to transitional and coastal waters (or any other protected aquatic ecosystem in the river basin) according to the requirements of the EU Water Framework and Groundwater directives, and use these to monitor and plan sustainable water and land use management, e.g. by differentiated practices in farming and land use within sub-catchments. Specifically, we suggest that monitoring of the nitrogen outputs from catchments, sub-catchment and even delineated specific fields with new cost-effective monitoring systems in combination with coupled soil-groundwater-surface water models has a large potential for the development of efficient differentiated measures controlling nutrient loadings to aquatic ecosystems. Here we present initial considerations and suggestions for the development of new governance concepts targeted at differentiated output based regulations using threshold values for N in groundwater and streams derived from acceptable loadings to a small Danish estuary.

  14. Macro-grazer herbivory regulates seagrass response to pulse and press nutrient loading.

    Science.gov (United States)

    Ravaglioli, Chiara; Capocchi, Antonella; Fontanini, Debora; Mori, Giovanna; Nuccio, Caterina; Bulleri, Fabio

    2018-02-21

    Coastal ecosystems are exposed to multiple stressors. Predicting their outcomes is complicated by variations in their temporal regimes. Here, by means of a 16-month experiment, we investigated tolerance and resistance traits of Posidonia oceanica to herbivore damage under different regimes of nutrient loading. Chronic and pulse nutrient supply were combined with simulated fish herbivory, treated as a pulse stressor. At ambient nutrient levels, P. oceanica could cope with severe herbivory, likely through an increase in photosynthetic activity. Elevated nutrient levels, regardless of the temporal regime, negatively affected plant growth and increased leaf nutritional quality. This ultimately resulted in a reduction of plant biomass that was particularly severe under chronic fertilization. Our results suggest that both chronic and pulse nutrient loadings increase plant palatability to macro-grazers. Strategies for seagrass management should not be exclusively applied in areas exposed to chronic fertilization since even short-term nutrient pulses could alter seagrass meadows. Copyright © 2018 Elsevier Ltd. All rights reserved.

  15. Spatial identification of critical nutrient loads of large shallow lakes: Implications for Lake Taihu (China)

    NARCIS (Netherlands)

    Janssen, A.B.G.; de Jager, V.C.L.; Janse, J.H.; Kong, X.; Liu, S.; Ye, W.M.; Mooij, W.M.

    2017-01-01

    Ongoing eutrophication frequently causes toxic phytoplankton blooms. This induces huge worldwide challenges for drinking water quality, food security and public health. Of crucial importance in avoiding and reducing blooms is to determine the maximum nutrient load ecosystems can absorb, while

  16. 9 Nutrient Load of the Sakumo Lagoon.cdr

    African Journals Online (AJOL)

    Administrator

    cycles of marine fish and prawn species, as well as fisheries further ... Pollution of the lagoon with nutrients can affect biodiversity of plant and animal species, especially water fowls and birds ecology, since the site is noted for its large number of birds (Ntiamoa- ... found along most of the river courses within the Ramsar site.

  17. Nutrient loads in the river mouth of the Río Verde basin in Jalisco, Mexico: how to prevent eutrophication in the future reservoir?

    Science.gov (United States)

    Jayme-Torres, Gonzalo; Hansen, Anne M

    2017-10-04

    Since nutrients are emitted and mobilized in river basins, causing eutrophication of water bodies, it is important to reduce such emissions and subsequent nutrient loads. Due to processes of attenuation, nutrient loads are reduced during their mobilization in river basins. At the mouth of the Río Verde basin in western Mexico, the El Purgatorio dam is being constructed to supply water to the metropolitan area of the second most populated city in the country, Guadalajara. To analyze situations that allow protecting this future dam from eutrophication, nutrient loads in the mouth of the river basin were determined and their reduction scenarios evaluated by using the NEWS2 (Nutrient Export from Watersheds) model. For this, a nutrient emissions inventory was established and used to model nutrient loads, and modeling results were compared to an analysis of water quality data from two different monitoring sites located on the river. The results suggest that 96% of nitrogen and 99% of phosphorus emissions are attenuated in the watershed. Nutrient loads reaching the mouth of the river basin come mainly from wastewater discharges, followed by livestock activities and different land uses, and loads are higher as emissions are located closer to the mouth of the river basin. To achieve and maintain mesotrophic state of water in the future dam, different nutrient emission reduction scenarios were evaluated. According to these results, the reduction of 90% of the phosphorus loads in wastewater emissions or 75% of the phosphorus loads in wastewater emissions and at least 50% in emissions from livestock activities in the river basin are required.

  18. Best management practices for reducing nutrient loads in a sub-watershed of Chesapeake Bay

    Science.gov (United States)

    Water quality improvement in the Chesapeake Bay is a grave concern. An initiative to reduce the nutrient loads to stream has been undertaken to attain a target total maximum daily load (TMDL) at Chesapeake Bay. A general guideline with a set of best management practices (BMPs) has been in place for ...

  19. Best management practices for reducing nutrient loads in a sub-watershed of Chesapeake Bay area

    Science.gov (United States)

    Water quality improvement in the Chesapeake Bay is a grave concern. An initiative to reduce the nutrient loads to stream has been undertaken to attain a target total maximum daily load (TMDL) at Chesapeake Bay. A general guideline with a set of best management practices (BMPs) has been in place for ...

  20. Modeling nutrient filtering capacities and export fluxes in macrotidal estuaries

    Science.gov (United States)

    Regnier, P.; Arndt, S.; Savenije, H.; Vanderborght, J.-P.

    2009-04-01

    A fully transient model of a macrotidal estuary (The Scheldt) has been used to quantify silica and nitrogen filtering capacities and export fluxes to the coastal zone over a period of one year. Results show that in macrotidal estuaries, the seasonally-resolved nutrient fluxes are not only affected by in-situ biogeochemical transformations, but also by nutrient flux imbalances, which result from the time-lagged response of the scalar fields to hydrological perturbations. The estuarine nutrient retention reveals also a strong temporal variability, which is driven by the complex interplay between reaction and transport. As a result, the estuarine filtering capacities cannot be constrained by the freshwater residence alone and, thus, by empirical relationships that have been established between these two parameters. Furthermore, at the seasonal scale, the nutrient export fluxes to the coastal zone cannot be quantified from the riverine loads and the estuarine filtering capacities. More sophisticated approaches to estimate the functioning and response of macrotidal estuaries are thus needed and an alternative methodology, established on the premise that physical forcing mechanisms are the dominant controls on estuarine biogeochemistry at a series of hierarchically related system levels, is briefly outlined.

  1. A Geographic Information System approach to modeling nutrient and sediment transport

    Energy Technology Data Exchange (ETDEWEB)

    Levine, D.A. [Automated Sciences Group, Inc., Oak Ridge, TN (United States); Hunsaker, C.T.; Beauchamp, J.J. [Oak Ridge National Lab., TN (United States); Timmins, S.P. [Analysas Corp., Oak Ridge, TN (United States)

    1993-02-01

    The objective of this study was to develop a water quality model to quantify nonpoint-source (NPS) pollution that uses a geographic information system (GIS) to link statistical modeling of nutrient and sediment delivery with the spatial arrangement of the parameters that drive the model. The model predicts annual nutrient and sediment loading and was developed, calibrated, and tested on 12 watersheds within the Lake Ray Roberts drainage basin in north Texas. Three physiographic regions are represented by these watersheds, and model success, as measured by the accuracy of load estimates, was compared within and across these regions.

  2. Retention of riverine sediment and nutrient loads by coastal plain floodplains

    Science.gov (United States)

    Noe, G.B.; Hupp, C.R.

    2009-01-01

    Despite the frequent citation of wetlands as effective regulators of water quality, few quantitative estimates exist for their cumulative retention of the annual river loads of nutrients or sediments. Here we report measurements of sediment accretion and associated carbon, nitrogen, and phosphorus accumulation as sedimentation over feldspar marker horizons placed on floodplains of the non-tidal, freshwater Coastal Plain reaches of seven rivers in the Chesapeake Bay watershed, USA. We then scale these accumulation rates to the entire extent of non-tidal floodplain in the Coastal Plain of each river, defined as riparian area extending from the Fall Line to the upper limit of tidal influence, and compare them to annual river loads. Floodplains accumulated a very large amount of material compared to their annual river loads of sediment (median among rivers = 119%), nitrogen (24%), and phosphorus (59%). Systems with larger floodplain areas and longer floodplain inundation retained greater proportions of riverine loads of nitrogen and phosphorus, but systems with larger riverine loads retained a smaller proportion of that load on floodplains. Although the source and long-term fate of deposited sediment and associated nutrients are uncertain, these fluxes represent the interception of large amounts of material that otherwise could have been exported downstream. Coastal Plain floodplain ecosystems are important regulators of sediment, carbon, and nutrient transport in watersheds of the Chesapeake Bay.

  3. Historical changes in optical properties of Roskilde Fjord, during a period of decreasing nutrient load

    DEFF Research Database (Denmark)

    Pedersen, Troels Møller; Nielsen, Søren Laurentius; Jensen, Kaj Sand

    Loss of water clarity is a common consequence of coastal eutrophication. Efforts have been made to reduce the nutrient load of the inner Danish waters, hence increasing water column clarity. Measurements of Light attenuation, Particulate Organic Matter (POM) and Chlorophyll a (Chl a) concentrations...

  4. Connecting fishery sustainability to estuarine habitats and nutrient loading

    Science.gov (United States)

    The production of several important fishery species depends on critical estuarine habitats, including seagrasses and salt marshes. Relatively simple models can be constructed to relate fishery productivity to the extent and distribution of these habitats by linking fishery-depend...

  5. Effects of climate and nutrient load on the water quality of shallow lakes assessed through ensemble runs by PCLake.

    Science.gov (United States)

    Nielsen, Anders; Trolle, Dennis; Bjerring, Rikke; Søndergaard, Martin; Olesen, Jørgen E; Janse, Jan H; Mooij, Wolf M; Jeppesen, Erik

    Complex ecological models are used to predict the consequences of anticipated future changes in climate and nutrient loading for lake water quality. These models may, however, suffer from nonuniqueness in that various sets of model parameter values may yield equally satisfactory representations of the system being modeled, but when applied in future scenarios these sets of values may divert considerably in their simulated outcomes. Compilation of an ensemble of model runs allows us to account for simulation variability arising from model parameter estimates. Thus, we propose a new approach for aquatic ecological models creating a more robust prediction of future water quality. We used our ensemble approach in an application of the widely used PCLake model for Danish shallow Lake Arreskov, which during the past two decades has demonstrated frequent shifts between turbid and clear water states. Despite marked variability, the span of our ensemble runs encapsulated 70–90% of the observed variation in lake water quality. The model exercise demonstrates that future warming and increased nutrient loading lead to lower probability of a clear water, vegetation-rich state and greater likelihood of cyanobacteria dominance. In a 6.0°C warming scenario, for instance, the current nutrient loading of nitrogen and phosphorus must be reduced by about 75% to maintain the present ecological state of Lake Arreskov, but even in a near-future 2.0°C warming scenario, a higher probability of a turbid, cyanobacteria-dominated state is predicted. As managers may wish to determine the probability of achieving a certain ecological state, our proposed ensemble approach facilitates new ways of communicating future stressor impacts.

  6. Temporal responses of coastal hypoxia to nutrient loading and physical controls

    Directory of Open Access Journals (Sweden)

    W. M. Kemp

    2009-12-01

    Full Text Available The incidence and intensity of hypoxic waters in coastal aquatic ecosystems has been expanding in recent decades coincident with eutrophication of the coastal zone. Worldwide, there is strong interest in reducing the size and duration of hypoxia in coastal waters, because hypoxia causes negative effects for many organisms and ecosystem processes. Although strategies to reduce hypoxia by decreasing nutrient loading are predicated on the assumption that this action would reverse eutrophication, recent analyses of historical data from European and North American coastal systems suggest little evidence for simple linear response trajectories. We review published parallel time-series data on hypoxia and loading rates for inorganic nutrients and labile organic matter to analyze trajectories of oxygen (O2 response to nutrient loading. We also assess existing knowledge of physical and ecological factors regulating O2 in coastal marine waters to facilitate analysis of hypoxia responses to reductions in nutrient (and/or organic matter inputs. Of the 24 systems identified where concurrent time series of loading and O2 were available, half displayed relatively clear and direct recoveries following remediation. We explored in detail 5 well-studied systems that have exhibited complex, non-linear responses to variations in loading, including apparent "regime shifts". A summary of these analyses suggests that O2 conditions improved rapidly and linearly in systems where remediation focused on organic inputs from sewage treatment plants, which were the primary drivers of hypoxia. In larger more open systems where diffuse nutrient loads are more important in fueling O2 depletion and where climatic influences are pronounced, responses to remediation tended to follow non-linear trends that may include hysteresis and time-lags. Improved understanding of hypoxia remediation requires that future studies use

  7. Temporal responses of coastal hypoxia to nutrient loading and physical controls

    Science.gov (United States)

    Kemp, W. M.; Testa, J. M.; Conley, D. J.; Gilbert, D.; Hagy, J. D.

    2009-12-01

    The incidence and intensity of hypoxic waters in coastal aquatic ecosystems has been expanding in recent decades coincident with eutrophication of the coastal zone. Worldwide, there is strong interest in reducing the size and duration of hypoxia in coastal waters, because hypoxia causes negative effects for many organisms and ecosystem processes. Although strategies to reduce hypoxia by decreasing nutrient loading are predicated on the assumption that this action would reverse eutrophication, recent analyses of historical data from European and North American coastal systems suggest little evidence for simple linear response trajectories. We review published parallel time-series data on hypoxia and loading rates for inorganic nutrients and labile organic matter to analyze trajectories of oxygen (O2) response to nutrient loading. We also assess existing knowledge of physical and ecological factors regulating O2 in coastal marine waters to facilitate analysis of hypoxia responses to reductions in nutrient (and/or organic matter) inputs. Of the 24 systems identified where concurrent time series of loading and O2 were available, half displayed relatively clear and direct recoveries following remediation. We explored in detail 5 well-studied systems that have exhibited complex, non-linear responses to variations in loading, including apparent "regime shifts". A summary of these analyses suggests that O2 conditions improved rapidly and linearly in systems where remediation focused on organic inputs from sewage treatment plants, which were the primary drivers of hypoxia. In larger more open systems where diffuse nutrient loads are more important in fueling O2 depletion and where climatic influences are pronounced, responses to remediation tended to follow non-linear trends that may include hysteresis and time-lags. Improved understanding of hypoxia remediation requires that future studies use comparative approaches and consider multiple regulating factors. These analyses

  8. Estimation of transported pollutant load in Ardila catchment using the SWAT model

    OpenAIRE

    DURÃO, A.; LEITÃO, P.; BRITO, D.; FERNANDES, R.M.; NEVES, R.; MORAIS, M.

    2011-01-01

    Excess of organic matter and nutrients in the water body promotes algae blooms, which can accelerate the eutrophication process, situation often observed in the Ardila river. This river was identified as very polluted and classified as critical for Alqueva-Pedrogão System. The aim of this study was to estimate the transported nutrients load in a transboundary catchment using the SWAT (Soil and Water Assessment Tool) model and to determine the contribution off nutrients load in the entire catc...

  9. Nutrient and sediment concentrations and corresponding loads during the historic June 2008 flooding in eastern Iowa

    Science.gov (United States)

    Hubbard, L.; Kolpin, D.W.; Kalkhoff, S.J.; Robertson, Dale M.

    2011-01-01

    A combination of above-normal precipitation during the winter and spring of 2007-2008 and extensive rainfall during June 2008 led to severe flooding in many parts of the midwestern United States. This resulted in transport of substantial amounts of nutrients and sediment from Iowa basins into the Mississippi River. Water samples were collected from 31 sites on six large Iowa tributaries to the Mississippi River to characterize water quality and to quantify nutrient and sediment loads during this extreme discharge event. Each sample was analyzed for total nitrogen, dissolved nitrate plus nitrite nitrogen, dissolved ammonia as nitrogen, total phosphorus, orthophosphate, and suspended sediment. Concentrations measured near peak flow in June 2008 were compared with the corresponding mean concentrations from June 1979 to 2007 using a paired t test. While there was no consistent pattern in concentrations between historical samples and those from the 2008 flood, increased flow during the flood resulted in near-peak June 2008 flood daily loads that were statistically greater (p phosphorus (P) leaving Iowa, which accounted for about 22 and 46% of the total average annual nutrient yield, respectively. This study demonstrates the importance of large flood events to the total annual nutrient load in both small streams and large rivers.

  10. Direct groundwater discharge and vulnerability to hidden nutrient loads along the Great Lakes coast of the United States

    Science.gov (United States)

    Knights, Deon; Parks, Kevin C.; Sawyer, Audrey H.; David, Cédric H.; Browning, Trevor N.; Danner, Kelsey M.; Wallace, Corey D.

    2017-11-01

    Direct groundwater discharge delivers nutrients from land and lakebed sediments to the Great Lakes, which impacts lake water quality. Broad spatial distributions of discharging groundwater are often difficult to measure directly. We present high resolution estimates of direct groundwater discharge across 43% of the Great Lakes coastline based on a water budget approach that uses hydroclimatic models and high-resolution hydrographic data available within the United States. We also integrate land use data to identify coastal areas vulnerable to high groundwater-borne nutrient loads. Estimated rates of direct groundwater discharge along the Great Lakes coast are highly variable, but generally are greatest for Lake Erie and Lake Michigan. Almost one-third of Lake Erie's United States coastline is vulnerable to groundwater sources of nutrients. To assess uncertainties and limitations in our vulnerability analysis, a vulnerable site along Lake Erie was selected for detailed field measurements of direct groundwater discharge rates and nutrient fluxes. Measured discharge rates were significantly lower than water budget-based estimates (354 ± 25 m3 y-1 m-1 compared to 588 ± 181 m3 y-1 m-1). Dissolved phosphorous concentrations in the lakebed were elevated compared to onshore groundwater, while nitrate concentrations were lower, indicative of a highly reactive sediment-water interface. Some of the measured phosphorus may be locally sourced from desorption of legacy P or mineralization of organic matter in the lakebed, which our vulnerability framework does not include. Much of the land-derived nitrogen may be transformed along groundwater flow paths prior to discharge. While model-based estimates of direct groundwater discharge and vulnerability to nutrient loading are important for managing Great Lakes water quality, direct field observations remain essential for quantifying fluxes.

  11. Nutrient cycle benchmarks for earth system land model

    Science.gov (United States)

    Zhu, Q.; Riley, W. J.; Tang, J.; Zhao, L.

    2017-12-01

    Projecting future biosphere-climate feedbacks using Earth system models (ESMs) relies heavily on robust modeling of land surface carbon dynamics. More importantly, soil nutrient (particularly, nitrogen (N) and phosphorus (P)) dynamics strongly modulate carbon dynamics, such as plant sequestration of atmospheric CO2. Prevailing ESM land models all consider nitrogen as a potentially limiting nutrient, and several consider phosphorus. However, including nutrient cycle processes in ESM land models potentially introduces large uncertainties that could be identified and addressed by improved observational constraints. We describe the development of two nutrient cycle benchmarks for ESM land models: (1) nutrient partitioning between plants and soil microbes inferred from 15N and 33P tracers studies and (2) nutrient limitation effects on carbon cycle informed by long-term fertilization experiments. We used these benchmarks to evaluate critical hypotheses regarding nutrient cycling and their representation in ESMs. We found that a mechanistic representation of plant-microbe nutrient competition based on relevant functional traits best reproduced observed plant-microbe nutrient partitioning. We also found that for multiple-nutrient models (i.e., N and P), application of Liebig's law of the minimum is often inaccurate. Rather, the Multiple Nutrient Limitation (MNL) concept better reproduces observed carbon-nutrient interactions.

  12. Groundwater flux and nutrient loading in the northeast section of Bear Lake, Muskegon County, Michigan, 2015

    Science.gov (United States)

    Totten, Alexander R.; Maurer, Jessica A.; Duris, Joseph W.

    2017-11-30

    Bear Lake in North Muskegon, Michigan, is listed as part of the Muskegon Lake area of concern as designated by the U.S. Environmental Protection Agency. This area of concern was designated as a result of eutrophication and beneficial use impairments. On the northeast end of Bear Lake, two man-made retention ponds (Willbrandt Pond East and Willbrandt Pond West), formerly used for celery farming, may contribute nutrients to Bear Lake. Willbrandt Ponds (East and West) were previously muck fields that were actively used for celery farming from the early 1900s until 2002. The restoration and reconnection of the Willbrandt Ponds into Bear Lake prompted concerns of groundwater nutrient loading into Bear Lake. Studies done by the State of Michigan and Grand Valley State University revised initial internal phosphorus load estimates and indicated an imbalance in the phosphorus budget in Bear Lake. From June through November 2015, the U.S. Geological Survey (USGS) did an investigative study to quantify the load of nutrients from shallow groundwater around the Willbrandt Ponds in an effort to update the phosphorus budget to Bear Lake. Seven sampling locations were established, including five shallow groundwater wells and two surface-water sites, in the Willbrandt pond study area and Bear Lake. A total of 12 nutrient samples and discrete water-level measurements were collected from each site from June through November 2015. Continuous water-level data were recorded for both surface-water monitoring locations for the entire sampling period.Water-level data indicated that Willbrandt Pond West had the highest average water-level elevation of all sites monitored, which indicated the general direction of flux is from Willbrandt Pond West to Bear Lake. Nutrient and chloride loading from Willbrandt Pond West to Bear Lake was calculated using two distinct methods: Dupuit and direct seepage methods. Shallow groundwater loading calculations were determined by using groundwater levels to

  13. Usefulness of Models in Precision Nutrient Management

    DEFF Research Database (Denmark)

    Plauborg, Finn; Manevski, Kiril; Zhenjiang, Zhou

    characterize soil condition by mapping a variety of physical-chemical properties including salinity, water content, texture, bulk density. vis–NIR spectroscopy shows the potential for use directly for the characterisation of soil quality, or soil fertility as the spectra contain information on soil organic...... and mineral composition. Mapping of crop status and the spatial-temporal variability within fields with red-infrared reflection are used to support decision on split fertilisation and more precise dosing. The interpretation and use of these various data in precise nutrient management is not straightforward......, especially as the various soil and crop state variables or indicators are a result of several processes integrated over time. The present paper explore the possibility to use a physically based model to interpret the spatial variable data and if the model sensitivity to changes in input my lead to a valid...

  14. Nutrient Loads Flowing into Coastal Waters from the Main Rivers of China (2006–2012)

    Science.gov (United States)

    Tong, Yindong; Zhao, Yue; Zhen, Gengchong; Chi, Jie; Liu, Xianhua; Lu, Yiren; Wang, Xuejun; Yao, Ruihua; Chen, Junyue; Zhang, Wei

    2015-01-01

    Based on monthly monitoring data of unfiltered water, the nutrient discharges of the eight main rivers flowing into the coastal waters of China were calculated from 2006 to 2012. In 2012, the total load of NH3-N (calculated in nitrogen), total nitrogen (TN, calculated in nitrogen) and total phosphorus (TP, calculated in phosphorus) was 5.1 × 105, 3.1 × 106 and 2.8 × 105 tons, respectively, while in 2006, the nutrient load was 7.4 × 105, 2.2 × 106 and 1.6 × 105 tons, respectively. The nutrient loading from the eight major rivers into the coastal waters peaked in summer and autumn, probably due to the large water discharge in the wet season. The Yangtze River was the largest riverine nutrient source for the coastal waters, contributing 48% of the NH3-N discharges, 66% of the TN discharges and 84% of the TP discharges of the eight major rivers in 2012. The East China Sea received the majority of the nutrient discharges, i.e. 50% of NH3-N (2.7 × 105 tons), 70% of TN (2.2 × 106 tons) and 87% of TP (2.5 × 105 tons) in 2012. The riverine discharge of TN into the Yellow Sea and Bohai Sea was lower than that from the direct atmospheric deposition, while for the East China Sea, the riverine TN input was larger. PMID:26582206

  15. Nutrient Loads Flowing into Coastal Waters from the Main Rivers of China (2006-2012).

    Science.gov (United States)

    Tong, Yindong; Zhao, Yue; Zhen, Gengchong; Chi, Jie; Liu, Xianhua; Lu, Yiren; Wang, Xuejun; Yao, Ruihua; Chen, Junyue; Zhang, Wei

    2015-11-19

    Based on monthly monitoring data of unfiltered water, the nutrient discharges of the eight main rivers flowing into the coastal waters of China were calculated from 2006 to 2012. In 2012, the total load of NH3-N (calculated in nitrogen), total nitrogen (TN, calculated in nitrogen) and total phosphorus (TP, calculated in phosphorus) was 5.1 × 10(5), 3.1 × 10(6) and 2.8 × 10(5) tons, respectively, while in 2006, the nutrient load was 7.4 × 10(5), 2.2 × 10(6) and 1.6 × 10(5) tons, respectively. The nutrient loading from the eight major rivers into the coastal waters peaked in summer and autumn, probably due to the large water discharge in the wet season. The Yangtze River was the largest riverine nutrient source for the coastal waters, contributing 48% of the NH3-N discharges, 66% of the TN discharges and 84% of the TP discharges of the eight major rivers in 2012. The East China Sea received the majority of the nutrient discharges, i.e. 50% of NH3-N (2.7 × 10(5) tons), 70% of TN (2.2 × 10(6) tons) and 87% of TP (2.5 × 10(5) tons) in 2012. The riverine discharge of TN into the Yellow Sea and Bohai Sea was lower than that from the direct atmospheric deposition, while for the East China Sea, the riverine TN input was larger.

  16. Quantifying Nutrient and Mercury Concentrations and Loads in Lake Tahoe Snowpack

    Science.gov (United States)

    Pearson, C.; Obrist, D.; Schumer, R.

    2012-12-01

    Recent climate models predict a large decrease in Sierra Nevada snowpack over the next fifty years as a result of climate change. This decrease will not only affect the hydrologic balance but also change inputs of nutrients and pollutants through atmospheric deposition. In the Lake Tahoe basin, winter precipitation dominates and snowfall provides approximately 70 percent of the annual water input. From the first snowfall until the end of melting, snowpack acts as a temporary storage for atmospheric deposition that accumulates throughout winter and spring. Through melt and runoff processes, these nutrients and pollutants can enter the aquatic ecosystem where they can have detrimental effects on lake clarity and health. Most previous studies in this basin have focused on direct atmospheric deposition loads to the lake surface, and little temporal and spatial information is available on the dynamics of atmospheric deposition in the basin's snowpack. We here present nitrogen (N), phosphorus (P), and mercury (Hg) concentrations and pool sizes in snowpack along two elevational transects in the Tahoe Basin from January to April of 2012. Total N and P concentrations in the snowpack ranged from 0.07 mg/L to 0.38 mg/L and 0.003 mg/L to 0.109 mg/L, respectively. P concentrations showed strong increases from the west-side to the east-side of the basin which we attribute to local (e.g., urban or road-dust), in-basin sources that are distributed along the dominant west-wind patterns. N species, on the other hand, generally showed little spatial trends, indicating that its sources were more diffuse and possibly from out-of- basin. Hg concentrations ranged from 0.81 ppt to 6.25 ppt and showed similar spatial patterns as N. Hg, however, also showed significant snowpack concentration decreases during storm-free periods which we attribute to gaseous losses of Hg back to the atmosphere from photochemical reduction. These emissions are further supported by lower Hg concentrations in

  17. Nutrient and sediment concentrations and loads in the Steele Bayou Basin, northwestern Mississippi, 2010–14

    Science.gov (United States)

    Hicks, Matthew B.; Murphy, Jennifer C.; Stocks, Shane J.

    2017-06-01

    The U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers-Vicksburg District, monitored streamflow, water quality, and sediment at two stations on the Steele Bayou in northwestern Mississippi from October 2010 through September 2014 to characterize nutrient and sediment concentrations and loads in areas where substantial implementation of conservation efforts have been implemented. The motivation for this effort was to quantify improvements, or lack thereof, in water quality in the Steele Bayou watershed as a result of implementing large- and small-scale best-management practices aimed at reducing nutrient and sediment concentrations and loads. The results of this study document the hydrologic, water-quality, and sedimentation status of these basins following over two decades of ongoing implementation of conservation practices.Results from this study indicate the two Steele Bayou stations have comparable loads and yields of total nitrogen, phosphorus, and suspended sediment when compared to other agricultural basins in the southeastern and central United States. However, nitrate plus nitrite yields from basins in the Mississippi River alluvial plain, including the Steele Bayou Basin, are generally lower than other agricultural basins in the southeastern and central United States.Seasonal variation in nutrient and sediment loads was observed at both stations and for most constituents. About 50 percent of the total annual nutrient and sediment load was observed during the spring (February through May) and between 25 and 50 percent was observed during late fall and winter (October through January). These seasonal patterns probably reflect a combination of seasonal patterns in precipitation, runoff, streamflow, and in the timing of fertilizer application.Median concentrations of total nitrogen, nitrate plus nitrite, total phosphorus, orthophosphate, and suspended sediment were slightly higher at the upstream station, Steele Bayou near Glen Allan

  18. Simple model for dice loading

    Science.gov (United States)

    Nagler, Jan; Richter, Peter H.

    2010-03-01

    Dice tossing is commonly believed to be random. However, throwing a fair cube is a dissipative process that is well described by deterministic classical mechanics. In Nagler and Richter (2008 Phys. Rev. E 78 036207; featured in 2008 Nature 455 434), we proposed a simplified model to analyze the origin of the pseudorandomness: a barbell with two masses at its tips with only two final outcomes. In order to keep things simple, we focused on the symmetrical case of equal masses. Here, we complete the picture by considering the general asymmetric case of unequal masses. We show how, depending on the initial conditions, dissipation during bounces, and mass asymmetry, the degree of unpredictability varies. Our analysis reveals, for the simplest possible non-trivial dice throwing model, the effect of dice loading. A surprising consequence of dynamical resonances is that an experienced player may benefit sometimes more from an unloaded than from a loaded barbell. In addition, we investigate the influence of loading on the symmetry breaking process causing one mass to come to rest earlier than the others.

  19. Evaluation of nutrient retention in vegetated filter strips using the SWAT model.

    Science.gov (United States)

    Elçi, Alper

    2017-11-01

    Nutrient fluxes in stream basins need to be controlled to achieve good water quality status. In stream basins with intensive agricultural activities, nutrients predominantly come from diffuse sources. Therefore, best management practices (BMPs) are increasingly implemented to reduce nutrient input to streams. The objective of this study is to evaluate the impact of vegetated filter strip (VFS) application as an agricultural BMP. For this purpose, SWAT is chosen, a semi-distributed water quality assessment model that works at the watershed scale, and applied on the Nif stream basin, a small-sized basin in Western Turkey. The model is calibrated with an automated procedure against measured monthly discharge data. Nutrient loads for each sub-basin are estimated considering basin-wide data on chemical fertilizer and manure usage, population data for septic tank effluents and information about the land cover. Nutrient loads for 19 sub-basins are predicted on an annual basis. Average total nitrogen and total phosphorus loads are estimated as 47.85 t/yr and 13.36 t/yr for the entire basin. Results show that VFS application in one sub-basin offers limited retention of nutrients and that a selection of 20-m filter width is most effective from a cost-benefit perspective.

  20. Climate change and agricultural development: adapting Polish agriculture to reduce future nutrient loads in a coastal watershed.

    Science.gov (United States)

    Piniewski, Mikołaj; Kardel, Ignacy; Giełczewski, Marek; Marcinkowski, Paweł; Okruszko, Tomasz

    2014-09-01

    Currently, there is a major concern about the future of nutrient loads discharged into the Baltic Sea from Polish rivers because they are main contributors to its eutrophication. To date, no watershed-scale studies have properly addressed this issue. This paper fills this gap by using a scenario-modeling framework applied in the Reda watershed, a small (482 km²) agricultural coastal area in northern Poland. We used the SWAT model to quantify the effects of future climate, land cover, and management changes under multiple scenarios up to the 2050s. The combined effect of climate and land use change on N-NO3 and P-PO4 loads is an increase by 20-60 and 24-31 %, respectively, depending on the intensity of future agricultural usage. Using a scenario that assumes a major shift toward a more intensive agriculture following the Danish model would bring significantly higher crop yields but cause a great deterioration of water quality. Using vegetative cover in winter and spring (VC) would be a very efficient way to reduce future P-PO4 loads so that they are lower than levels observed at present. However, even the best combination of measures (VC, buffer zones, reduced fertilization, and constructed wetlands) would not help to remediate heavily increased N-NO3 loads due to climate change and agricultural intensification.

  1. The effect of restored and native oxbows on hydraulic loads of nutrients and stream water quality

    Science.gov (United States)

    Kalkhoff, Stephen J.; Hubbard, Laura E.; Joseph P.Schubauer-Berigan,

    2016-01-01

    The use of oxbow wetlands has been identified as a potential strategy to reduce nutrient transport from agricultural drainage tiles to streams in Iowa. In 2013 and 2014, a study was conducted in north-central Iowa in a native oxbow in the Lyons Creek watershed and two restored oxbow wetlands in the Prairie Creek watershed (Smeltzer west and Smeltzer east) to assess their effectiveness at reducing nitrogen and phosphorus loads. The tile line inlets carrying agricultural runoff to the oxbows, the outfall from the oxbows, and the surface waters in the streams receiving the outfall water were monitored for discharge and nutrients from February 2013 to September 2015. Smeltzer west and east also had four monitoring wells each, two in the upland and two between the oxbow and Prairie Creek to monitor surface water-groundwater interaction. The Smeltzer west and east oxbow sites also were instrumented to continuously measure the nitrate concentration. Rainfall was measured at one Lyons Creek and one Smeltzer site. Daily mean nitrate-N concentrations in Lyons Creek in 2013 ranged from 11.8 mg/L to 40.9 mg/L, the median daily mean nitrate-N concentration was 33.0 mg/L. Daily mean nitrate-N concentrations in Prairie Creek in 2013 ranged from 0.07 mg/L in August to 32.2 mg/L in June. In 2014, daily mean nitrate-N concentrations in Prairie Creek ranged from 0.17 mg/L in April to 26.7 mg/L in July; the daily mean nitrate-N concentration for the sampled period was 9.78 mg/L. Nutrient load reduction occurred in oxbow wetlands in Lyons and Prairie Creek watersheds in north-central Iowa but efficiency of reduction was variable. Little nutrient reduction occurred in the native Lyons Creek oxbow during 2013. Concentrations of all nutrient constituents were not significantly (P>0.05, Wilcoxon rank sum) different in water discharging from the tile line than in water leaving the Lyons Creek oxbow. A combination of physical features and flow conditions suggest that the residence time of

  2. Dynamic load modeling using neural networks

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, C.; Silva, A.P. Alves da; Torres, G. Lambert [Escola Federal de Engenharia de Itajuba, MG (Brazil). Inst. de Engenharia Eletrica

    1996-07-01

    Accurate dynamic load models allow more precise calculations of power system controls and stability limits. System identification methods can be applied to estimate load models based on measurements. Parametric and nonparametric are the two classes in system identification methods. The parametric approach has been the only one used for load modeling so far. In this paper, the performance of a nonparametric load model based on the functional polynomial artificial neural network is compared with a linear model and with the popular Zip model. The impact of clustering different load compositions is also investigated. Substation buses (138 kV) from the Brazilian system feeding important industrial consumers have been modeled. (author)

  3. Land cover models to predict non-point nutrient inputs for selected ...

    African Journals Online (AJOL)

    WQSAM is a practical water quality model for use in guiding southern African water quality management. However, the estimation of non-point nutrient inputs within WQSAM is uncertain, as it is achieved through a combination of calibration and expert knowledge. Non-point source loads can be correlated to particular land ...

  4. Mathematical model of the bacteria-nutrient dynamics | Inyama ...

    African Journals Online (AJOL)

    In this paper we developed a Mathematical Model of bacteria-nutrient dynamics which results in a system of first order ordinary differential equations. The analysis of the model was done using dynamical systems. It was found out that the product of the maximum nutrient uptake per cel; and the number of cells produced per ...

  5. Relation of nutrient concentrations, nutrient loading, and algal production to changes in water levels in Kabetogama Lake, Voyageurs National Park, northern Minnesota, 2008-09

    Science.gov (United States)

    Christensen, Victoria G.; Maki, Ryan P.; Kiesling, Richard L.

    2011-01-01

    Nutrient enrichment has led to excessive algal growth in Kabetogama Lake, Voyageurs National Park, northern Minnesota. Water- and sediment-quality data were collected during 2008-09 to assess internal and external nutrient loading. Data collection was focused in Kabetogama Lake and its inflows, the area of greatest concern for eutrophication among the lakes of Voyageurs National Park. Nutrient and algal data were used to determine trophic status and were evaluated in relation to changes in Kabetogama Lake water levels following changes to dam operation starting in 2000. Analyses were used to estimate external nutrient loading at inflows and assess the potential contribution of internal phosphorus loading. Kabetogama Lake often was mixed vertically, except for a few occasionally stratified areas, including Lost Bay in the northeastern part of Kabetogama Lake. Stratification, combined with larger bottom-water nutrient concentrations, larger sediment phosphorus concentrations, and estimated phosphorus release rates from sediment cores indicate that Lost Bay may be one of several areas that may be contributing substantially to internal loading. Internal loading is a concern because nutrients may cause excessive algal growth including potentially toxic cyanobacteria. The cyanobacterial hepatotoxin, microcystin, was detected in 7 of 14 cyanobacterial bloom samples, with total concentrations exceeding 1.0 microgram per liter, the World Health Organization's guideline for finished drinking water for the congener, microcystin-LR. Comparisons of the results of this study to previous studies indicate that chlorophyll-a concentrations and trophic state indices have improved since 2000, when the rules governing dam operation changed. However, total-phosphorus concentrations have not changed significantly since 2000.

  6. The nutrient load from food waste generated onboard ships in the Baltic Sea.

    Science.gov (United States)

    Wilewska-Bien, Magda; Granhag, Lena; Andersson, Karin

    2016-04-15

    The combination of the sensitive characteristics of the Baltic Sea and the intense maritime traffic makes the marine environment vulnerable to anthropogenic influences. The theoretical scenario calculated in this study shows that the annually generated food waste onboard ships in traffic in the Baltic Sea contains about 182tonnes of nitrogen and 34tonnes of phosphorus. Today, all food waste generated onboard can be legally discharged into the marine environment at a distance of 12NM from the nearest land. The annual load of nitrogen contained in the food waste corresponds to 52% of load of nitrogen from the ship-generated sewage. Future regulations for sewage discharge in the Baltic Sea will require significant reduction of total nitrogen and phosphorus released. The contribution of nutrients from food waste compared to sewage will therefore be relatively larger in the future, if food waste still can be legally discharged. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. Surf or Turf: How shifting from animal feed to food production could reduce nutrient loading to the Gulf of Mexico

    Science.gov (United States)

    Donner, S. D.

    2004-12-01

    The use of nitrogen fertilizers on croplands in central U.S. is commonly blamed for the increase in nitrogen export by the Mississippi River since the 1950s and the emergence of the large seasonal hypoxic zone in the Gulf of Mexico. The majority of production of the major Mississippi Basin crops like corn and soybean is currently used as animal feed rather than directly for human food. This study uses U.S. Department of Agriculture inventory data and nutrient cycling models to investigate how replacing the meat protein produced from Mississippi croplands with vegetable protein would affect nutrient inputs to Mississippi Basin and nitrogen loading to the Gulf of Mexico. The results show that a shift to only vegetable, dairy and some poultry production from Mississippi Basin croplands could produce the same amount of dietary protein with less than half the current land and nutrient demands. These changes would reduce the annual export of nitrate-nitrogen by the Mississippi River to a consistently low level at which hypoxic zone in the Gulf of Mexico has historically been small or non-existent.

  8. Estimation of Tile Drainage Contribution to Streamflow and Nutrient Export Loads

    Science.gov (United States)

    Schilling, K. E.; Arenas Amado, A.; Jones, C. S.; Weber, L. J.

    2015-12-01

    Subsurface drainage is a very common practice in the agricultural U.S. Midwest. It is typically installed in poorly drained soils in order to enhance crop yields. The presence of tile drains creates a route for agrichemicals to travel and therefore negatively impacts stream water quality. This study estimated through end-member analyses the contributions of tile drainage, groundwater, and surface runoff to streamflow at the watershed scale based on continuously monitored data. Especial attention was devoted to quantifying tile drainage impact on watershed streamflow and nutrient export loads. Data analyzed includes streamflow, rainfall, soil moisture, shallow groundwater levels, in-stream nitrate+nitrite concentrations and specific conductance. Data were collected at a HUC12 watershed located in Northeast Iowa, USA. Approximately 60% of the total watershed area is devoted to agricultural activities and forest and grassland are the other two predominant land uses. Results show that approximately 20% of total annual streamflow comes from tile drainage and during rainfall events tile drainage contribution can go up to 30%. Furthermore, for most of the analyzed rainfall events groundwater responded faster and in a more dramatic fashion than tile drainage. The State of Iowa is currently carrying out a plan to reduce nutrients in Iowa waters and the Gulf of Mexico (Iowa Nutrient Reduction Strategy). The outcome of this investigation has the potential to assist in Best Management Practice (BMP) scenario selection and therefore help the state achieve water quality goals.

  9. Spatial modeling on the nutrient retention of an estuary wetland

    NARCIS (Netherlands)

    Li, X.; Xiao, D.; Jongman, R.H.G.; Harms, W.B.; Bregt, A.K.

    2003-01-01

    There is a great potential to use the estuary wetland as a final filter for nutrient enriched river water, and reduce the possibility of coastal water eutrophication. Based upon field data, spatial models were designed on a stepwise basis to simulate the nutrient reduction function of the wetland in

  10. Solving Nutrient Loading in the Great Lakes: An Integrative, Interdisciplinary and Ambidextrous Approach

    Science.gov (United States)

    Borrello, M. C.; Keeton, T.; Foley, T.; Frost, A.; Green, N.; Isler, J.

    2014-12-01

    Environmental impacts from industrialized agriculture have been studied extensively over the past two decades. Degradation of surface water occurs, primarily as a result of nutrient loading, causing algal blooms in streams and lakes. Discovery of the toxin microcystin in Lake Erie, a drinking water source for some municipalities, has been associated with agricultural runoff and created a new awareness in the general public. This study used data gathered over ten years by local residents, high school students and undergraduates on surface water around the Lower Peninsula of Michigan to test a simple correlation of nutrients (soluble reactive phosphorus and nitrogen ammonia) along with the presence of specific antibiotics and antibiotic resistance to identify dominant sources of nutrient loading in the Lake Huron Watershed. Data gathering came from multiple sources and were processed by faculty and students at an undergraduate, liberal arts institution. College students from various disciplines worked with community members and municipalities in an effort to describe the problem. Students proposed solutions which by-passed relatively inactive regulatory agencies to create an integrative, interactive resolution that involved a surprisingly wide extent of the community. Addressing cultural norms beginning with those most affected by a degraded environment has reaped some success in changing behavior and moving towards a sustainable solution. The research conducted and supervised by undergraduate students has significance in the broader, professional area of geochemistry, environmental health and sustainable agriculture. That fact plays an important role in how the students see themselves in the process and what motivated them to: 1. Choose to participate in the research in the first place, 2. Reach out to the broader community (scientific and regional) to carry out their research and 3. Pursue solutions beyond the classroom and summer research experience.

  11. Evergreen shrub traits and peatland carbon cycling under high nutrient load

    Science.gov (United States)

    Larmola, Tuula; Bui, Vi; Bubier, Jill L.; Wang, Meng; Murphy, Meaghan; Moore, Tim R.

    2016-04-01

    The reactive nitrogen (N) assimilated by plants is usually invested in chlorophyll to improve light harvesting capacity and in soluble proteins such as Rubisco to enhance carbon (C) assimilation. We studied the effects of simulated atmospheric N deposition on different traits of two evergreen shrubs Chamaedaphne calyculata and Rhododendron groenlandicum in a nutrient-poor Mer Bleue Bog, Canada that has been fertilized with N as NO3 and NH4 (2-8 times ambient annual wet deposition) with or without phosphorus (P) and potassium (K) for 7-12 years. We examined how nutrient addition influences the plant performance at leaf and canopy level and linked the trait responses with ecosystem C cycling. At the leaf level, we measured physiological and biochemical traits: CO2 exchange and chlorophyll fluorescence, an indicator of plant stress in terms of light harvesting capacity; and to study changes in photosynthetic nutrient use efficiency, we also determined the foliar chlorophyll, N, and P contents. At the canopy level, we examined morphological and phenological traits: growth responses and leaf longevity during two growing seasons. Regardless of treatment, the majority of leaves showed no signs of stress in terms of light harvesting capacity. The plants were N saturated: with increasing foliar N content, the higher proportion of N was not used in photosynthesis. Foliar net CO2 assimilation rates did not differ significantly among treatments, but the additions of N, P, and K together resulted in higher respiration rates. The analysis of the leaf and canopy traits showed that the two shrubs had different strategies: C. calyculata was more responsive to nutrient additions, more deciduous-like, whereas R. groenlandicum maintained evergreen features under nutrient load, shedding its leaves even later in the season. In all, simulated atmospheric N deposition did not benefit the photosynthetic apparatus of the dominant shrubs, but resulted in higher foliar respiration

  12. Modeling of Generic Slung Load System

    DEFF Research Database (Denmark)

    Bisgaard, Morten; Bendtsen, Jan Dimon; la Cour-Harbo, Anders

    2009-01-01

    ' Principle of Least Constraint using the Udwadia-Kalaba equation and can be used to model all body to body slung load suspension types. The model provides intuitive and easy-to-use means of modelling and simulating different slung load suspension types. It includes detection of, and response to, wire...... of the model is illustrated through simulations and flight verifications.  ...

  13. The MARINA model (Model to Assess River Inputs of Nutrients to seAs)

    OpenAIRE

    Strokal, Maryna; Kroeze, Carolien; Wang, Mengru; Bai, Zhaohai; Ma, Lin

    2016-01-01

    Chinese agriculture has been developing fast towards industrial food production systems that discharge nutrient-rich wastewater into rivers. As a result, nutrient export by rivers has been increasing, resulting in coastal water pollution. We developed a Model to Assess River Inputs of Nutrients to seAs (MARINA) for China. The MARINA Nutrient Model quantifies river export of nutrients by source at the sub-basin scale as a function of human activities on land. MARINA is a downscaled version for...

  14. Epiphyte load on the seagrass Posidonia oceanica (L. Delile does not indicate anthropogenic nutrient loading in Cabrera Archipelago National Park (Balearic Islands, Western Mediterranean

    Directory of Open Access Journals (Sweden)

    Jorge Terrados

    2008-09-01

    Full Text Available The epiphyte load on the leaves of the seagrass Posidonia oceanica (L. Delile was estimated at the end of summer in three sites and two depths (7 m and 17 m of the Cabrera Archipelago National Park (Balearic Islands, Western Mediterranean from 2004 to 2006 to evaluate if epiphyte load could be used as an indicator of anthropogenic nutrient loading in the shallow marine ecosystems of the park. Asymmetrical ANOVA was used to divide data variability into two components: the contrast between the site receiving direct anthropogenic inputs of nutrients and organic matter (Es Port and the two control sites (Cala Santa María, Es Burri; and the variability between the control sites. The nitrogen concentration in P. oceanica leaves was higher in Es Port than in Cala Santa María and Es Burri but only at 7 m depth. There was no difference between the epiphyte load on P. oceanica shoots in Es Port and the sites without inputs at both 7 m and 17 m. However, the epiphyte load in Es Burri was higher than that in Cala Santa María at both depths. The results show that the epiphyte load on P. oceanica shoots was not a sensitive indicator of anthropogenic nutrient and organic matter loading in Cabrera Archipelago National Park.

  15. Soil and Water Assessment Tool (SWAT) Applicability on Nutrients Loadings Prediction in Mountainous Lower Bear Malad River (LBMR) Watershed, Utah.

    Science.gov (United States)

    Salha, A. A.; Stevens, D. K.

    2014-12-01

    The application of watershed simulation models is indispensable when pollution is generated by a nonpoint source. These models should be able to simulate large complex watersheds with varying soils, land use and management conditions over long periods of time. This study presents the application of Soil and Water Assessment Tool (SWAT) to investigate, manage, and research the transport and fate of nutrients in (Subbasin HUC 16010204) Lower Bear Malad River (LBMR) watershed, Box elder County, Utah. Water quality problems arise primarily from high phosphorus and total suspended sediment concentrations that were caused by increasing agricultural and farming activities and complex network of canals and ducts of varying sizes and carrying capacities that transport water (for farming and agriculture uses). Using the available input data (Digital Elevation Model (DEM), land use/Land cover (LULC), soil map and weather and climate data for 20 years (1990-2010) to predict the water quantity and quality of the LBMR watershed using a spatially distributed model version of hydrological ArcSWAT model (ArcSWAT 2012.10_1.14). No previous studies have been found in the literature regarding an in-depth simulation study of the Lower Bear Malad River (LBMR) watershed to simulate stream flow and to quantify the associated movement of nitrogen, phosphorus, and sediment. It is expected that the model mainly will predict monthly mean total phosphorus (TP) concentration and loadings in a mountainous LBRM watershed (steep Wellsville mountain range with peak of (2,857 m)) having into consideration the snow and runoff variables affecting the prediction process. The simulated nutrient concentrations were properly consistent with observations based on the R2 and Nash- Sutcliffe fitness factors. Further, the model will be able to manage and assess the land application in that area with corresponding to proper BMPs regarding water quality management. Keywords: Water Quality Modeling; Soil and

  16. Modeling nutrient in-stream processes at the watershed scale using Nutrient Spiralling metrics

    Science.gov (United States)

    Marcé, R.; Armengol, J.

    2009-07-01

    One of the fundamental problems of using large-scale biogeochemical models is the uncertainty involved in aggregating the components of fine-scale deterministic models in watershed applications, and in extrapolating the results of field-scale measurements to larger spatial scales. Although spatial or temporal lumping may reduce the problem, information obtained during fine-scale research may not apply to lumped categories. Thus, the use of knowledge gained through fine-scale studies to predict coarse-scale phenomena is not straightforward. In this study, we used the nutrient uptake metrics defined in the Nutrient Spiralling concept to formulate the equations governing total phosphorus in-stream fate in a deterministic, watershed-scale biogeochemical model. Once the model was calibrated, fitted phosphorus retention metrics where put in context of global patterns of phosphorus retention variability. For this purpose, we calculated power regressions between phosphorus retention metrics, streamflow, and phosphorus concentration in water using published data from 66 streams worldwide, including both pristine and nutrient enriched streams. Performance of the calibrated model confirmed that the Nutrient Spiralling formulation is a convenient simplification of the biogeochemical transformations involved in total phosphorus in-stream fate. Thus, this approach may be helpful even for customary deterministic applications working at short time steps. The calibrated phosphorus retention metrics were comparable to field estimates from the study watershed, and showed high coherence with global patterns of retention metrics from streams of the world. In this sense, the fitted phosphorus retention metrics were similar to field values measured in other nutrient enriched streams. Analysis of the bibliographical data supports the view that nutrient enriched streams have lower phosphorus retention efficiency than pristine streams, and that this efficiency loss is maintained in a wide

  17. Modeling nutrient in-stream processes at the watershed scale using Nutrient Spiralling metrics

    Directory of Open Access Journals (Sweden)

    J. Armengol

    2009-07-01

    Full Text Available One of the fundamental problems of using large-scale biogeochemical models is the uncertainty involved in aggregating the components of fine-scale deterministic models in watershed applications, and in extrapolating the results of field-scale measurements to larger spatial scales. Although spatial or temporal lumping may reduce the problem, information obtained during fine-scale research may not apply to lumped categories. Thus, the use of knowledge gained through fine-scale studies to predict coarse-scale phenomena is not straightforward. In this study, we used the nutrient uptake metrics defined in the Nutrient Spiralling concept to formulate the equations governing total phosphorus in-stream fate in a deterministic, watershed-scale biogeochemical model. Once the model was calibrated, fitted phosphorus retention metrics where put in context of global patterns of phosphorus retention variability. For this purpose, we calculated power regressions between phosphorus retention metrics, streamflow, and phosphorus concentration in water using published data from 66 streams worldwide, including both pristine and nutrient enriched streams.
    Performance of the calibrated model confirmed that the Nutrient Spiralling formulation is a convenient simplification of the biogeochemical transformations involved in total phosphorus in-stream fate. Thus, this approach may be helpful even for customary deterministic applications working at short time steps. The calibrated phosphorus retention metrics were comparable to field estimates from the study watershed, and showed high coherence with global patterns of retention metrics from streams of the world. In this sense, the fitted phosphorus retention metrics were similar to field values measured in other nutrient enriched streams. Analysis of the bibliographical data supports the view that nutrient enriched streams have lower phosphorus retention efficiency than pristine streams, and that this efficiency loss

  18. Effect of Nutrient Management Planning on Crop Yield, Nitrate Leaching and Sediment Loading in Thomas Brook Watershed

    Science.gov (United States)

    Amon-Armah, Frederick; Yiridoe, Emmanuel K.; Ahmad, Nafees H. M.; Hebb, Dale; Jamieson, Rob; Burton, David; Madani, Ali

    2013-11-01

    Government priorities on provincial Nutrient Management Planning (NMP) programs include improving the program effectiveness for environmental quality protection, and promoting more widespread adoption. Understanding the effect of NMP on both crop yield and key water-quality parameters in agricultural watersheds requires a comprehensive evaluation that takes into consideration important NMP attributes and location-specific farming conditions. This study applied the Soil and Water Assessment Tool (SWAT) to investigate the effects of crop and rotation sequence, tillage type, and nutrient N application rate on crop yield and the associated groundwater leaching and sediment loss. The SWAT model was applied to the Thomas Brook Watershed, located in the most intensively managed agricultural region of Nova Scotia, Canada. Cropping systems evaluated included seven fertilizer application rates and two tillage systems (i.e., conventional tillage and no-till). The analysis reflected cropping systems commonly managed by farmers in the Annapolis Valley region, including grain corn-based and potato-based cropping systems, and a vegetable-horticulture system. ANOVA models were developed and used to assess the effects of crop management choices on crop yield and two water-quality parameters (i.e., leaching and sediment loading). Results suggest that existing recommended N-fertilizer rate can be reduced by 10-25 %, for grain crop production, to significantly lower leaching ( P > 0.05) while optimizing the crop yield. The analysis identified the nutrient N rates in combination with specific crops and rotation systems that can be used to manage leaching while balancing impacts on crop yields within the watershed.

  19. Effects of nutrient loading on the carbon balance of coastal wetland sediments

    Science.gov (United States)

    Morris, J.T.; Bradley, P.M.

    1999-01-01

    Results of a 12-yr study in an oligotrophic South Carolina salt marsh demonstrate that soil respiration increased by 795 g C m-2 yr-1 and that carbon inventories decreased in sediments fertilized with nitrogen and phosphorus. Fertilized plots became net sources of carbon to the atmosphere, and sediment respiration continues in these plots at an accelerated pace. After 12 yr of treatment, soil macroorganic matter in the top 5 cm of sediment was 475 g C m-2 lower in fertilized plots than in controls, which is equivalent to a constant loss rate of 40 g C m-2 yr-1. It is not known whether soil carbon in fertilized plots has reached a new equilibrium or continues to decline. The increase in soil respiration in the fertilized plots was far greater than the loss of sediment organic matter, which indicates that the increase in soil respiration was largely due to an increase in primary production. Sediment respiration in laboratory incubations also demonstrated positive effects of nutrients. Thus, the results indicate that increased nutrient loading of oligotrophic wetlands can lead to an increased rate of sediment carbon turnover and a net loss of carbon from sediments.

  20. A dynamic growth model for prediction of nutrient partitioning and manure production in growing–finishing pigs: Model development and evaluation

    DEFF Research Database (Denmark)

    Danfær, Allan Christian; Jørgensen, Henry; Kebreab, E

    2015-01-01

    trials using growing–finishing pig diets that had a wide range of nutrient chemical composition. Nutrient and water excretion were quantified using the principle of mass conservation. The average daily observed and predicted manure production was 3.79 and 3.99 kg/d, respectively, with a RMSPE of 0.49 kg......Nutrient loading and air emissions from swine operations raise environmental concerns. The objective of the study was to describe and evaluate a mathematical model (Davis Swine Model) of nutrient partitioning and predict manure excretion and composition on a daily basis. State variables...... the body constituent pools. It was assumed that fluxes of metabolites follow saturation kinetics, depending on metabolite concentrations. The main inputs to the model were diet nutrient composition, feed intake, water-to-feed ratio, and initial BW. First, the model was challenged with nutrient partitioning...

  1. Including spatial data in nutrient balance modelling on dairy farms

    Science.gov (United States)

    van Leeuwen, Maricke; van Middelaar, Corina; Stoof, Cathelijne; Oenema, Jouke; Stoorvogel, Jetse; de Boer, Imke

    2017-04-01

    The Annual Nutrient Cycle Assessment (ANCA) calculates the nitrogen (N) and phosphorus (P) balance at a dairy farm, while taking into account the subsequent nutrient cycles of the herd, manure, soil and crop components. Since January 2016, Dutch dairy farmers are required to use ANCA in order to increase understanding of nutrient flows and to minimize nutrient losses to the environment. A nutrient balance calculates the difference between nutrient inputs and outputs. Nutrients enter the farm via purchased feed, fertilizers, deposition and fixation by legumes (nitrogen), and leave the farm via milk, livestock, manure, and roughages. A positive balance indicates to which extent N and/or P are lost to the environment via gaseous emissions (N), leaching, run-off and accumulation in soil. A negative balance indicates that N and/or P are depleted from soil. ANCA was designed to calculate average nutrient flows on farm level (for the herd, manure, soil and crop components). ANCA was not designed to perform calculations of nutrient flows at the field level, as it uses averaged nutrient inputs and outputs across all fields, and it does not include field specific soil characteristics. Land management decisions, however, such as the level of N and P application, are typically taken at the field level given the specific crop and soil characteristics. Therefore the information that ANCA provides is likely not sufficient to support farmers' decisions on land management to minimize nutrient losses to the environment. This is particularly a problem when land management and soils vary between fields. For an accurate estimate of nutrient flows in a given farming system that can be used to optimize land management, the spatial scale of nutrient inputs and outputs (and thus the effect of land management and soil variation) could be essential. Our aim was to determine the effect of the spatial scale of nutrient inputs and outputs on modelled nutrient flows and nutrient use efficiencies

  2. Protecting the Green Behind the Gold: Catchment-Wide Restoration Efforts Necessary to Achieve Nutrient and Sediment Load Reduction Targets in Gold Coast City, Australia

    Science.gov (United States)

    Waltham, Nathan J.; Barry, Michael; McAlister, Tony; Weber, Tony; Groth, Dominic

    2014-10-01

    The Gold Coast City is the tourist center of Australia and has undergone rapid and massive urban expansion over the past few decades. The Broadwater estuary, in the heart of the City, not only offers an array of ecosystems services for many important aquatic wildlife species, but also supports the livelihood and lifestyles of residents. Not surprisingly, there have been signs of imbalance between these two major services. This study combined a waterway hydraulic and pollutant transport model to simulate diffuse nutrient and sediment loads under past and future proposed land-use changes. A series of catchment restoration initiatives were modeled in an attempt to define optimal catchment scale restoration efforts necessary to protect and enhance the City's waterways. The modeling revealed that for future proposed development, a business as usual approach to catchment management will not reduce nutrient and sediment loading sufficiently to protect the community values. Considerable restoration of upper catchment tributaries is imperative, combined with treatment of stormwater flow from intensively developed sub-catchment areas. Collectively, initiatives undertaken by regulatory authorities to date have successfully reduced nutrient and sediment loading reaching adjoining waterways, although these programs have been ad hoc without strategic systematic planning and vision. Future conservation requires integration of multidisciplinary science and proactive management driven by the high ecological, economical, and community values placed on the City's waterways. Long-term catchment restoration and conservation planning requires an extensive budget (including political and societal support) to handle ongoing maintenance issues associated with scale of restoration determined here.

  3. Final Project Report Load Modeling Transmission Research

    Energy Technology Data Exchange (ETDEWEB)

    Lesieutre, Bernard [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Bravo, Richard [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Yinger, Robert [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Chassin, Dave [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Huang, Henry [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Lu, Ning [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Hiskens, Ian [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Venkataramanan, Giri [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2012-03-31

    The research presented in this report primarily focuses on improving power system load models to better represent their impact on system behavior. The previous standard load model fails to capture the delayed voltage recovery events that are observed in the Southwest and elsewhere. These events are attributed to stalled air conditioner units after a fault. To gain a better understanding of their role in these events and to guide modeling efforts, typical air conditioner units were testing in laboratories. Using data obtained from these extensive tests, new load models were developed to match air conditioner behavior. An air conditioner model is incorporated in the new WECC composite load model. These models are used in dynamic studies of the West and can impact power transfer limits for California. Unit-level and systemlevel solutions are proposed as potential solutions to the delayed voltage recovery problem.

  4. A dual porosity model of nutrient uptake by root hairs

    KAUST Repository

    Zygalakis, K. C.

    2011-08-09

    Summary: • The importance of root hairs in the uptake of sparingly soluble nutrients is understood qualitatively, but not quantitatively, and this limits efforts to breed plants tolerant of nutrient-deficient soils. • Here, we develop a mathematical model of nutrient uptake by root hairs allowing for hair geometry and the details of nutrient transport through soil, including diffusion within and between soil particles. We give illustrative results for phosphate uptake. • Compared with conventional \\'single porosity\\' models, this \\'dual porosity\\' model predicts greater root uptake because more nutrient is available by slow release from within soil particles. Also the effect of soil moisture is less important with the dual porosity model because the effective volume available for diffusion in the soil is larger, and the predicted effects of hair length and density are different. • Consistent with experimental observations, with the dual porosity model, increases in hair length give greater increases in uptake than increases in hair density per unit main root length. The effect of hair density is less in dry soil because the minimum concentration in solution for net influx is reached more rapidly. The effect of hair length is much less sensitive to soil moisture. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.

  5. Wetland management reduces sediment and nutrient loading to the upper Mississippi River

    Science.gov (United States)

    Kreiling, Rebecca M.; Schubauer-Berigan, Joseph P.; Richardson, William B.; Bartsch, Lynn; Hughes, Peter E.; Strauss, Eric A.

    2013-01-01

    Restored riparian wetlands in the Upper Mississippi River basin have potential to remove sediment and nutrients from tributaries before they flow into the Mississippi River. For 3 yr we calculated retention efficiencies of a marsh complex, which consisted of a restored marsh and an adjacent natural marsh that were connected to Halfway Creek, a small tributary of the Mississippi. We measured sediment, N, and P removal through a mass balance budget approach, N removal through denitrification, and N and P removal through mechanical soil excavation. The marsh complex had average retention rates of approximately 30 Mg sediment ha−1 yr−1, 26 kg total N ha−1 yr−1, and 20 kg total P ha−1 yr−1. Water flowed into the restored marsh only during high-discharge events. Although the majority of retention occurred in the natural marsh, portions of the natural marsh were hydrologically disconnected at low discharge due to historical over-bank sedimentation. The natural marsh removed >60% of sediment, >10% of P, and >5% of N loads (except the first year, when it was a N source). The marsh complex was a source of NH4+ and soluble reactive P. The average denitrification rate for the marsh complex was 2.88 mg N m−2 h−1. Soil excavation removed 3600 Mg of sediment, 5.6 Mg of N, and 2.7 Mg of P from the restored marsh. The marsh complex was effective in removing sediment and nutrients from storm flows; however, retention could be increased if more water was diverted into both restored and natural marshes before entering the river.

  6. Use of linear programming models in experimentation with plant nutrients

    Directory of Open Access Journals (Sweden)

    Mauro Brino Garcia

    2013-06-01

    Full Text Available Nutrition is an important issue of plant cultivation and experimentation with plant nutrients is a supporting tool for agriculture. However, use of high purity grade reagents as nutrient sources can be expensive and increases the cost of an experiment. The objective of this study was to minimize the acquisition cost of high purity grade reagents in experiments on plant nutrient deficiency by using the missing element technique through linear programming models, and to generate recommendation tables for preparation of culture solutions, as well as to quantify gains through a simulated experiment. Two linear programming models were formulated containing concentration constraints for each nutrient in the culture solution. Model A was based on 16 reagents for preparation of the culture solution, while model B was based on 27 reagents, looking to increase choice options. Results showed that both models minimized the acquisition cost of reagents, allowing a 9.03% reduction in model A and a 25.98% reduction in model B. The missing sulfur treatment proved the most costly for reagent acquisition while the missing nitrogen treatment proved the least costly. It was concluded that the formulated models were capable of reducing acquisition costs of reagents, yet the recommendations generated by them should be tested and checked for practical viability.

  7. AN ECOSYSTEM MODEL OF FISHERIES AND NUTRIENT ENRICHMENT

    DEFF Research Database (Denmark)

    Nguyen, Thanh Viet; Vestergaard, Niels

    2009-01-01

      Economic models of fishery largely ignore the linkages to lower trophic levels. In particular, environmental data and other bottom-up information is widely disregarded. Nor are changes in physical environment (bottom-up) alongside both exogenous and endogenous environmental effects included...... in the general ecosystem models. The objectives of this paper are modeling the impacts of nutrient enrichment on fisheries; particularly the impacts on consumer stocks and the fisheries based on these stocks are presented. We consider an aquatic ecosystem with four components: producers (autotrophs), consumers...... (herbivores, carnivores), nonliving matter and pollution sources. The interactions between nutrients-producers, producers- consumers are assumed following the Holling type II functional response. Pollution sources cause excess nutrients which linked to increase primary productivity, hypoxia and anoxia...

  8. Soil Nutrient Stocks in Sub-Saharan Africa: Modeling Soil Nutrients Using Machine Learning

    Science.gov (United States)

    Cooper, M. W.; Hengl, T.; Shepherd, K.; Heuvelink, G. B. M.

    2017-12-01

    We present the results of our work modeling 15 target soil nutrients at 250 meter resolution across Sub-Saharan Africa. We used a large stack of GIS layers as covariates, including layers on topography, climate, geology, hydrology and land cover. As training data we used ca. 59,000 soil samples harmonized across a number of projects and datasets, and we modeled each nutrient using an ensemble of random forest and gradient boosting algorithms, implemented using the R packages ranger and xgboost. Using cross validation, we determined that significant models can be produced for organic Carbon, total (organic) Nitrogen, total Phosphorus, and extractable Phosphorous, Potassium, Calcium, Magnesium, Sulfur, Sodium, Iron, Manganese, Zinc, Copper, Aluminum and Boron, with an R-square value between 40 and 95%. The main covariates explaining spatial distribution of nutrients were precipitation and land form parameters. However, we were unable to significantly predict Sulfur, Phosphorus and Boron as these could not be correlated with any environmental covariates we used. Although the accuracy of predictions looks promising, our predictions likely suffer from the significant spatial clustering of the sampling locations, as well as a lack of more detailed data on geology and parent material at a continental scale. These results will contribute to targeting agricultural investments and interventions, as well as targeting restoration efforts and estimating yield potential and yield gaps. These results were recently published in the journal Nutrient Cycling in Agroecosystems (DOI: 10.1007/s10705-017-9870-x) and the maps are available for download under the ODC Open Database License.

  9. Fiber Bundle Model Under Heterogeneous Loading

    Science.gov (United States)

    Roy, Subhadeep; Goswami, Sanchari

    2018-03-01

    The present work deals with the behavior of fiber bundle model under heterogeneous loading condition. The model is explored both in the mean-field limit as well as with local stress concentration. In the mean field limit, the failure abruptness decreases with increasing order k of heterogeneous loading. In this limit, a brittle to quasi-brittle transition is observed at a particular strength of disorder which changes with k. On the other hand, the model is hardly affected by such heterogeneity in the limit where local stress concentration plays a crucial role. The continuous limit of the heterogeneous loading is also studied and discussed in this paper. Some of the important results related to fiber bundle model are reviewed and their responses to our new scheme of heterogeneous loading are studied in details. Our findings are universal with respect to the nature of the threshold distribution adopted to assign strength to an individual fiber.

  10. Modelling and Simulation of Wave Loads

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Thoft-Christensen, Palle

    1985-01-01

    A simple model of the wave load on stender members of offshore structures is described . The wave elevation of the sea stateis modelled by a stationary Gaussian process. A new procedure to simulate realizations of the wave loads is developed. The simulation method assumes that the wave particle...... velocity can be approximated by a Gaussian Markov process. Known approximate results for the first passage density or equivalently, the distribution of the extremes of wave loads are presented and compared with rather precise simulation results. It is demonstrated that the approximate results...

  11. Modelling and Simulation of Wave Loads

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Thoft-Christensen, Palle

    velocity can be approximated by a Gaussian Markov process. Known approximate results for the first-passage density or equivalently, the distribution of the extremes of wave loads are presented and compared with rather precise simulation results. It is demonstrated that the approximate results......A simple model of the wave load on slender members of offshore structures is described. The wave elevation of the sea state is modelled by a stationary Gaussian process. A new procedure to simulate realizations of the wave loads is developed. The simulation method assumes that the wave particle...

  12. Modelling and Simulation of Wave Loads

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Thoft-Christensen, Palle

    1985-01-01

    velocity can be approximated by a Gaussian Markov process. Known approximate results for the first passage density or equivalently, the distribution of the extremes of wave loads are presented and compared with rather precise simulation results. It is demonstrated that the approximate results......A simple model of the wave load on stender members of offshore structures is described . The wave elevation of the sea stateis modelled by a stationary Gaussian process. A new procedure to simulate realizations of the wave loads is developed. The simulation method assumes that the wave particle...

  13. Competitive interactions between native Spartina alterniflora and non-native Phragmites australis depend on nutrient loading and temperature.

    Directory of Open Access Journals (Sweden)

    Rene Legault

    Full Text Available We explored the nature and impact of competitive interactions between the salt marsh foundational plant Spartina alterniflora and invasive Phragmites australis in New England under varying levels of anthropogenic influence from nutrient loading and temperature warming. Plants were grown with and without competition in mesocosms over a four-month growing season. Mesocosms were split evenly among three levels of nutrient additions and two temperatures varying by an average of ~3° C, manipulated using small greenhouses. We measured aboveground productivity as total biomass, numbers of new stems, and mean stem height. Nutrient enrichment increased all growth parameters, while competition generally reduced aboveground biomass and the production of new stems in both species. Most importantly, smooth cordgrass suffered no negative consequences of competition when no nutrients were added and temperature was elevated. The results of this study suggest that minimizing nutrient loading into coastal marshes could be an important factor in slowing the spread of common reed into the low marsh zone of New England salt marshes as global temperatures continue to warm.

  14. The MARINA model (Model to Assess River Inputs of Nutrients to seAs)

    NARCIS (Netherlands)

    Strokal, Maryna; Kroeze, Carolien; Wang, Mengru; Bai, Zhaohai; Ma, Lin

    2016-01-01

    Chinese agriculture has been developing fast towards industrial food production systems that discharge nutrient-rich wastewater into rivers. As a result, nutrient export by rivers has been increasing, resulting in coastal water pollution. We developed a Model to Assess River Inputs of Nutrients

  15. Modeling farm nutrient flows in the North China Plain to reduce nutrient losses

    NARCIS (Netherlands)

    Zhao, Zhanqing; Bai, Zhaohai; Wei, Sha; Ma, Wenqi; Wang, Mengru; Kroeze, Carolien; Ma, Lin

    2017-01-01

    Years of poor nutrient management practices in the agriculture industry in the North China Plain have led to large losses of nutrients to the environment, causing severe ecological consequences. Analyzing farm nutrient flows is urgently needed in order to reduce nutrient losses. A farm-level

  16. Multiple stressor effects on marine infauna: responses of estuarine taxa and functional traits to sedimentation, nutrient and metal loading

    KAUST Repository

    Ellis, Joanne

    2017-09-14

    Sedimentation, nutrients and metal loading to coastal environments are increasing, associated with urbanization and global warming, hence there is a growing need to predict ecological responses to such change. Using a regression technique we predicted how maximum abundance of 20 macrobenthic taxa and 22 functional traits separately and interactively responded to these key stressors. The abundance of most taxa declined in response to sedimentation and metal loading while a unimodal response was often associated with nutrient loading. Optimum abundances for both taxa and traits occurred at relatively low stressor levels, highlighting the vulnerability of estuaries to increasing stressor loads. Individual taxa were more susceptible to stress than traits, suggesting that functional traits may be less sensitive for detecting changes in ecosystem health. Multiplicative effects were more common than additive interactions. The observed sensitivity of most taxa to increasing sedimentation and metal loading and the documented interaction effects between multiple stressors have important implications for understanding and managing the ecological consequences of eutrophication, sedimentation and contaminants on coastal ecosystems.

  17. Modelling nutrient cycling in forest ecosystems; Modellering av naeringssyklus i skogoekosystemer

    Energy Technology Data Exchange (ETDEWEB)

    Kvindesland, Sheila H.S.B.

    1997-12-31

    Acid deposition`s threat to fresh water and forest environments became an issue in the late 1960s. Acid deposition and forest nutrient cycling then began to be researched in greater co-operation. This thesis studies nutrient cycling processes in Norway spruce forests, emphasizing the effects on soil chemical properties, soil solution chemistry and streamwater chemistry. It investigates the effects of different aged stands on nutrient cycling and sets up nutrient budgets of the base cations and nitrogen at two sites in Norway. It also selects, documents, calibrates, tests and improves nutrient cycling models for use in Norwegian forests. 84 refs., 44 figs., 46 tabs.

  18. Modeling Antibiotic Tolerance in Biofilms by Accounting for Nutrient Limitation

    OpenAIRE

    Roberts, Mark E.; Stewart, Philip S.

    2004-01-01

    A mathematical model of biofilm dynamics was used to investigate the protection from antibiotic killing that can be afforded to microorganisms in biofilms based on a mechanism of localized nutrient limitation and slow growth. The model assumed that the rate of killing by the antibiotic was directly proportional to the local growth rate. Growth rates in the biofilm were calculated by using the local concentration of a single growth-limiting substrate with Monod kinetics. The concentration prof...

  19. Nutrient Load of the Sakumo Lagoon at the Sakumo Ramsar Site in ...

    African Journals Online (AJOL)

    Environmental Protection Agency (EPA)-Ghana permissible guideline values for effluents discharged into water bodies and values from similar studies on the lagoon in 1995 and 2003. Observations showed that, of all the nutrients studied, phosphates were the highest in the Sakumo lagoon. The decreasing order of nutrient ...

  20. Effects of salinity and nutrient load and their interaction on Zostera marina

    NARCIS (Netherlands)

    Van Katwijk, M.; Schmitz, G.; Gasseling, A.P.; Van Avesaath, P.H.

    1999-01-01

    Generally, seagrass Zostera marina L. distribution in the Wadden Sea and south-west Netherlands is Limited to waters with low to moderate nutrient concentrations. However, it is known that Z. marina also occurs at high nutrient concentrations when growing in low salinity environments. In this study,

  1. Modeling investigation of the nutrient and phytoplankton variability in the Chesapeake Bay outflow plume

    Science.gov (United States)

    Jiang, Long; Xia, Meng

    2018-03-01

    The Chesapeake Bay outflow plume (CBOP) is the mixing zone between Chesapeake Bay and less eutrophic continental shelf waters. Variations in phytoplankton distribution in the CBOP are critical to the fish nursery habitat quality and ecosystem health; thus, an existing hydrodynamic-biogeochemical model for the bay and the adjacent coastal ocean was applied to understand the nutrient and phytoplankton variability in the plume and the dominant environmental drivers. The simulated nutrient and chlorophyll a distribution agreed well with field data and real-time satellite imagery. Based on the model calculation, the net dissolved inorganic nitrogen (DIN) and phosphorus (DIP) flux at the bay mouth was seaward and landward during 2003-2012, respectively. The CBOP was mostly nitrogen-limited because of the relatively low estuarine DIN export. The highest simulated phytoplankton biomass generally occurred in spring in the near field of the plume. Streamflow variations could regulate the estuarine residence time, and thus modulate nutrient export and phytoplankton biomass in the plume area; in comparison, changing nutrient loading with fixed streamflow had a less extensive impact, especially in the offshore and far-field regions. Correlation analyses and numerical experiments revealed that southerly winds on the shelf were effective in promoting the offshore plume expansion and phytoplankton accumulation. Climate change including precipitation and wind pattern shifts is likely to complicate the driving mechanisms of phytoplankton variability in the plume region.

  2. AN ECOSYSTEM MODEL OF FISHERIES AND NUTRIENT ENRICHMENT

    DEFF Research Database (Denmark)

    Nguyen, Thanh Viet; Vestergaard, Niels

    2009-01-01

    in the general ecosystem models. The objectives of this paper are modeling the impacts of nutrient enrichment on fisheries; particularly the impacts on consumer stocks and the fisheries based on these stocks are presented. We consider an aquatic ecosystem with four components: producers (autotrophs), consumers....... Consequently, consumer stocks are indirectly affected by pollution sources. Our model simulates these processes in the ecosystem.......  Economic models of fishery largely ignore the linkages to lower trophic levels. In particular, environmental data and other bottom-up information is widely disregarded. Nor are changes in physical environment (bottom-up) alongside both exogenous and endogenous environmental effects included...

  3. Quantifying nutrient export and deposition with a dynamic landscape evolution model for the lake Bolsena watershed, Italy

    Science.gov (United States)

    Pelorosso, Raffaele; Temme, Arnoud; Gobattoni, Federica; Leone, Antonio

    2010-05-01

    Excessive nutrient loads from upstream watershed activities such as agriculture, hydrological modifications, and urban runoff, have been identified as the leading cause of deterioration in assessed lakes and reservoirs (USEPA, 2000; Leone et al., 2001; Leone et al., 2003). Excessive nutrient transport into lakes and reservoirs may accelerate eutrophication rates, causing negative impacts on aesthetic and water quality. As reservoirs become eutrophic, they are depleted in oxygen and enriched in suspended solids, with heavy consequences for ecosystems and natural habitats. Management of nutrient loads into reservoirs requires knowledge of nutrient transport and delivery from the watershed-stream system (Ripa, 2003). Managing uncultivated lands in watersheds may be a cost effective way to improve water quality in agricultural landscapes, and recent advances in landscape ecology highlight important relationships between the structural configuration of these lands and nutrient redistribution (e.g., Forman 1987; Barrett and others 1990). Many studies have been carried out to underline and explain how landscape characteristics and structure may affect these processes. In these studies, relations between land cover and nutrient storage were analyzed using geographic information systems (GIS) (e.g. Lucas, 2002). Nutrients are generally transported from the landscape into streams during runoff events; however, they may also enter stream flow from other sources such as groundwater recharge and point source effluent discharges (Lucas, 2002; Nielsen, 2007; Waldron, 2008; Castillo, 2009). Water moves nutrients and delivers them to downstream water bodies such as lakes and reservoirs so that erosion phenomena play an essential role in determining nutrients fluxes and deposition. On the one hand, several hydrological models take into account nutrients reactions, movements and deposition - coupling soil erosion processes with transport equations (Bartley, 2004; Lű, 2010). On the

  4. Electricity load modelling using computational intelligence

    NARCIS (Netherlands)

    Ter Borg, R.W.

    2005-01-01

    As a consequence of the liberalisation of the electricity markets in Europe, market players have to continuously adapt their future supply to match their customers' demands. This poses the challenge of obtaining a predictive model that accurately describes electricity loads, current in this thesis.

  5. Nutrient loading and eutrophication of coastal waters of the South Asian Seas: a scoping study

    OpenAIRE

    2015-01-01

    This study looked at nutrient pollution and how it is affecting coastal and marine ecosystems in Bangladesh, India, Maldives, Pakistan and Sri Lanka. Causes it addressed included: agricultural practices; aquaculture; domestic sewage; industrial actions; and the burning of fossil fuels.

  6. Groundwater impacts on surface water quality and nutrient loads in lowland polder catchments: monitoring the greater Amsterdam area

    Science.gov (United States)

    Yu, Liang; Rozemeijer, Joachim; van Breukelen, Boris M.; Ouboter, Maarten; van der Vlugt, Corné; Broers, Hans Peter

    2018-01-01

    organic matter in subsurface sediments coupled to sulfate reduction and possibly methanogenesis. The large loads of nutrient-rich groundwater seepage into the deepest polders indirectly affect surface water quality in the surrounding area, because excess water from the deep polders is pumped out and used to supply water to the surrounding infiltrating polders in dry periods. The study shows the importance of the connection between groundwater and surface water nutrient chemistry in the greater Amsterdam area. We expect that taking account of groundwater-surface water interaction is also important in other subsiding and urbanising deltas around the world, where water is managed intensively in order to enable agricultural productivity and achieve water-sustainable cities.

  7. Groundwater impacts on surface water quality and nutrient loads in lowland polder catchments: monitoring the greater Amsterdam area

    Directory of Open Access Journals (Sweden)

    L. Yu

    2018-01-01

    from the decomposition of organic matter in subsurface sediments coupled to sulfate reduction and possibly methanogenesis. The large loads of nutrient-rich groundwater seepage into the deepest polders indirectly affect surface water quality in the surrounding area, because excess water from the deep polders is pumped out and used to supply water to the surrounding infiltrating polders in dry periods. The study shows the importance of the connection between groundwater and surface water nutrient chemistry in the greater Amsterdam area. We expect that taking account of groundwater–surface water interaction is also important in other subsiding and urbanising deltas around the world, where water is managed intensively in order to enable agricultural productivity and achieve water-sustainable cities.

  8. Sensitivity Study of Stochastic Walking Load Models

    DEFF Research Database (Denmark)

    Pedersen, Lars; Frier, Christian

    2010-01-01

    is to employ a stochastic load model accounting for mean values and standard deviations for the walking load parameters, and to use this as a basis for estimation of structural response. This, however, requires decisions to be made in terms of statistical istributions and their parameters, and the paper...... investigates whether statistical distributions of bridge response are sensitive to some of the decisions made by the engineer doing the analyses. For the paper a selected part of potential influences are examined and footbridge responses are extracted using Monte-Carlo simulations and focus is on estimating...

  9. Modelling Macroalgae Productivity In An Estuary. A Biorremediation To Nutrient Discharges In The Ecosystems.

    Science.gov (United States)

    Alvera-Azcárate, A.; Ferreira, J. G.; Nunes, J. P.

    Enhanced nutrient load to estuaries and coastal waters due to anthropogenic activities is damaging aquatic ecosystems, resulting in water pollution and eutrophication prob- lems. It is important to quantify the production of photosynthetic organisms, as they play an important role in controlling nitrogen removal and nitrogen fluxes between the sediments and the water column. In turbid estuaries, such as those on the NE Atlantic coast of Europe, benthic primary producers such as macroalgae may play an important part in carbon fixation and nutrient removal, since pelagic production is often strongly light-limited. Estuarine seaweeds are primarily located in intertidal areas, which are characterised by shallow waters and strong tidal currents. Due to high concentrations of suspended particulate matter in the water column, light is rapidly attenuated, limiting macroal- gae production during part of the tidal cycle. An accurate representation of sediment dynamics is essential for the determination of the light energy available for the algae, which is a key factor in reliable primary production estimates. In tidal flats, the sedi- ment dynamics is made more complex by the formation of tidal pools during low tide, where water quickly becomes clear, allowing more light to penetrate through the water column. In the present work a model is developed to calculate macroalgae production in the intertidal areas of estuaries, considering the factors mentioned above. The model is tested for the Tagus estuary (Portugal), and a Gross Primary Production of 3300 g m-2 y-1 was obtained. That results in a total nitrogen removal of 440 gN m-2 y-1. The results show that the macroalgae community plays an impor- tant role in the nitrogen cycle in estuaries and nutrient export to the open sea, acting as a biorremediation for the increased nutrient loading problem.

  10. Water and nutrient balances in a large tile-drained agricultural catchment: a distributed modeling study

    Directory of Open Access Journals (Sweden)

    H. Li

    2010-11-01

    Full Text Available This paper presents the development and implementation of a distributed model of coupled water nutrient processes, based on the representative elementary watershed (REW approach, to the Upper Sangamon River Basin, a large, tile-drained agricultural basin located in central Illinois, mid-west of USA. Comparison of model predictions with the observed hydrological and biogeochemical data, as well as regional estimates from literature studies, shows that the model is capable of capturing the dynamics of water, sediment and nutrient cycles reasonably well. The model is then used as a tool to gain insights into the physical and chemical processes underlying the inter- and intra-annual variability of water and nutrient balances. Model predictions show that about 80% of annual runoff is contributed by tile drainage, while the remainder comes from surface runoff (mainly saturation excess flow and subsurface runoff. It is also found that, at the annual scale nitrogen storage in the soil is depleted during wet years, and is supplemented during dry years. This carryover of nitrogen storage from dry year to wet year is mainly caused by the lateral loading of nitrate. Phosphorus storage, on the other hand, is not affected much by wet/dry conditions simply because the leaching of it is very minor compared to the other mechanisms taking phosphorous out of the basin, such as crop harvest. The analysis then turned to the movement of nitrate with runoff. Model results suggested that nitrate loading from hillslope into the channel is preferentially carried by tile drainage. Once in the stream it is then subject to in-stream denitrification, the significant spatio-temporal variability of which can be related to the variation of the hydrologic and hydraulic conditions across the river network.

  11. Improved hydrological-model design by integrating nutrient and water flow

    Science.gov (United States)

    Arheimer, B.; Lindstrom, G.

    2013-12-01

    separation of the hydrograph in surface flow, snow melt and baseflow, as well as horizontal flow paths in the landscape, such as mixing from various land use, impact from lakes and river channel volume. Overall, the S-HYPE model performance of water discharge increased from NSE 0.55 to 0.69 as an average for 400 gauges between the version 2010 and 2012. Most of this improvement, however, can be referred to improved regulations routines, rating curves for major lakes and parameters correcting ET and precipitation. Nevertheless, integrated water and nutrient modeling put constraints on the hydrological parameter values, which reduce equifinality for the hydrological part without reducing the model performance. The examples illustrates that the credibility of the hydrological model structure is thus improved by integrating water and nutrient flow. This lead to improved understanding of flow paths and water-nutrient process interactions in Sweden, which in turn will be very useful in further model analysis on impact of climate change or measures to reduce nutrient load from rivers to the Baltic Sea.

  12. Modelling of the Nutrient Medium for Plants Cultivation in Spaceflight

    Science.gov (United States)

    Nechitailo, Galina S.

    2016-07-01

    MODELLING OF THE NUTRIENT MEDIUM FOR PLANTS CULTIVATION IN SPACEFLIGHT Nechitajlo G.S.*, Rakhmetova A.A.**, Bogoslovskaja O.A.**, Ol'hovskay I.P.**, Glushchenko N.N.** *Emanuel Institute of Biochemical Physics of Russian Academy of Sciences (IBCP RAS) mail: spacemal@mail.ru **V.L. Talrose Institute for Energy Problems of Chemical Physics of Russian Academy of Science (INEPCP RAS) mail: nnglu@ mail.ru The valuable life and fruitful activity of cosmonauts and researchers in conditions of spaceflights and prolonged work at space stations are only possible with creating life area providing fresh air, natural food, comfortable psychological conditions, etc. The solution of that problem under space conditions seems impossible without use of high nano- and biotechnologies for plants growth. A priority should be given not only to choose species of growth plants in space, but also to improve conditions for their growth which includes optimal nourishing components for plants, preparation of nutrient mediums, illumination and temperature. We are deeply convinced that just manipulations with growing conditions for cultivated plants, but not genes changes, is a guarantee of success in the decision of this problem. For improving the method of plants growing on the artificial nutrient medium with balanced content of components, being necessary for growth and development of plants, we added essential metal elements: Fe, Zn, Cu - in an electroneutral state in the form of nanoparticles instead of sulfates or other easily dissolving salts. Nanoparticulated metals are known to have a number of advantages in comparison with salts: metals in an electroneutral form are characterized with the prolonged and multifunctional action, low toxicity per se and appearing to be much below the toxicity of the same metals in the ionic forms, accumulation as a reserve being used in biotic dozes, active distribution in bodies and organs of plants and stimulation of vital processes. A high reactivity

  13. Bayesian Modeling of the Assimilative Capacity Component of Stream Nutrient Export

    Science.gov (United States)

    Implementing stream restoration techniques and best management practices to reduce nonpoint source nutrients implies enhancement of the assimilative capacity for the stream system. In this paper, a Bayesian method for evaluating this component of a TMDL load capacity is developed...

  14. Steady state load models for power system analysis

    OpenAIRE

    Cresswell, Charles

    2009-01-01

    The last full review of load models used for power system studies occurred in the 1980s. Since then, new types of loads have been introduced and system load mix has changed considerably. The examples of newly introduced loads include drive-controlled motors, low energy consumption light sources and other modern power electronic loads. Their numbers have been steadily increasing in recent years, a trend which is expected to escalate. Accordingly, the majority of load models used...

  15. Modeling of STATCOM under different loading conditions

    DEFF Research Database (Denmark)

    George, G.J.; Ramachandran, Rakesh; Kowsalya, M.

    2012-01-01

    This paper deals with the study and analysis of Flexible AC Transmission Systems (FACTS), mainly the modeling of STATCOM. Reactive Power Compensation plays a very important role in the transmission of Electric Power. A comparative study of how the reactive power is injected into the transmission ...... system with and without STATCOM under different loading condition is also illustrated in this paper. Simulations are performed using MATLAB/SIMULINK software....

  16. Modelling of usual nutrient intakes: potential impact of the choices programme on nutrient intakes in young dutch adults.

    Directory of Open Access Journals (Sweden)

    Annet J C Roodenburg

    Full Text Available The Choices Programme is an internationally applicable nutrient profiling system with nutrition criteria for trans fatty acids (TFA, saturated fatty acids, sodium, added sugar and for some product groups energy and fibre. These criteria determine whether foods are eligible to carry a "healthier option" stamp. In this paper a nutrient intake modelling method is described to evaluate these nutritional criteria by investigating the potential effect on nutrient intakes.Data were combined from the 2003 Dutch food consumption survey in young adults (aged 19-30 and the Dutch food composition table into the Monte Carlo Risk Assessment model. Three scenarios were calculated: the "actual intakes" (scenario 1 were compared to scenario 2, where all foods that did not comply were replaced by similar foods that did comply with the Choices criteria. Scenario 3 was the same as scenario 2 adjusted for the difference in energy density between the original and replacement food. Additional scenarios were calculated where snacks were not or partially replaced and stratified analyses for gender, age, Body Mass Index (BMI and education.Calculated intake distributions showed that median energy intake was reduced by 16% by replacing normally consumed foods with Choices compliant foods. Intakes of nutrients with a maximal intake limit were also reduced (ranging from -23% for sodium and -62% for TFA. Effects on intakes of beneficial nutrients varied from an unintentional reduction in fat soluble vitamin intakes (-15 to -28% to an increase of 28% for fibre and 17% calcium. Stratified analyses in this homogeneous study population showed only small differences across gender, age, BMI and education.This intake modelling method showed that with consumption of Choices compliant foods, nutrient intakes shift towards population intake goals for the nutrients for which nutrition criteria were defined, while effects on beneficial nutrients were diverse.

  17. Modelling of Usual Nutrient Intakes: Potential Impact of the Choices Programme on Nutrient Intakes in Young Dutch Adults

    Science.gov (United States)

    Roodenburg, Annet J. C.; van Ballegooijen, Adriana J.; Dötsch-Klerk, Mariska; van der Voet, Hilko; Seidell, Jacob C.

    2013-01-01

    Introduction The Choices Programme is an internationally applicable nutrient profiling system with nutrition criteria for trans fatty acids (TFA), saturated fatty acids, sodium, added sugar and for some product groups energy and fibre. These criteria determine whether foods are eligible to carry a “healthier option” stamp. In this paper a nutrient intake modelling method is described to evaluate these nutritional criteria by investigating the potential effect on nutrient intakes. Methods Data were combined from the 2003 Dutch food consumption survey in young adults (aged 19–30) and the Dutch food composition table into the Monte Carlo Risk Assessment model. Three scenarios were calculated: the “actual intakes” (scenario 1) were compared to scenario 2, where all foods that did not comply were replaced by similar foods that did comply with the Choices criteria. Scenario 3 was the same as scenario 2 adjusted for the difference in energy density between the original and replacement food. Additional scenarios were calculated where snacks were not or partially replaced and stratified analyses for gender, age, Body Mass Index (BMI) and education. Results Calculated intake distributions showed that median energy intake was reduced by 16% by replacing normally consumed foods with Choices compliant foods. Intakes of nutrients with a maximal intake limit were also reduced (ranging from −23% for sodium and −62% for TFA). Effects on intakes of beneficial nutrients varied from an unintentional reduction in fat soluble vitamin intakes (−15 to −28%) to an increase of 28% for fibre and 17% calcium. Stratified analyses in this homogeneous study population showed only small differences across gender, age, BMI and education. Conclusions This intake modelling method showed that with consumption of Choices compliant foods, nutrient intakes shift towards population intake goals for the nutrients for which nutrition criteria were defined, while effects on beneficial

  18. Evaluation and use of U.S. Environmental Protection Agency Clean Watersheds Needs Survey data to quantify nutrient loads to surface water, 1978–2012

    Science.gov (United States)

    Ivahnenko, Tamara

    2017-12-07

    Changes in municipal and industrial point-source discharges over time have been an important factor affecting nutrient trends in many of the Nation’s streams and rivers. This report documents how three U.S. Environmental Protection Agency (EPA) national datasets—the Permit Compliance System, the Integrated Compliance Information System, and the Clean Watersheds Needs Survey—were evaluated for use in the U.S. Geological Survey National Water-Quality Assessment project to assess the causes of nutrient trends. This report also describes how a database of total nitrogen load and total phosphorous load was generated for select wastewater treatment facilities in the United States based on information reported in the EPA Clean Watersheds Needs Survey. Nutrient loads were calculated for the years 1978, 1980, 1982, 1984, 1986, 1988, 1990, 1992, 1996, 2000, 2004, 2008, and 2012 based on average nitrogen and phosphorous concentrations for reported treatment levels and on annual reported flow values.The EPA Permit Compliance System (PCS) and Integrated Compliance Information System (ICIS), which monitor point-source facility discharges, together are the Nation’s most spatially comprehensive dataset for nutrients released to surface waters. However, datasets for many individual facilities are incomplete, the PCS/ICIS historical data date back only to 1989, and historical data are available for only a limited number of facilities. Additionally, inconsistencies in facility reporting make it difficult to track or identify changes in nutrient discharges over time. Previous efforts made by the U.S. Geological Survey to “fill in” gaps in the PCS/ICIS data were based on statistical methods—missing data were filled in through the use of a statistical model based on the Standard Industrial Classification code, size, and flow class of the facility and on seasonal nutrient discharges of similar facilities. This approach was used to estimate point-source loads for a single

  19. Stochastic Load Models and Footbridge Response

    DEFF Research Database (Denmark)

    Pedersen, Lars; Frier, Christian

    2015-01-01

    Pedestrians may cause vibrations in footbridges and these vibrations may potentially be annoying. This calls for predictions of footbridge vibration levels and the paper considers a stochastic approach to modeling the action of pedestrians assuming walking parameters such as step frequency......, pedestrian mass, dynamic load factor, etc. to be random variables. By this approach a probability distribution function of bridge response is calculated. The paper explores how sensitive estimates of probability distribution functions of bridge response are to some of the decisions to be made when modelling...

  20. Predicting Footbridge Response using Stochastic Load Models

    DEFF Research Database (Denmark)

    Pedersen, Lars; Frier, Christian

    2013-01-01

    Walking parameters such as step frequency, pedestrian mass, dynamic load factor, etc. are basically stochastic, although it is quite common to adapt deterministic models for these parameters. The present paper considers a stochastic approach to modeling the action of pedestrians, but when doing so...... decisions need to be made in terms of statistical distributions of walking parameters and in terms of the parameters describing the statistical distributions. The paper explores how sensitive computations of bridge response are to some of the decisions to be made in this respect. This is useful...

  1. Intestinal Water Absorption Varies with Expected Dietary Water Load among Bats but Does Not Drive Paracellular Nutrient Absorption.

    Science.gov (United States)

    Price, Edwin R; Brun, Antonio; Gontero-Fourcade, Manuel; Fernández-Marinone, Guido; Cruz-Neto, Ariovaldo P; Karasov, William H; Caviedes-Vidal, Enrique

    2015-01-01

    Rapid absorption and elimination of dietary water should be particularly important to flying species and were predicted to vary with the water content of the natural diet. Additionally, high water absorption capacity was predicted to be associated with high paracellular nutrient absorption due to solvent drag. We compared the water absorption rates of sanguivorous, nectarivorous, frugivorous, and insectivorous bats in intestinal luminal perfusions. High water absorption rates were associated with high expected dietary water load but were not highly correlated with previously measured rates of (paracellular) arabinose clearance. In conjunction with these tests, we measured water absorption and the paracellular absorption of nutrients in the intestine and stomach of vampire bats using luminal perfusions to test the hypothesis that the unique elongated vampire stomach is a critical site of water absorption. Vampire bats' gastric water absorption was high compared to mice but not compared to their intestines. We therefore conclude that (1) dietary water content has influenced the evolution of intestinal water absorption capacity in bats, (2) solvent drag is not the only driver of paracellular nutrient absorption, and (3) the vampire stomach is a capable but not critical location for water absorption.

  2. Longitudinal Loading and Nutrient Compositional Gradients in an Agriculturally Managed Watershed in West-Central Wisconsin

    National Research Council Canada - National Science Library

    James, William F; Ruiz, Carlos E; Barko, John W; Eakin, Harry L

    2004-01-01

    The purpose of this research was to describe and quantify biologically labile and refractory nitrogen and phosphorus species, transformations, and loads along the longitudinal axis of a river draining...

  3. Hierarchy of factors exerting an impact on nutrient load of the Baltic Sea and sustainable management of its drainage basin.

    Science.gov (United States)

    Kiedrzyńska, Edyta; Jóźwik, Adam; Kiedrzyński, Marcin; Zalewski, Maciej

    2014-11-15

    The aim of the paper was to evaluate 23 catchment factors that determine total phosphorus and total nitrogen load to the Baltic Sea. Standard correlation analysis and clustering were used. Both phosphorus and nitrogen loads were found to be positively related to the number of pigs and the human population associated with wastewater treatment plants (WWTPs) per km(2), while the number of cattle and agricultural area were found to influence nitrogen rather than phosphorus load, and the area of forests is negatively related to loads of both nutrients. Clustering indicates an overall north-south pattern in the spatial co-occurrence of socio-ecological factors, with some exceptions discussed in the paper. Positive steps in the Baltic Sea region have already been taken, but much remains to be done. The development of coherent response policies to reduce eutrophication in the Baltic Sea should be based on a comprehensive knowledge base, an appropriate information strategy and learning alliance platform in each drainage river catchments. Copyright © 2014 Elsevier Ltd. All rights reserved.

  4. Chemical fractionation of lake sediments to determine the effects of land-use change on nutrient loading

    Science.gov (United States)

    Heathwaite, A. L.

    1994-07-01

    Lake studies allow contemporary sediment and nutrient dynamics to be placed in a historical context in order that trends and rates of change in catchment inputs may be calculated. Here, a synthesis of the temporal information contained in catchment and lake sediment records is attempted. A chemical fractionation technique is used to isolate the different sediment sources contained in the lake core, and 210Pb dates provide an accurate record of changes in lake sediment sources over the past 100 years. The extent to which land-use records, collated from agricultural census returns, and process-based studies of sediment and nutrient export from different catchment land uses can be used to explain the trends observed in the lake sediments is examined. Sediment influx to the study lake has increased from less than 2 mm year -1 prior to the Second World War to over 10 mm year -1 at present. The source of the sediment is largely unaltered and unweathered allochthonous material eroded from the catchment. Land-use records suggest that the intensification of agriculture, characterized by a shift towards arable land immediately postwar, followed by an increase in the area of temporary grass in the 1960s, may be the cause of accelerated catchment erosion; both land-use changes would have increased the area of ploughed land in the catchment. An increase in the number of cattle and sheep in the catchment from around 2000 and 6000, respectively, in the 1940s, to a peak of nearly 7000 cattle and over 15 000 sheep in the 1980s, provides a further source of sediment and nutrients. Livestock are grazed on permanent grassland which is commonly located on steep hillslopes and in riparian zones where saturation-excess surface runoff may be an important hydrological pathway. Rainfall simulation experiments show that surface runoff from heavily grazed grassland has a high suspended sediment, ammonium-nitrogen and particulate phosphorus load. The combined effect of the long-term increase

  5. Estimates of Nutrient Loading by Ground-Water Discharge into the Lynch Cove Area of Hood Canal, Washington

    Science.gov (United States)

    Simonds, F. William; Swarzenski, Peter W.; Rosenberry, Donald O.; Reich, Christopher D.; Paulson, Anthony J.

    2008-01-01

    Low dissolved oxygen concentrations in the waters of Hood Canal threaten marine life in late summer and early autumn. Oxygen depletion in the deep layers and landward reaches of the canal is caused by decomposition of excess phytoplankton biomass, which feeds on nutrients (primarily nitrogen compounds) that enter the canal from various sources, along with stratification of the water column that prevents mixing and replenishment of oxygen. Although seawater entering the canal is the largest source of nitrogen, ground-water discharge to the canal also contributes significant quantities, particularly during summer months when phytoplankton growth is most sensitive to nutrient availability. Quantifying ground-water derived nutrient loads entering an ecologically sensitive system such as Hood Canal is a critical component of constraining the total nutrient budget and ultimately implementing effective management strategies to reduce impacts of eutrophication. The amount of nutrients entering Hood Canal from ground water was estimated using traditional and indirect measurements of ground-water discharge, and analysis of nutrient concentrations. Ground-water discharge to Hood Canal is variable in space and time because of local geology, variable hydraulic gradients in the ground-water system adjacent to the shoreline, and a large tidal range of 3 to 5 meters. Intensive studies of ground-water seepage and hydraulic-head gradients in the shallow, nearshore areas were used to quantify the freshwater component of submarine ground-water discharge (SGD), whereas indirect methods using radon and radium geochemical tracers helped quantify total SGD and recirculated seawater. In areas with confirmed ground-water discharge, shore-perpendicular electrical resistivity profiles, continuous electromagnetic seepage-meter measurements, and continuous radon measurements were used to visualize temporal variations in ground-water discharge over several tidal cycles. The results of these

  6. Modeling, Estimation, and Control of Helicopter Slung Load System

    DEFF Research Database (Denmark)

    Bisgaard, Morten

    . This first major contribution of this thesis is the development of a complete helicopter and slung load system model that is shared between the two branches. The generic slung load model can be used to model all body to body slung load suspension types and gives an intuitive and easy-to-use way of modeling...

  7. SPARROW models used to understand nutrient sources in the Mississippi/Atchafalaya River Basin

    Science.gov (United States)

    Robertson, Dale M.; Saad, David A.

    2013-01-01

    Nitrogen (N) and phosphorus (P) loading from the Mississippi/Atchafalaya River Basin (MARB) has been linked to hypoxia in the Gulf of Mexico. To describe where and from what sources those loads originate, SPAtially Referenced Regression On Watershed attributes (SPARROW) models were constructed for the MARB using geospatial datasets for 2002, including inputs from wastewater treatment plants (WWTPs), and calibration sites throughout the MARB. Previous studies found that highest N and P yields were from the north-central part of the MARB (Corn Belt). Based on the MARB SPARROW models, highest N yields were still from the Corn Belt but centered over Iowa and Indiana, and highest P yields were widely distributed throughout the center of the MARB. Similar to that found in other studies, agricultural inputs were found to be the largest N and P sources throughout most of the MARB: farm fertilizers were the largest N source, whereas farm fertilizers, manure, and urban inputs were dominant P sources. The MARB models enable individual N and P sources to be defined at scales ranging from SPARROW catchments (∼50 km2) to the entire area of the MARB. Inputs of P from WWTPs and urban areas were more important than found in most other studies. Information from this study will help to reduce nutrient loading from the MARB by providing managers with a description of where each of the sources of N and P are most important, thus providing a basis for prioritizing management actions and ultimately reducing the extent of Gulf hypoxia.

  8. Mycorrhizal fungi reduce nutrient loss from model grassland ecosystems.

    NARCIS (Netherlands)

    van der Heijden, M.G.A.

    2010-01-01

    Nutrient loss from ecosystems is among the top environmental threats to ecosystems worldwide, leading to reduced plant productivity in nutrient-poor ecosystems and eutrophication of surface water near nutrient-rich ecosystems. Hence, it is of pivotal importance to understand which factors influence

  9. Optimizing simulated fertilizer additions using a genetic algorithm with a nutrient uptake model

    Science.gov (United States)

    Wendell P. Cropper; N.B. Comerford

    2005-01-01

    Intensive management of pine plantations in the southeastern coastal plain typically involves weed and pest control, and the addition of fertilizer to meet the high nutrient demand of rapidly growing pines. In this study we coupled a mechanistic nutrient uptake model (SSAND, soil supply and nutrient demand) with a genetic algorithm (GA) in order to estimate the minimum...

  10. Research Paper. Nutrient uptake and mineralization during leaf decay in streams-a model simulation.

    Science.gov (United States)

    J.R. Webster; J.D. Newbold; S.A. Thomas; H.M. Valett; P.J. Mulholland

    2009-01-01

    We developed a stoichiometrically explicit computer model to examine how heterotrophic uptake of nutrients and microbial mineralization occurring during the decay of leaves in streams may be important in modifying nutrient concentrations. The simulations showed that microbial uptake can substantially decrease stream nutrient concentrations during the initial phases of...

  11. Multiple models guide strategies for agricultural nutrient reductions

    Science.gov (United States)

    Scavia, Donald; Kalcic, Margaret; Muenich, Rebecca Logsdon; Read, Jennifer; Aloysius, Noel; Bertani, Isabella; Boles, Chelsie; Confesor, Remegio; DePinto, Joseph; Gildow, Marie; Martin, Jay; Redder, Todd; Robertson, Dale M.; Sowa, Scott P.; Wang, Yu-Chen; Yen, Haw

    2017-01-01

    In response to degraded water quality, federal policy makers in the US and Canada called for a 40% reduction in phosphorus (P) loads to Lake Erie, and state and provincial policy makers in the Great Lakes region set a load-reduction target for the year 2025. Here, we configured five separate SWAT (US Department of Agriculture's Soil and Water Assessment Tool) models to assess load reduction strategies for the agriculturally dominated Maumee River watershed, the largest P source contributing to toxic algal blooms in Lake Erie. Although several potential pathways may achieve the target loads, our results show that any successful pathway will require large-scale implementation of multiple practices. For example, one successful pathway involved targeting 50% of row cropland that has the highest P loss in the watershed with a combination of three practices: subsurface application of P fertilizers, planting cereal rye as a winter cover crop, and installing buffer strips. Achieving these levels of implementation will require local, state/provincial, and federal agencies to collaborate with the private sector to set shared implementation goals and to demand innovation and honest assessments of water quality-related programs, policies, and partnerships.

  12. Global Expanded Nutrient Supply (GENuS Model: A New Method for Estimating the Global Dietary Supply of Nutrients.

    Directory of Open Access Journals (Sweden)

    Matthew R Smith

    Full Text Available Insufficient data exist for accurate estimation of global nutrient supplies. Commonly used global datasets contain key weaknesses: 1 data with global coverage, such as the FAO food balance sheets, lack specific information about many individual foods and no information on micronutrient supplies nor heterogeneity among subnational populations, while 2 household surveys provide a closer approximation of consumption, but are often not nationally representative, do not commonly capture many foods consumed outside of the home, and only provide adequate information for a few select populations. Here, we attempt to improve upon these datasets by constructing a new model--the Global Expanded Nutrient Supply (GENuS model--to estimate nutrient availabilities for 23 individual nutrients across 225 food categories for thirty-four age-sex groups in nearly all countries. Furthermore, the model provides historical trends in dietary nutritional supplies at the national level using data from 1961-2011. We determine supplies of edible food by expanding the food balance sheet data using FAO production and trade data to increase food supply estimates from 98 to 221 food groups, and then estimate the proportion of major cereals being processed to flours to increase to 225. Next, we estimate intake among twenty-six demographic groups (ages 20+, both sexes in each country by using data taken from the Global Dietary Database, which uses nationally representative surveys to relate national averages of food consumption to individual age and sex-groups; for children and adolescents where GDD data does not yet exist, average calorie-adjusted amounts are assumed. Finally, we match food supplies with nutrient densities from regional food composition tables to estimate nutrient supplies, running Monte Carlo simulations to find the range of potential nutrient supplies provided by the diet. To validate our new method, we compare the GENuS estimates of nutrient supplies against

  13. Water quality, nutrient budget, and pollutant loads in Chinese mitten crab ( Eriocheir sinensis) farms around East Taihu Lake

    Science.gov (United States)

    Cai, Chunfang; Gu, Xiaohong; Huang, Hezhong; Dai, Xiuying; Ye, Yuantu; Shi, Chenjiang

    2012-01-01

    To understand the factors causing frequent outbreaks of harmful algae blooms in the Taihu Lake, China, we studied water quality and nutrient budget in Chinese mitten crab ( Eriocheir sinensis) farm ponds in the eastern part of the lake from November 2007 to December 2009. We estimated the nitrogen (N), phosphorus (P), and chemical oxygen demand (COD) loads. Materials input and output ponds, water exchange, and applied management practices of 838.5-hm2 crab ponds were surveyed using questionnaires. Water quality of 12 ponds, which were located no more than 2 km from East Taihu Lake, were monitored. The results show that water quality in the crab ponds was better than reference data. Feeds, including corn seed, commercial feed, trash fish, and gastropod, were the major sources of N and P input in the crab ponds, contributing 88.7% and 94.9%, respectively. In total, 60.5% of N and 37.3% of P were sequestered by macrophytes, and only 15.7% and 8.5% of them were discharged as effluent. The net loads of N and P in effluent were 16.43 kg/hm2/cycle and 2.16 kg/hm2/cycle, respectively, while the COD load was -17.88 kg/hm2/cycle. This indicated that crab farming caused minor negative impact on the trophic status of the lake area, which was attenuated by macrophytes. However, wastewater purification is still necessary in crab faming.

  14. Short-Term Effects of Drying-Rewetting and Long-Term Effects of Nutrient Loading on Periphyton N:P Stoichiometry

    Directory of Open Access Journals (Sweden)

    Andres D. Sola

    2018-01-01

    Full Text Available Nitrogen (N and phosphorus (P concentrations and N:P ratios critically influence periphyton productivity and nutrient cycling in aquatic ecosystems. In coastal wetlands, variations in hydrology and water source (fresh or marine influence nutrient availability, but short-term effects of drying and rewetting and long-term effects of nutrient exposure on periphyton nutrient retention are uncertain. An outdoor microcosm experiment simulated short-term exposure to variation in drying-rewetting frequency on periphyton mat nutrient retention. A 13-year dataset from freshwater marshes of the Florida Everglades was examined for the effect of long-term proximity to different N and P sources on mat-forming periphyton nutrient standing stocks and stoichiometry. Field sites were selected from one drainage with shorter hydroperiod and higher connectivity to freshwater anthropogenic nutrient supplies (Taylor Slough/Panhandle, TS/Ph and another drainage with longer hydroperiod and higher connectivity to marine nutrient supplies (Shark River Slough, SRS. Total P, but not total N, increased in periphyton mats exposed to both low and high drying-rewetting frequency with respect to the control mats in our experimental microcosm. In SRS, N:P ratios slightly decreased downstream due to marine nutrient supplies, while TS/Ph increased. Mats exposed to short-term drying-rewetting had higher nutrient retention, similar to nutrient standing stocks from long-term field data. Periphyton mat microbial communities may undergo community shifts upon drying-rewetting and chronic exposure to nutrient loads. Additional work on microbial species composition may further explain how periphyton communities interact with drying-rewetting dynamics to influence nutrient cycling and retention in wetlands.

  15. Evaluation of nutrient load transferred from Sarca river into Garda lake; Stima del carico di nutrienti trasportato dal fiume Sarca nel Lago di Garda

    Energy Technology Data Exchange (ETDEWEB)

    Marchetti, F. [Istituto Agrario, S. Michele all' Adige, TN (Italy); Fravezzi, L. [Agenzia Provinciale Protezione Ambiente, Trient (Italy)

    2000-02-01

    River Sarca (catchment surface=1046 Km{sup 2} max altitude=3556 m, min altitude=70 m, mean annual discharge=30 m{sup 3}) is the main tributary of the Lake Garda, the largest subalpine lake in Northern Italy (area=370 Km{sup 2,} catchment surface (included lake surface)=2260 Km{sup 2}, volume=49 Km{sup 3}, max depth=346 m). During 1996-97 a large series of hourly samples has been taken at the estuary's mouth and used to estimate the nutrient loading. Analytical and probabilistic methods are used to relate the data series to the trophic state of the lake. The results are compared with previous theoretical models (L.E.M.- Loading Evaluation Model) and related to dangerous load levels established by OECD. [Italian] L'indagine ha interessato particolarmente le concentrazioni ed il carico organico ed inorganico di azoto e fosforo che affluisce dal bacino del Fiume Sarca (superficie del bacino=1046 km{sup 2,} quota massima=3556 m, quota minima=70 m, portata media annua=30 m{sup 3}) nel Lago di Garda (area=370 km{sup 2}, area del bacino (lago incluso)=2260 km{sup 2}, volume=49 km{sup 3}, profondita' massima=346 m); lo studio si e' svolto nel periodo 1996-1997, con campionamenti presso la foce utilizzando strumentazione per prelievi in continuo nell'arco di una giornata anche in occasione di fenomeni di piena. I risultati hanno permesso di stabilire delle relazioni tra carico e portata liquida e di stimare i quantitativi di nutrienti trasportati a lago e di confrontarli con i risultati di altre indagini (L.E.M. - Loading Evaluation Model) e di valutarne gli effetti attraverso modelli predittivi (OECD).

  16. Modelling of nutrient partitioning in growing pigs to predict their anatomical body composition. 1. Model description

    NARCIS (Netherlands)

    Halas, V.; Dijkstra, J.; Babinszky, L.; Verstegen, M.W.A.; Gerrits, W.J.J.

    2004-01-01

    A dynamic mechanistic model was developed for growing and fattening pigs. The aim of the model was to predict growth rate and the chemical and anatomical body compositions from the digestible nutrient intake of gilts (20-105 kg live weight). The model represents the partitioning of digestible

  17. Advancing waterborne pathogen modelling: lessons from global nutrient export models

    NARCIS (Netherlands)

    Vermeulen, L.C.; Hofstra, N.; Kroeze, C.; Medema, G.J.

    2015-01-01

    Waterborne pathogens cause health problems worldwide. A global waterborne pathogen model could provide valuable new insights for data-sparse regions, by identifying pathogen hotspots and evaluating global change and risk management scenarios. Global waterborne pathogen modelling is not as advanced

  18. Trends in nutrient concentrations, loads, and yields in streams in the Sacramento, San Joaquin, and Santa Ana Basins, California, 1975-2004

    Science.gov (United States)

    Kratzer, Charles R.; Kent, Robert; Seleh, Dina K.; Knifong, Donna L.; Dileanis, Peter D.; Orlando, James L.

    2011-01-01

    San Joaquin Basin but decreased in the Sacramento and Santa Ana Basins from 1982 to 2002. Tile drainage accounted for 22 percent of the total nitrogen load in the San Joaquin River near Vernalis for 1985-2004. Nutrient loads and trends were calculated by using the log-linear multiple-regression model, LOADEST. Loads were calculated for water years 1975-2004 for 22 sites in the Sacramento Basin, 15 sites in the San Joaquin Basin, and 6 sites in the Santa Ana Basin. The average annual load of total nitrogen and total phosphorus for 1985-2004 in subbasins in the Sacramento and San Joaquin Basins were divided by their drainage areas to calculate average annual yield. Total nitrogen yields were greater than 2.45 tons per square mile per year [(tons/mi2)/yr] in about 61 percent of the valley floor in the San Joaquin Basin compared with only about 12 percent of the valley floor in the Sacramento Basin. Total phosphorus yields were greater than 0.34 (tons/mi2)/yr in about 43 percent of the valley floor in the San Joaquin Basin compared with only about 5 percent in the valley floor of the Sacramento Basin. In a stepwise multiple linear-regression analysis of 30 subbasins in the Sacramento and San Joaquin Basins, the most important explanatory variables (out of 11 variables) for the response variable (total nitrogen yield) were the percentage of land use in (1) orchards and vineyards, (2) row crops, and (3) urban categories. For total phosphorus yield, the most important explanatory variable was the amount of fertilizer application plus manure production. Trends were evaluated for three time periods: 1975-2004, 1985-2004, and 1993-2004. Most trends in flow-adjusted concentrations of nutrients in the Sacramento Basin were downward for all three time periods. The decreasing nutrient trends in the American River at Sacramento and the Sacramento River at Freeport for 1975-2004 were attributed to the consolidation of wastewater in the Sacramento metropolitan area in December 1982 to

  19. Diet-dependent net endogenous acid load of vegan diets in relation to food groups and bone health-related nutrients: results from the German Vegan Study.

    Science.gov (United States)

    Ströhle, Alexander; Waldmann, Annika; Koschizke, Jochen; Leitzmann, Claus; Hahn, Andreas

    2011-01-01

    Dietary composition has been shown to affect acid-base homeostasis and bone health in humans. We investigated the potential renal acid load (PRAL) and the estimated diet-dependent net acid load (net endogenous acid production, NEAP) in adult vegans and evaluated the relationships between NEAP, food groups and intake of bone health-related nutrients. The German Vegan Study (GVS) is a cross-sectional study. Data from healthy men (n = 67) and women (n = 87), aged 21-75 years, who fulfilled the study criteria (vegan diet for ≥1 year prior to study start; age ≥18 years, and no pregnancy/childbirth during the last 12 months) were included in the analysis. NEAP values were calculated from diet composition using two models: one based on the protein/potassium quotient and another taking into account an anthropometry-based loss of urinary organic anions. Mean daily intakes of phosphorus, potassium, sodium, magnesium and vitamin C were above, and vitamin D and calcium below Dietary Reference Intake (DRI). Regardless of the model used, the diet in the GVS was characterized by a nearly neutral NEAP. A strong correlation was observed between the NEAP values of the two models (r(s) = 0.873, p vegan diets do not affect acid-base homeostasis. With respect to bone health, the significance of this finding needs further investigation. Copyright © 2011 S. Karger AG, Basel.

  20. The MARINA model (Model to Assess River Inputs of Nutrients to seAs): Model description and results for China.

    Science.gov (United States)

    Strokal, Maryna; Kroeze, Carolien; Wang, Mengru; Bai, Zhaohai; Ma, Lin

    2016-08-15

    Chinese agriculture has been developing fast towards industrial food production systems that discharge nutrient-rich wastewater into rivers. As a result, nutrient export by rivers has been increasing, resulting in coastal water pollution. We developed a Model to Assess River Inputs of Nutrients to seAs (MARINA) for China. The MARINA Nutrient Model quantifies river export of nutrients by source at the sub-basin scale as a function of human activities on land. MARINA is a downscaled version for China of the Global NEWS-2 (Nutrient Export from WaterSheds) model with an improved approach for nutrient losses from animal production and population. We use the model to quantify dissolved inorganic and organic nitrogen (N) and phosphorus (P) export by six large rivers draining into the Bohai Gulf (Yellow, Hai, Liao), Yellow Sea (Yangtze, Huai) and South China Sea (Pearl) in 1970, 2000 and 2050. We addressed uncertainties in the MARINA Nutrient model. Between 1970 and 2000 river export of dissolved N and P increased by a factor of 2-8 depending on sea and nutrient form. Thus, the risk for coastal eutrophication increased. Direct losses of manure to rivers contribute to 60-78% of nutrient inputs to the Bohai Gulf and 20-74% of nutrient inputs to the other seas in 2000. Sewage is an important source of dissolved inorganic P, and synthetic fertilizers of dissolved inorganic N. Over half of the nutrients exported by the Yangtze and Pearl rivers originated from human activities in downstream and middlestream sub-basins. The Yellow River exported up to 70% of dissolved inorganic N and P from downstream sub-basins and of dissolved organic N and P from middlestream sub-basins. Rivers draining into the Bohai Gulf are drier, and thus transport fewer nutrients. For the future we calculate further increases in river export of nutrients. The MARINA Nutrient model quantifies the main sources of coastal water pollution for sub-basins. This information can contribute to formulation of

  1. Global Expanded Nutrient Supply (GENuS) Model: A New Method for Estimating the Global Dietary Supply of Nutrients

    Science.gov (United States)

    Golden, Christopher D.; Mozaffarian, Dariush

    2016-01-01

    Insufficient data exist for accurate estimation of global nutrient supplies. Commonly used global datasets contain key weaknesses: 1) data with global coverage, such as the FAO food balance sheets, lack specific information about many individual foods and no information on micronutrient supplies nor heterogeneity among subnational populations, while 2) household surveys provide a closer approximation of consumption, but are often not nationally representative, do not commonly capture many foods consumed outside of the home, and only provide adequate information for a few select populations. Here, we attempt to improve upon these datasets by constructing a new model—the Global Expanded Nutrient Supply (GENuS) model—to estimate nutrient availabilities for 23 individual nutrients across 225 food categories for thirty-four age-sex groups in nearly all countries. Furthermore, the model provides historical trends in dietary nutritional supplies at the national level using data from 1961–2011. We determine supplies of edible food by expanding the food balance sheet data using FAO production and trade data to increase food supply estimates from 98 to 221 food groups, and then estimate the proportion of major cereals being processed to flours to increase to 225. Next, we estimate intake among twenty-six demographic groups (ages 20+, both sexes) in each country by using data taken from the Global Dietary Database, which uses nationally representative surveys to relate national averages of food consumption to individual age and sex-groups; for children and adolescents where GDD data does not yet exist, average calorie-adjusted amounts are assumed. Finally, we match food supplies with nutrient densities from regional food composition tables to estimate nutrient supplies, running Monte Carlo simulations to find the range of potential nutrient supplies provided by the diet. To validate our new method, we compare the GENuS estimates of nutrient supplies against independent

  2. Data to support "Boosted Regression Tree Models to Explain Watershed Nutrient Concentrations & Biological Condition"

    Data.gov (United States)

    U.S. Environmental Protection Agency — Spreadsheets are included here to support the manuscript "Boosted Regression Tree Models to Explain Watershed Nutrient Concentrations and Biological Condition". This...

  3. Development and use of a bioeconomic model for management of mussel fisheries under different nutrient regimes in the temperate estuary of the Limfjord, Denmark

    DEFF Research Database (Denmark)

    Timmermann, Karen; Dinesen, Grete E.; Markager, Stiig

    2014-01-01

    Coastal ecosystems worldwide are under pressure from human-induced nutrient inputs, fishing activities, mariculture, construction work, and climate change. Integrated management instruments handling one or more of these problems in combination with socioeconomic issues are therefore necessary...... to secure a sustainable use of resources. In the Limfjord, a temperate eutrophic estuary in Denmark, nutrient load reductions are necessary to fulfill EU regulations such as the Water Framework Directive (WFD). The expected outcome of these load reductions is an improved water quality, but also reduced...... reductions for mussel fishery as practiced today, as well as potential management options, to obtain an economically and ecologically sustainable mussel fishery. Model simulations clearly demonstrate a substantial decrease in mussel production after the nutrient load reductions necessary to obtain...

  4. Kinetic model of a granular sludge SBR: influences on nutrient removal.

    Science.gov (United States)

    de Kreuk, M K; Picioreanu, C; Hosseini, M; Xavier, J B; van Loosdrecht, M C M

    2007-07-01

    A mathematical model was developed that can be used to describe an aerobic granular sludge reactor, fed with a defined influent, capable of simultaneously removing COD, nitrogen and phosphate in one sequencing batch reactor (SBR). The model described the experimental data from this complex system sufficiently. The effect of process parameters on the nutrient removal rates could therefore be reliably evaluated. The influence of oxygen concentration, temperature, granule diameter, sludge loading rate, and cycle configuration were analyzed. Oxygen penetration depth in combination with the position of the autotrophic biomass played a crucial role in the conversion rates of the different components and thus on overall nutrient removal efficiencies. The ratio between aerobic and anoxic volume in the granule strongly determines the N-removal efficiency as it was shown by model simulations with varying oxygen concentration, temperature, and granule size. The optimum granule diameter for maximum N- and P-removal in the standard case operating conditions (DO 2 mg L(-1), 20 degrees C) was found between 1.2 and 1.4 mm and the optimum COD loading rate was 1.9 kg COD m(-3) day(-1). When all ammonia is oxidized, oxygen diffuses to the core of the granule inhibiting the denitrification process. In order to optimize the process, anoxic phases can be implemented in the SBR-cycle configuration, leading to a more efficient overall N-removal. Phosphate removal efficiency mainly depends on the sludge age; if the SRT exceeds 30 days not enough biomass is removed from the system to keep effluent phosphate concentrations low. (c) 2006 Wiley Periodicals, Inc.

  5. Modeling of porous concrete elements under load

    Science.gov (United States)

    Demchyna, B. H.; Famuliak, Yu. Ye.; Demchyna, Kh. B.

    2017-12-01

    It is known that cell concretes are almost immediately destroyed under load, having reached certain critical stresses. Such kind of destruction is called a "catastrophic failure". Process of crack formation is one of the main factors, influencing process of concrete destruction. Modern theory of crack formation is mainly based on the Griffith theory of destruction. However, the mentioned theory does not completely correspond to the structure of cell concrete with its cell structure, because the theory is intended for a solid body. The article presents one of the possible variants of modelling of the structure of cell concrete and gives some assumptions concerning the process of crack formation in such hollow, not solid environment.

  6. Modeling of porous concrete elements under load

    Directory of Open Access Journals (Sweden)

    Demchyna B.H.

    2017-12-01

    Full Text Available It is known that cell concretes are almost immediately destroyed under load, having reached certain critical stresses. Such kind of destruction is called a “catastrophic failure”. Process of crack formation is one of the main factors, influencing process of concrete destruction. Modern theory of crack formation is mainly based on the Griffith theory of destruction. However, the mentioned theory does not completely correspond to the structure of cell concrete with its cell structure, because the theory is intended for a solid body. The article presents one of the possible variants of modelling of the structure of cell concrete and gives some assumptions concerning the process of crack formation in such hollow, not solid environment.

  7. Dominance patterns in macroalgal and phytoplankton biomass under different nutrient loads in subtropical coastal lagoons of the SE Gulf of California

    International Nuclear Information System (INIS)

    Páez-Osuna, F.; Piñón-Gimate, A.; Ochoa-Izaguirre, M.J.

    2013-01-01

    Highlights: • Nine macroalgal blooms were examined in five lagoons from SE Gulf of California. • Shrimp farms were the main point source of nutrients loads to the lagoons. • Biomass as phytoplankton ranged 40–792 mg m −2 and macroalgal of 1–296 g m −2 . • Biomass (phytoplankton + macroalgae) was the same tendency that nutrient loads. • Phytoplankton and macroalgal biomass were a significant correlation with N:P ratio. -- Abstract: Nine macroalgal blooms were studied in five coastal lagoons of the SE Gulf of California. The nutrient loads from point and diffuse sources were estimated in the proximity of the macroalgal blooms. Chlorophyll a and macroalgal biomass were measured during the dry, rainy and cold seasons. Shrimp farms were the main point source of nitrogen and phosphorus loads for the lagoons. High biomasses were found during the dry season for phytoplankton at site 6 (791.7 ± 34.6 mg m −2 ) and during the rainy season for macroalgae at site 4 (296.0 ± 82.4 g m −2 ). Depending on the season, the phytoplankton biomass ranged between 40.0 and 791.7 mg m −2 and the macroalgal biomass between 1 and 296.0 g m −2 . The bulk biomass (phytoplankton + macroalgal) displayed the same tendency as the nutrient loads entering the coastal lagoons. Phytoplankton and macroalgal biomass presented a significant correlation with the atomic N:P ratio

  8. Nutrient uptake and mineralization during leaf decay in streams - a model simulation

    Energy Technology Data Exchange (ETDEWEB)

    Webster, Jackson [Virginia Polytechnic Institute and State University (Virginia Tech); Newbold, J. Denis [Stroud Water Research Center; Thomas, Steve [University of Nebraska; Valett, H. Maurice [Virginia Polytechnic Institute and State University (Virginia Tech); Mulholland, Patrick J [ORNL

    2009-01-01

    We developed a stoichiometrically explicit computer model to examine how heterotrophic uptake of nutrients and microbial mineralization occurring during the decay of leaves in streams may be important in modifying nutrient concentrations. The simulations showed that microbial uptake can substantially decrease stream nutrient concentrations during the initial phases of decomposition, while mineralization may produce increases in concentrations during later stages of decomposition. The simulations also showed that initial nutrient content of the leaves can affect the stream nutrient concentration dynamics and determine whether nitrogen or phosphorus is the limiting nutrient. Finally, the simulations suggest a net retention (uptake > mineralization) of nutrients in headwater streams, which is balanced by export of particulate organic nutrients to downstream reaches. Published studies support the conclusion that uptake can substantially change stream nutrient concentrations. On the other hand, there is little published evidence that mineralization also affects nutrient concentrations. Also, there is little information on direct microbial utilization of nutrients contained in the decaying leaves themselves. Our results suggest several directions for research that will improve our understanding of the complex relationship between leaf decay and nutrient dynamics in streams.

  9. Nutrient losses by wind and water, measurements and modelling

    NARCIS (Netherlands)

    Visser, S.M.; Stroosnijder, L.; Chardon, W.J.

    2005-01-01

    In the Sahelian zone of West-Africa, erosion by both wind and water causes a serious decline in fertility of the already low fertile soils. Despite the fact that the flow of nutrients has been intensively investigated by the use of nutrient balances, little attention has been paid to the

  10. Nutrient delivery to Lake Winnipeg from the Red-Assiniboine River Basin – A binational application of the SPARROW model

    Science.gov (United States)

    Benoy, Glenn A; Jenkinson, R. Wayne; Robertson, Dale M.; Saad, David A.

    2016-01-01

    Excessive phosphorus (TP) and nitrogen (TN) inputs from the Red–Assiniboine River Basin (RARB) have been linked to eutrophication of Lake Winnipeg; therefore, it is important for the management of water resources to understand where and from what sources these nutrients originate. The RARB straddles the Canada–United States border and includes portions of two provinces and three states. This study represents the first binationally focused application of SPAtially Referenced Regressions on Watershed attributes (SPARROW) models to estimate loads and sources of TP and TN by jurisdiction and basin at multiple spatial scales. Major hurdles overcome to develop these models included: (1) harmonization of geospatial data sets, particularly construction of a contiguous stream network; and (2) use of novel calibration steps to accommodate limitations in spatial variability across the model extent and in the number of calibration sites. Using nutrient inputs for a 2002 base year, a RARB TP SPARROW model was calibrated that included inputs from agriculture, forests and wetlands, wastewater treatment plants (WWTPs) and stream channels, and a TN model was calibrated that included inputs from agriculture, WWTPs and atmospheric deposition. At the RARB outlet, downstream from Winnipeg, Manitoba, the majority of the delivered TP and TN came from the Red River Basin (90%), followed by the Upper Assiniboine River and Souris River basins. Agriculture was the single most important TP and TN source for each major basin, province and state. In general, stream channels (historically deposited nutrients and from bank erosion) were the second most important source of TP. Performance metrics for the RARB SPARROW model are similarly robust compared to other, larger US SPARROW models making it a potentially useful tool to address questions of where nutrients originate and their relative contributions to loads delivered to Lake Winnipeg.

  11. Modeling Aircraft Wing Loads from Flight Data Using Neural Networks

    Science.gov (United States)

    Allen, Michael J.; Dibley, Ryan P.

    2003-01-01

    Neural networks were used to model wing bending-moment loads, torsion loads, and control surface hinge-moments of the Active Aeroelastic Wing (AAW) aircraft. Accurate loads models are required for the development of control laws designed to increase roll performance through wing twist while not exceeding load limits. Inputs to the model include aircraft rates, accelerations, and control surface positions. Neural networks were chosen to model aircraft loads because they can account for uncharacterized nonlinear effects while retaining the capability to generalize. The accuracy of the neural network models was improved by first developing linear loads models to use as starting points for network training. Neural networks were then trained with flight data for rolls, loaded reversals, wind-up-turns, and individual control surface doublets for load excitation. Generalization was improved by using gain weighting and early stopping. Results are presented for neural network loads models of four wing loads and four control surface hinge moments at Mach 0.90 and an altitude of 15,000 ft. An average model prediction error reduction of 18.6 percent was calculated for the neural network models when compared to the linear models. This paper documents the input data conditioning, input parameter selection, structure, training, and validation of the neural network models.

  12. Modelling human eye under blast loading.

    Science.gov (United States)

    Esposito, L; Clemente, C; Bonora, N; Rossi, T

    2015-01-01

    Primary blast injury (PBI) is the general term that refers to injuries resulting from the mere interaction of a blast wave with the body. Although few instances of primary ocular blast injury, without a concomitant secondary blast injury from debris, are documented, some experimental studies demonstrate its occurrence. In order to investigate PBI to the eye, a finite element model of the human eye using simple constitutive models was developed. The material parameters were calibrated by a multi-objective optimisation performed on available eye impact test data. The behaviour of the human eye and the dynamics of mechanisms occurring under PBI loading conditions were modelled. For the generation of the blast waves, different combinations of explosive (trinitrotoluene) mass charge and distance from the eye were analysed. An interpretation of the resulting pressure, based on the propagation and reflection of the waves inside the eye bulb and orbit, is proposed. The peculiar geometry of the bony orbit (similar to a frustum cone) can induce a resonance cavity effect and generate a pressure standing wave potentially hurtful for eye tissues.

  13. Spatial distribution and assessment of nutrient pollution in Lake Toba using 2D-multi layers hydrodynamic model and DPSIR framework

    Science.gov (United States)

    Sunaryani, A.; Harsono, E.; Rustini, H. A.; Nomosatryo, S.

    2018-02-01

    Lake Toba is the largest lake in Indonesia utilized as a source of life-support for drinking and clean water, energy sources, aquaculture and tourism. Nowadays the water quality in Lake Toba has decreased due to the presence of excessive nutrient (nitrogen: N and phosphorus: P). This study aims to describe the spatial distribution of nutrient pollution and to develop a decision support tool for the identification and evaluation of nutrient pollution control in Lake Toba. Spatial distribution method was conducted by 2D-multi layers hydrodynamic model, while DPSIR Framework is used as a tool for the assessment. The results showed that the concentration of nutrient was low and tended to increase along the water depth, but nutrient concentration in aquaculture zones was very high and the trophic state index has reached eutrophic state. The principal anthropogenic driving forces were population growth and the development of aquaculture, livestock, agriculture, and tourism. The main environmental pressures showed that aquaculture and livestock waste are the most important nutrient sources (93% of N and 87% of P loads). State analysis showed that high nutrient concentration and increased algal growth lead to oxygen depletion. The impacts of these conditions were massive fish kills, loss of amenities and tourism value, also decreased usability of clean water supply. This study can be a useful information for decision-makers to evaluate nutrient pollution control. Nutrient pollution issue in Lake Toba requires the attention of local government and public society to maintain its sustainability.

  14. Multivariate Modelling of Extreme Load Combinations for Wind Turbines

    DEFF Research Database (Denmark)

    Dimitrov, Nikolay Krasimirov

    2015-01-01

    We demonstrate a model for estimating the joint probability distribution of two load components acting on a wind turbine blade cross section. The model addresses the problem of modelling the probability distribution of load time histories with large periodic components by dividing the signal...... into a periodic part and a perturbation term, where each part has a known probability distribution. The proposed model shows good agreement with simulated data under stationary conditions, and a design load envelope based on this model is comparable to the load envelope estimated using the standard procedure...... for determining contemporaneous loads. By defining a joint probability distribution and full return-period contours for multiple load components, the suggested procedure gives the possibility for determining the most critical loading direction in a blade cross section, or for carrying out reliability analysis...

  15. Using AnnAGNPS to Predict the Effects of Tile Drainage Control on Nutrient and Sediment Loads for a River Basin.

    Science.gov (United States)

    Que, Z; Seidou, O; Droste, R L; Wilkes, G; Sunohara, M; Topp, E; Lapen, D R

    2015-03-01

    Controlled tile drainage (CTD) can reduce pollutant loading. The Annualized Agricultural Nonpoint Source model (AnnAGNPS version 5.2) was used to examine changes in growing season discharge, sediment, nitrogen, and phosphorus loads due to CTD for a ∼3900-km agriculturally dominated river basin in Ontario, Canada. Two tile drain depth scenarios were examined in detail to mimic tile drainage control for flat cropland: 600 mm depth (CTD) and 200 mm (CTD) depth below surface. Summed for five growing seasons (CTD), direct runoff, total N, and dissolved N were reduced by 6.6, 3.5, and 13.7%, respectively. However, five seasons of summed total P, dissolved P, and total suspended solid loads increased as a result of CTD by 0.96, 1.6, and 0.23%. The AnnAGNPS results were compared with mass fluxes observed from paired experimental watersheds (250, 470 ha) in the river basin. The "test" experimental watershed was dominated by CTD and the "reference" watershed by free drainage. Notwithstanding environmental/land use differences between the watersheds and basin, comparisons of seasonal observed and predicted discharge reductions were comparable in 100% of respective cases. Nutrient load comparisons were more consistent for dissolved, relative to particulate water quality endpoints. For one season under corn crop production, AnnAGNPS predicted a 55% decrease (CTD) in dissolved N from the basin. AnnAGNPS v. 5.2 treats P transport from a surface pool perspective, which is appropriate for many systems. However, for assessment of tile drainage management practices for relatively flat tile-dominated systems, AnnAGNPS may benefit from consideration of P and particulate transport in the subsurface. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  16. Is Recovery of Large-Bodied Zooplankton after Nutrient Loading Reduction Hampered by Climate Warming? A Long-Term Study of Shallow Hypertrophic Lake Sobygaard, Denmark

    DEFF Research Database (Denmark)

    Florencia Gutierrez, Maria; Devercelli, Melina; Brucet Balmana, Sandra

    2016-01-01

    Nutrient fluctuations and climate warming can synergistically affect trophic dynamics in lakes, resulting in enhanced symptoms of eutrophication, thereby potentially counteracting restoration measures. We performed a long-term study (23 years) of zooplankton in Danish Lake Sobygaard, which...... is in recovery after nutrient loading reduction, but now faces the effects of climate warming. We hypothesized that the recovery of large-bodied zooplankton after nutrient loading reduction would be hampered by climate warming through indirect effects on fish size structure. We found a shift in macrozooplankton...... from initial dominance of Daphnia spp. towards Bosmina spp. as well as a decline in the body size of copepods and an increase in the abundance of nauplii. These changes coincided with the increase in small sized fish as a result of rising water temperature. Despite a reduction in body size, the total...

  17. Determination of aggregated load power consumption, under non-sinusoidal supply using an improved load model

    International Nuclear Information System (INIS)

    Bagheri, R.; Moghani, J.S.; Gharehpetian, G.B.; Mirtalaei, S.M.M.

    2009-01-01

    The harmonic content of supply voltage results in additional power losses and hence increases the load power consumption. The role of the power quality equipments on the power consumption without using an accurate model cannot be determined, too. In this paper, an improved model for aggregated loads proposed, which estimates the effects of voltage harmonics on the power consumption. The distinguished aspect of the proposed model is its parameters identification method which is based on the practical techniques, such as employing a capacitor bank or varying dummy loads in steps. The proposed model has been verified by the comparison of measured and simulated results.

  18. Modelling C allocation in response to nutrient availability

    Science.gov (United States)

    Stocker, Benjamin; Prentice, Colin

    2015-04-01

    Carbon (C) allocation in ecosystems is a key variable of the global terrestrial C cycle. While photosynthesis governs the amount of C that enters ecosystems, its subsequent allocation to compartments with different life times determines its over-all residence time and variations in allocation patterns drive changes in ecosystem C balance and its response to environmental change. A better understanding of the controls on allocation is thus key to improving global vegetation models that commonly rely on using fixed partitioning factors. Observational data suggests variations of ecosystem structure and functioning along large-scale gradients of resource availability. Below-ground C allocation, inferred as gross primary production minus above-ground biomass production increases along gradients of decreasing nutrient availability. This is not only due to more root growth, but also due to enhanced production of exudates and stimulation of root symbionts and has been interpreted to reflect optimal plant allocation decisions under a varying soil fertility status. Here, we propose a model that accounts for trade-offs between (i) growth in above-ground and (ii) below-ground plant compartments, (iii) exudation to the rhizosphere and root symbionts and (iv) temporary storage in non-structural pools. By postulating the maximization of long-term growth under a given (seasonal regime) of soil nitrogen (N) availability, we attempt to reproduce observed large-scale gradients. The model is formulated based on a C cost for different N uptake decisions, where the cost is a function of N availability, root mass, and soil temperature (for biological N fixation). On a daily time scale, ecosystem N uptake may be realized by C exudation to the rhizosphere and/or symbiotic fixation of atmospheric N2. On an annual time scale, allocation to roots versus leaves is adjusted to soil inorganic N availability and modeled to yield maximum total growth. Exudation versus temporary storage of C is

  19. Water quality assessment and catchment-scale nutrient flux modeling in the Ramganga River Basin in north India: An application of INCA model.

    Science.gov (United States)

    Pathak, Devanshi; Whitehead, Paul G; Futter, Martyn N; Sinha, Rajiv

    2018-03-07

    The present study analyzes the water quality characteristics of the Ramganga (a major tributary of the Ganga river) using long-term (1991-2009) monthly data and applies the Integrated Catchment Model of Nitrogen (INCA-N) and Phosphorus (INCA-P) to the catchment. The models were calibrated and validated using discharge (1993-2011), phosphate (1993-2010) and nitrate (2007-2010) concentrations. The model results were assessed based on Pearson's correlation, Nash-Sutcliffe and Percentage bias statistics along with a visual inspection of the outputs. The seasonal variation study shows high nutrient concentrations in the pre-monsoon season compared to the other seasons. High nutrient concentrations in the low flows period pose a serious threat to aquatic life of the river although the concentrations are lowered during high flows because of the dilution effect. The hydrological model is satisfactorily calibrated with R 2 and NS values ranging between 0.6-0.8 and 0.4-0.8, respectively. INCA-N and INCA-P successfully capture the seasonal trend of nutrient concentrations with R 2 >0.5 and PBIAS within ±17% for the monthly averages. Although, high concentrations are detected in the low flows period, around 50% of the nutrient load is transported by the monsoonal high flows. The downstream catchments are characterized by high nutrient transport through high flows where additional nutrient supply from industries and agricultural practices also prevail. The seasonal nitrate (R 2 : 0.88-0.94) and phosphate (R 2 : 0.62-0.95) loads in the catchment are calculated using model results and ratio estimator load calculation technique. On average, around 548tonnes of phosphorus (as phosphate) and 77,051tonnes of nitrogen (as nitrate) are estimated to be exported annually from the Ramganga River to the Ganga. Overall, the model has been able to successfully reproduce the catchment dynamics in terms of seasonal variation and broad-scale spatial variability of nutrient fluxes in the

  20. Nutrient Loading Impacts on Culturable E. coli and other Heterotrophic Bacteria Fate in Simulated Stream Mesocosms

    Science.gov (United States)

    Understanding fecal indicator bacteria persistence in aquatic environments is important when making management decisions to improve instream water quality. Routinely, bacteria fate and transport models that rely on published kinetic decay constants are used to inform such decision making. The object...

  1. Spatial optimization of watershed management practices for nitrogen load reduction using a modeling-optimization framework.

    Science.gov (United States)

    Yang, Guoxiang; Best, Elly P H

    2015-09-15

    Best management practices (BMPs) can be used effectively to reduce nutrient loads transported from non-point sources to receiving water bodies. However, methodologies of BMP selection and placement in a cost-effective way are needed to assist watershed management planners and stakeholders. We developed a novel modeling-optimization framework that can be used to find cost-effective solutions of BMP placement to attain nutrient load reduction targets. This was accomplished by integrating a GIS-based BMP siting method, a WQM-TMDL-N modeling approach to estimate total nitrogen (TN) loading, and a multi-objective optimization algorithm. Wetland restoration and buffer strip implementation were the two BMP categories used to explore the performance of this framework, both differing greatly in complexity of spatial analysis for site identification. Minimizing TN load and BMP cost were the two objective functions for the optimization process. The performance of this framework was demonstrated in the Tippecanoe River watershed, Indiana, USA. Optimized scenario-based load reduction indicated that the wetland subset selected by the minimum scenario had the greatest N removal efficiency. Buffer strips were more effective for load removal than wetlands. The optimized solutions provided a range of trade-offs between the two objective functions for both BMPs. This framework can be expanded conveniently to a regional scale because the NHDPlus catchment serves as its spatial computational unit. The present study demonstrated the potential of this framework to find cost-effective solutions to meet a water quality target, such as a 20% TN load reduction, under different conditions. Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. Long-term modelling of nitrogen turnover and critical loads in a forested catchment using the INCA model

    Directory of Open Access Journals (Sweden)

    J.-J. Langusch

    2002-01-01

    Full Text Available Many forest ecosystems in Central Europe have reached the status of N saturation due to chronically high N deposition. In consequence, the NO3 leaching into ground- and surface waters is often substantial. Critical loads have been defined to abate the negative consequences of the NO3 leaching such as soil acidification and nutrient losses. The steady state mass balance method is normally used to calculate critical loads for N deposition in forest ecosystems. However, the steady state mass balance approach is limited because it does not take into account hydrology and the time until the steady state is reached. The aim of this study was to test the suitability of another approach: the dynamic model INCA (Integrated Nitrogen Model for European Catchments. Long-term effects of changing N deposition and critical loads for N were simulated using INCA for the Lehstenbach spruce catchment (Fichtelgebirge, NE Bavaria, Germany under different hydrological conditions. Long-term scenarios of either increasing or decreasing N deposition indicated that, in this catchment, the response of nitrate concentrations in runoff to changing N deposition is buffered by a large groundwater reservoir. The critical load simulated by the INCA model with respect to a nitrate concentration of 0.4 mg N l–1 as threshold value in runoff was 9.7 kg N ha–1yr–1 compared to 10 kg ha–1yr–1 for the steady state model. Under conditions of lower precipitation (520 mm the resulting critical load was 7.7 kg N ha–1yr–1 , suggesting the necessity to account for different hydrological conditions when calculating critical loads. The INCA model seems to be suitable to calculate critical loads for N in forested catchments under varying hydrological conditions e.g. as a consequence of climate change. Keywords: forest ecosystem, N saturation, critical load, modelling, long-term scenario, nitrate leaching, critical loads reduction, INCA

  3. Modeling of Closed-Die Forging for Estimating Forging Load

    Science.gov (United States)

    Sheth, Debashish; Das, Santanu; Chatterjee, Avik; Bhattacharya, Anirban

    2017-02-01

    Closed die forging is one common metal forming process used for making a range of products. Enough load is to exert on the billet for deforming the material. This forging load is dependent on work material property and frictional characteristics of the work material with the punch and die. Several researchers worked on estimation of forging load for specific products under different process variables. Experimental data on deformation resistance and friction were used to calculate the load. In this work, theoretical estimation of forging load is made to compare this value with that obtained through LS-DYNA model facilitating the finite element analysis. Theoretical work uses slab method to assess forging load for an axi-symmetric upsetting job made of lead. Theoretical forging load estimate shows slightly higher value than the experimental one; however, simulation shows quite close matching with experimental forging load, indicating possibility of wide use of this simulation software.

  4. Inserting Ecological Detail into Economic Analysis: Agricultural Nutrient Loading of an Estuary Fishery

    Directory of Open Access Journals (Sweden)

    John Tschirhart

    2011-09-01

    Full Text Available Linked general equilibrium economic and ecological models are connected through agricultural runoff and the fisheries. They are applied to a North Carolina estuary in which agricultural runoff alters phytoplankton densities and the resulting hypoxia leads to diminished fisheries. The effects of hypoxia on multiple species across space are analyzed and the joint economic and ecosystem wide response to a policy of reduced runoff is quantified. The approach provides an assessment of changes in ecological welfare (in terms of species populations and economic welfare (in terms of equivalent variations following reductions in runoff.

  5. Use of Nutrient Balances in Comprehensive Watershed Water Quality Modeling of Chesapeake Bay

    National Research Council Canada - National Science Library

    Donigian, Anthony

    1998-01-01

    ... state of-the-art watershed modeling capability that includes detailed soil process simulation for agricultural areas, linked to an instream water quality and nutrient model capable of representing...

  6. Changes in the location of biodiversity-ecosystem function hot spots across the seafloor landscape with increasing sediment nutrient loading.

    Science.gov (United States)

    Thrush, Simon F; Hewitt, Judi E; Kraan, Casper; Lohrer, A M; Pilditch, Conrad A; Douglas, Emily

    2017-04-12

    Declining biodiversity and loss of ecosystem function threatens the ability of habitats to contribute ecosystem services. However, the form of the relationship between biodiversity and ecosystem function (BEF) and how relationships change with environmental change is poorly understood. This limits our ability to predict the consequences of biodiversity loss on ecosystem function, particularly in real-world marine ecosystems that are species rich, and where multiple ecosystem functions are represented by multiple indicators. We investigated spatial variation in BEF relationships across a 300 000 m 2 intertidal sandflat by nesting experimental manipulations of sediment pore water nitrogen concentration into sites with contrasting macrobenthic community composition. Our results highlight the significance of many different elements of biodiversity associated with environmental characteristics, community structure, functional diversity, ecological traits or particular species (ecosystem engineers) to important functions of coastal marine sediments (benthic oxygen consumption, ammonium pore water concentrations and flux across the sediment-water interface). Using the BEF relationships developed from our experiment, we demonstrate patchiness across a landscape in functional performance and the potential for changes in the location of functional hot and cold spots with increasing nutrient loading that have important implications for mapping and predicating change in functionality and the concomitant delivery of ecosystem services. © 2017 The Author(s).

  7. Modeling nutrient flows in the food chain of China.

    Science.gov (United States)

    Ma, L; Ma, W Q; Velthof, G L; Wang, F H; Qin, W; Zhang, F S; Oenema, O

    2010-01-01

    Increasing nitrogen (N) and phosphorus (P) inputs have greatly contributed to the increasing food production in China during the last decades, but have also increased N and P losses to the environment. The pathways and magnitude of these losses are not well quantified. Here, we report on N and P use efficiencies and losses at a national scale in 2005, using the model NUFER (NUtrient flows in Food chains, Environment and Resources use). Total amount of "new" N imported to the food chain was 48.8 Tg in 2005. Only 4.4.Tg reached households as food. Average N use efficiencies in crop production, animal production, and the whole food chain were 26, 11, and 9%, respectively. Most of the imported N was lost to the environment, that is, 23 Tg N to atmosphere, as ammonia (57%), nitrous oxide (2%), dinitrogen (33%), and nitrogen oxides (8%), and 20 Tg to waters. The total P input into the food chain was 7.8 Tg. The average P use efficiencies in crop production, animal production, and the whole food chain were 36, 5, and 7%, respectively. This is the first comprehensive overview of N and P balances, losses, and use efficiencies of the food chain in China. It shows that the N and P costs of food are high (for N 11 kg kg(-1), for P 13 kg kg(-1)). Key measures for lowering the N and P costs of food production are (i) increasing crop and animal production, (ii) balanced fertilization, and (iii) improved manure management.

  8. A dynamic growth model for prediction of nutrient partitioning and manure production in growing–finishing pigs: Model development and evaluation

    DEFF Research Database (Denmark)

    Danfær, Allan Christian; Jørgensen, Henry; Kebreab, E

    2015-01-01

    minor mean bias. Root mean square prediction error (RMSPE) was used in evaluation of the model for its predictive power. The overall RMSPE was 2.2 and 4.1 g/d for protein and lipid deposition, respectively. The excretion database used for evaluation of the model was constructed from 150 digestibility...... data and then with excretion data. The data had 48 different feeding regimes with contrasting energy and lysine intakes at 2 different stages of growth. The overall observed and predicted mean were 109 and 112 g/d for protein deposition and 132 and 136 g/d for lipid deposition respectively, suggesting......Nutrient loading and air emissions from swine operations raise environmental concerns. The objective of the study was to describe and evaluate a mathematical model (Davis Swine Model) of nutrient partitioning and predict manure excretion and composition on a daily basis. State variables...

  9. Is Recovery of Large-Bodied Zooplankton after Nutrient Loading Reduction Hampered by Climate Warming? A Long-Term Study of Shallow Hypertrophic Lake Søbygaard, Denmark

    Directory of Open Access Journals (Sweden)

    María Florencia Gutierrez

    2016-08-01

    Full Text Available Nutrient fluctuations and climate warming can synergistically affect trophic dynamics in lakes, resulting in enhanced symptoms of eutrophication, thereby potentially counteracting restoration measures. We performed a long-term study (23 years of zooplankton in Danish Lake Søbygaard, which is in recovery after nutrient loading reduction, but now faces the effects of climate warming. We hypothesized that the recovery of large-bodied zooplankton after nutrient loading reduction would be hampered by climate warming through indirect effects on fish size structure. We found a shift in macrozooplankton from initial dominance of Daphnia spp. towards Bosmina spp. as well as a decline in the body size of copepods and an increase in the abundance of nauplii. These changes coincided with the increase in small sized fish as a result of rising water temperature. Despite a reduction in body size, the total biomass of cladocerans increased coinciding with a diminished fish catch per unit effort (CPUE, and likely then an overall reduction in the predation on zooplankton. A cascading effect to phytoplankton was evidenced by enhanced zooplankton:phytoplankton and cladoceran:phytoplankton ratios and a decrease in Chl-a:TP and Chl-a:TN ratios. Our results indicate that climate warming, through changes in the size structure of fish community, has major effects on zooplankton size structure. In Lake Søbygaard, the decline in zooplankton size did not prevent, but modulated, the positive cascading effect on phytoplankton through an expected diminished fish CPUE related to nutrient loading reduction.

  10. Phytoplankton biomass and composition in a well-flushed, sub-tropical estuary: The contrasting effects of hydrology, nutrient loads and allochthonous influences.

    Science.gov (United States)

    Hart, J A; Phlips, E J; Badylak, S; Dix, N; Petrinec, K; Mathews, A L; Green, W; Srifa, A

    2015-12-01

    The primary objective of this study was to examine trends in phytoplankton biomass and species composition under varying nutrient load and hydrologic regimes in the Guana Tolomato Matanzas estuary (GTM), a well-flushed sub-tropical estuary located on the northeast coast of Florida. The GTM contains both regions of significant human influence and pristine areas with only modest development, providing a test case for comparing and contrasting phytoplankton community dynamics under varying degrees of nutrient load. Water temperature, salinity, Secchi disk depth, nutrient concentrations and chlorophyll concentrations were determined on a monthly basis from 2002 to 2012 at three representative sampling sites in the GTM. In addition, microscopic analyses of phytoplankton assemblages were carried out monthly for a five year period from 2005 through 2009 at all three sites. Results of this study indicate that phytoplankton biomass and composition in the GTM are strongly influenced by hydrologic factors, such as water residence times and tidal exchanges of coastal waters, which in turn are affected by shifts in climatic conditions, most prominently rainfall levels. These influences are exemplified by the observation that the region of the GTM with the longest water residence times but lowest nutrient loads exhibited the highest phytoplankton peaks of autochthonous origin. The incursion of a coastal bloom of the toxic dinoflagellate Karenia brevis into the GTM in 2007 demonstrates the potential importance of allochthonous influences on the ecosystem. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Recent Advances in Modeling Phosphorus and Nitrogen Delivery to the Gulf of Mexico and Implications for Managing Nutrients n the Mississippi River Basin

    Science.gov (United States)

    Alexander, R. B.; Smith, R. A.; Schwarz, G. E.; Boyer, E. W.; Nolan, J. V.; Brakebill, J. W.

    2008-12-01

    Although the increased availability of reactive nutrients in past decades has benefited society via food and energy production, the corresponding rise in nutrient loadings to aquatic ecosystems is of particular concern, especially in many estuaries globally where increased nutrient loads have contributed to eutrophic conditions. In the United States, elevated riverine nutrients have contributed to stressed trophic conditions in a majority of estuaries, including the shallow coastal waters of the Louisiana shelf in the northern Gulf of Mexico, where both nitrogen and phosphorus loadings are recognized as contributing to seasonal hypoxic conditions. Advances in geospatial modeling of nitrogen and phosphorus sources and transport in the Mississippi and Atchafalaya River Basins (MARB), as reported in a recent U.S. Geological Survey (USGS) study, provide important information to support improved assessments and management of nutrient loadings to the northern Gulf of Mexico. We summarize the findings of this study and discuss the implications for managing nutrient sources in the MARB. The study reveals important differences in the sources and aquatic transport of nitrogen and phosphorus that affect delivery to the Gulf. Although agricultural sources contribute a majority of the delivered nutrients to the Gulf, corn and soybean cultivation is the largest contributor of nitrogen whereas phosphorus originates primarily from animal manure on pasture and rangelands. Atmospheric deposition is the second leading source of nitrogen, with urban sources contributing relatively small quantities of both nutrients. Furthermore, we find that both nitrogen and phosphorus delivery to the Gulf is controlled by hydrological and biogeochemical processes (e.g., water travel time, denitrification, storage) that scale with stream size, although phosphorus also displays large local- and regional-scale differences in delivery caused by reservoir trapping. The importance of these processes

  12. Changes in distributional patterns of plaice Pleuronectes platessa in the central and eastern North Sea; do declining nutrient loadings play a role?

    Science.gov (United States)

    Støttrup, Josianne G.; Munk, Peter; Kodama, Masashi; Stedmon, Colin

    2017-09-01

    Since the beginning of the 1990s, there has been a change in the relative distribution of smaller age-classes of plaice Pleuronectes platessa (age 1-3) in the North Sea. The abundances have increased in deeper, more offshore areas, while coastal abundances have been stagnant or declining. For the same time period available time series data on nutrient conditions in the coastal North Sea area show that the freshwater nitrogen loading has decreased by about 50%. While nutrient concentrations in the ambient environment have been shown to influence growth in juvenile plaice through influence on their prey, we here inspect the potential linkage between distributional changes in plaice and the decline in nutrient loading. We compare plaice observations in coastal areas in the eastern North Sea, which have experienced large changes in eutrophication, with observations for the Dogger Bank, a large sandbank in a shallow offshore area of the North Sea. The Dogger Bank, was used as a reference location assuming this area has been less influenced from coastal eutrophication but similar regional climate conditions, and here we found no changes in the abundances of juvenile plaice. The increase in the use of offshore habitats as nursery areas by juvenile plaice in the North Sea appears not related to water depth per se but driven by specific processes dominating in near-shore areas and may be related to changes in nutrient loadings. This point to the importance of separating more general depth-related factors from conditions specific for near-shore areas, such as nutrient loadings in coastal waters and export offshore. The concurrent changes in environment and in distribution of juvenile plaice may have implications for environmental and fisheries management.

  13. Scientific and technical advisory committee review of the nutrient inputs to the watershed model

    Science.gov (United States)

    The following is a report by a STAC Review Team concerning the methods and documentation used by the Chesapeake Bay Partnership for evaluation of nutrient inputs to Phase 6 of the Chesapeake Bay Watershed Model. The “STAC Review of the Nutrient Inputs to the Watershed Model” (previously referred to...

  14. 101 Modelling and Forecasting Periodic Electric Load for a ...

    African Journals Online (AJOL)

    User

    2012-01-24

    Jan 24, 2012 ... Key words: Electric-load, Linear trend, Compound-growth, Cubic model, ... Static state estimation method, the Gaussian Process models, time ... specific variables, the independent and dependent variables. Y is load at a given year X, it states that, Y = a+ bX where a and b can be obtained from equation (1).

  15. Modelling concept of lettuce breeding for nutrient efficiency

    NARCIS (Netherlands)

    Kerbiriou, P.J.; Stomph, T.J.; Lammerts Van Bueren, E.; Struik, P.C.

    2014-01-01

    Modern lettuce cultivars are bred for use under high levels of input of water and nutrients, and therefore less adapted to low-input or organic conditions in which nitrate availability varies over time and within the soil profile. To create robust cultivars it is necessary to assess which traits

  16. Cyclic Loading of Growing Tissue in a Bioreactor: Mathematical Model and Asymptotic Analysis

    KAUST Repository

    Pohlmeyer, J. V.

    2013-10-24

    A simplified 2D mathematical model for tissue growth within a cyclically-loaded tissue engineering scaffold is presented and analyzed. Such cyclic loading has the potential to improve yield and functionality of tissue such as bone and cartilage when grown on a scaffold within a perfusion bioreactor. The cyclic compression affects the flow of the perfused nutrient, leading to flow properties that are inherently unsteady, though periodic, on a timescale short compared with that of tissue proliferation. A two-timescale analysis based on these well-separated timescales is exploited to derive a closed model for the tissue growth on the long timescale of proliferation. Some sample numerical results are given for the final model, and discussed. © 2013 Society for Mathematical Biology.

  17. Modeling nutrient in-stream processes at the watershed scale using Nutrient Spiralling metrics

    OpenAIRE

    R. Marcé; J. Armengol

    2009-01-01

    One of the fundamental problems of using large-scale biogeochemical models is the uncertainty involved in aggregating the components of fine-scale deterministic models in watershed applications, and in extrapolating the results of field-scale measurements to larger spatial scales. Although spatial or temporal lumping may reduce the problem, information obtained during fine-scale research may not apply to lumped categories. Thus, the use of knowledge gained through fine-scale studies to predic...

  18. Load Composition Model Workflow (BPA TIP-371 Deliverable 1A)

    Energy Technology Data Exchange (ETDEWEB)

    Chassin, David P.; Cezar, Gustavo V.; /SLAC

    2017-07-17

    This project is funded under Bonneville Power Administration (BPA) Strategic Partnership Project (SPP) 17-005 between BPA and SLAC National Accelerator Laboratory. The project in a BPA Technology Improvement Project (TIP) that builds on and validates the Composite Load Model developed by the Western Electric Coordinating Council's (WECC) Load Modeling Task Force (LMTF). The composite load model is used by the WECC Modeling and Validation Work Group to study the stability and security of the western electricity interconnection. The work includes development of load composition data sets, collection of load disturbance data, and model development and validation. This work supports reliable and economic operation of the power system. This report was produced for Deliverable 1A of the BPA TIP-371 Project entitled \\TIP 371: Advancing the Load Composition Model". The deliverable documents the proposed work ow for the Composite Load Model, which provides the basis for the instrumentation, data acquisition, analysis and data dissemination activities addressed by later phases of the project.

  19. Modeling electricity loads in California: a continuous-time approach

    Science.gov (United States)

    Weron, R.; Kozłowska, B.; Nowicka-Zagrajek, J.

    2001-10-01

    In this paper we address the issue of modeling electricity loads and prices with diffusion processes. More specifically, we study models which belong to the class of generalized Ornstein-Uhlenbeck processes. After comparing properties of simulated paths with those of deseasonalized data from the California power market and performing out-of-sample forecasts we conclude that, despite certain advantages, the analyzed continuous-time processes are not adequate models of electricity load and price dynamics.

  20. Scaling Dissolved Nutrient Removal in River Networks: A Comparative Modeling Investigation

    Science.gov (United States)

    Ye, Sheng; Reisinger, Alexander J.; Tank, Jennifer L.; Baker, Michelle A.; Hall, Robert O.; Rosi, Emma J.; Sivapalan, Murugesu

    2017-11-01

    Along the river network, water, sediment, and nutrients are transported, cycled, and altered by coupled hydrological and biogeochemical processes. Our current understanding of the rates and processes controlling the cycling and removal of dissolved inorganic nutrients in river networks is limited due to a lack of empirical measurements in large, (nonwadeable), rivers. The goal of this paper was to develop a coupled hydrological and biogeochemical process model to simulate nutrient uptake at the network scale during summer base flow conditions. The model was parameterized with literature values from headwater streams, and empirical measurements made in 15 rivers with varying hydrological, biological, and topographic characteristics, to simulate nutrient uptake at the network scale. We applied the coupled model to 15 catchments describing patterns in uptake for three different solutes to determine the role of rivers in network-scale nutrient cycling. Model simulation results, constrained by empirical data, suggested that rivers contributed proportionally more to nutrient removal than headwater streams given the fraction of their length represented in a network. In addition, variability of nutrient removal patterns among catchments was varied among solutes, and as expected, was influenced by nutrient concentration and discharge. Net ammonium uptake was not significantly correlated with any environmental descriptor. In contrast, net daily nitrate removal was linked to suspended chlorophyll a (an indicator of primary producers) and land use characteristics. Finally, suspended sediment characteristics and agricultural land use were correlated with net daily removal of soluble reactive phosphorus, likely reflecting abiotic sorption dynamics. Rivers are understudied relative to streams, and our model suggests that rivers can contribute more to network-scale nutrient removal than would be expected based upon their representative fraction of network channel length.

  1. Modified bond model for shear in slabs under concentrated loads

    NARCIS (Netherlands)

    Lantsoght, E.O.L.; Van der Veen, C.; De Boer, A.

    2015-01-01

    Slabs subjected to concentrated loads close to supports, as occurring for truck loads on slab bridges, are less studied than beams in shear or slab-column connections in punching. To predict the shear capacity for this case, the Bond Model for concentric punching shear was studied initially.

  2. A Workflow to Model Microbial Loadings in Watersheds

    Science.gov (United States)

    Many watershed models simulate overland and instream microbial fate and transport, but few actually provide loading rates on land surfaces and point sources to the water body network. This paper describes the underlying general equations for microbial loading rates associated wit...

  3. A Workflow to Model Microbial Loadings in Watersheds (proceedings)

    Science.gov (United States)

    Many watershed models simulate overland and instream microbial fate and transport, but few actually provide loading rates on land surfaces and point sources to the water body network. This paper describes the underlying general equations for microbial loading rates associated wit...

  4. A dynamic growth model for prediction of nutrient partitioning and manure production in growing-finishing pigs: Model development and evaluation.

    Science.gov (United States)

    Strathe, A B; Danfær, A; Jørgensen, H; Kebreab, E

    2015-03-01

    Nutrient loading and air emissions from swine operations raise environmental concerns. The objective of the study was to describe and evaluate a mathematical model (Davis Swine Model) of nutrient partitioning and predict manure excretion and composition on a daily basis. State variables of the model were AA, fatty acids, and a central pool of metabolites that supplied substrate for lipid synthesis and oxidation. The model traced the fate of ingested nutrients and water through digestion and intermediary metabolism into body protein, fat, water, and ash, where body protein and fat represented the body constituent pools. It was assumed that fluxes of metabolites follow saturation kinetics, depending on metabolite concentrations. The main inputs to the model were diet nutrient composition, feed intake, water-to-feed ratio, and initial BW. First, the model was challenged with nutrient partitioning data and then with excretion data. The data had 48 different feeding regimes with contrasting energy and lysine intakes at 2 different stages of growth. The overall observed and predicted mean were 109 and 112 g/d for protein deposition and 132 and 136 g/d for lipid deposition respectively, suggesting minor mean bias. Root mean square prediction error (RMSPE) was used in evaluation of the model for its predictive power. The overall RMSPE was 2.2 and 4.1 g/d for protein and lipid deposition, respectively. The excretion database used for evaluation of the model was constructed from 150 digestibility trials using growing-finishing pig diets that had a wide range of nutrient chemical composition. Nutrient and water excretion were quantified using the principle of mass conservation. The average daily observed and predicted manure production was 3.79 and 3.99 kg/d, respectively, with a RMSPE of 0.49 kg/d. There was a good agreement between observed and predicted mean fecal N output (9.9 and 9.8 g/d, respectively). Similarly, the overall observed and predicted mean urine N output

  5. A model set-up for an oxygen and nutrient flux model for Aarhus Bay (Denmark)

    DEFF Research Database (Denmark)

    Fossing, H.; Berg, P.; Thamdrup, B.

    . They also produce a number of waste products, such as hydrogen sulphide, that have a great impact on the marine environment. After many years of research, our knowledge of the processes going on in the seabed is substantial. This knowledge forms the basis of a new mathematical model linking the complex...... material cycles taking place in the seabed and describing the exchange of oxygen and nutrients between seabed and seawater. The construction of the model is described in this report. This report was prepared as a contribution towards developing NERI’s expertise within the field of mathematical modelling....

  6. A Dynamic Model for Load Balancing in Cloud Infrastructure

    Directory of Open Access Journals (Sweden)

    Jitendra Bhagwandas Bhatia

    2015-08-01

    Full Text Available This paper analysis various challenges faced in optimizing computing resource utilization via load balancing and presents a platform-independent model for load balancing which targets high availability of resources, low SLA (Service Level agreement violations and saves power. To achieve this, incoming requests are monitored for sudden burst, a prediction model is employed to maintain high availability and a power-aware algorithm is applied for choosing a suitable physical node for a virtual host. The proposed dynamic load balancing model provides a way to conflicting goals of saving power and maintaining high resource availability.For anyone building a private, public or hybrid IaaS cloud infrastructure, load balancing of virtual hosts on a limited number of physical nodes, becomes a crucial aspect. This paper analysis various challenges faced in optimizing computing resource utilization via load balancing and presents a platform independent model for load balancing which targets high availability of resources, low SLA (Service Level agreement violations and saves power. To achieve this, incoming requests are monitored for sudden burst, prediction model is employed to maintain high availability and power aware algorithm is applied for choosing a suitable physical node for virtual host. The proposed dynamic load balancing model provides a way to conflicting goals of saving power and maintaining high resource availability.

  7. Groundwater impact on surface water quality and nutrient loads in lowland polder catchments: monitoring the greater Amsterdam area

    NARCIS (Netherlands)

    Yu, L.; Rozemeijer, J.; Breukelen, B.M. van; Ouboter, M.; Vlugt, C. van der; Broers, H.P.

    2018-01-01

    The Amsterdam area, a highly manipulated delta area formed by polders and reclaimed lakes, struggles with high nutrient levels in its surface water system. The polders receive spatially and temporally variable amounts of water and nutrients via surface runoff, groundwater seepage, sewer leakage, and

  8. Groundwater impacts on surface water quality and nutrient loads in lowland polder catchments : Monitoring the greater Amsterdam area

    NARCIS (Netherlands)

    Yu, Liang; Rozemeijer, Joachim; van Breukelen, B.M.; Ouboter, Maarten; Van Der Vlugt, Corné; Broers, Hans Peter

    2018-01-01

    The Amsterdam area, a highly manipulated delta area formed by polders and reclaimed lakes, struggles with high nutrient levels in its surface water system. The polders receive spatially and temporally variable amounts of water and nutrients via surface runoff, groundwater seepage, sewer leakage,

  9. Climate-Induced Thresholds In Lake-Watershed Systems: Understanding The Compounding Effects Of Early Ice-Out And Episodic Nutrient Loadings

    Science.gov (United States)

    Jain, S.; Beyene, M. T.

    2017-12-01

    In temperate regions, the sustainability of lake-watershed systems is intimately tied to the climate, ice phenology, annual march of human activities, and biophysical dynamics. Using the state of Maine in the United States as our focal region, one with over 5000 lakes. The recent rise in water temperatures, drop in water quality, depletion of fish stocks has raised concerns over the future state of these lakes. This study takes the "social-ecological systems" view of Maine lakes with focus on climate-induced shifts in the ice-cover duration. The resulting readjustments in the nutrient load assimilation, decrease in lake water quantity, increased radiative heating on phytoplankton productivity and economic and other losses to the community due to cancellation of winter recreation opportunities have the potential to reshape this vulnerable system. We use conceptual models, delineated social-ecological system, empirical-statistical analyses to grasp the complexity of this multifaceted system. Prospects for seasonal climate predictability and impact of the future trajectories of El Nino/Southern Oscillation are also discussed.

  10. An integrated modelling methodology to study the impacts of nutrients on coastal aquatic ecosystems in the context of climate change

    Science.gov (United States)

    Pesce, Marco; Critto, Andrea; Torresan, Silvia; Santini, Monia; Giubilato, Elisa; Pizzol, Lisa; Mercogliano, Paola; Zirino, Alberto; Wei, Ouyang; Marcomini, Antonio

    2017-04-01

    It has been recognized that the increase of atmospheric greenhouse gases (GHG) due to anthropogenic activities is causing changes in Earth's climate. Global mean temperatures are expected to rise by 0.3 to 4.8 °C by the end of the 21st century, and the water cycle to alter because of changes in global atmospheric moisture. Coastal waterbodies such as estuaries, bays and lagoons together with the ecological and socio-economic services they provide, could be among those most affected by the ongoing changes on climate. Because of their position at the land-sea interface, they are subjected to the combined changes in the physico-chemical processes of atmosphere, upstream land and coastal waters. Particularly, climate change is expected to alter phytoplankton communities by changing their climate and environmental drivers, such as temperature, precipitation, wind, solar radiation and nutrient loadings, and to exacerbate the symptoms of eutrophication events, such as hypoxia, harmful algal blooms (HAB) and loss of habitat. A better understanding of the links between climate-related drivers and phytoplankton is therefore necessary for predicting climate change impacts on aquatic ecosystems. In this context, the integration of climate scenarios and environmental models can become a valuable tool for the investigation and prediction of phytoplankton ecosystem dynamics under climate change conditions. In the last decade, the effects of climate change on the environmental distribution of nutrients and the resulting effects on aquatic ecosystems encouraged the conduction of modeling studies at a catchment scale, even though mainly are related to lake ecosystem. The further development of integrated modeling approaches and their application to other types of waterbodies such as coastal waters can be a useful contribution to increase the availability of management tools for ecological conservation and adaptation policies. Here we present the case study of the Zero river basin

  11. A Probabilistic Approach for Analysis of Modeling Uncertainties in Quantification of Trading Ratios in Nonpoint to Point Source Nutrient Trading Programs

    Science.gov (United States)

    Tasdighi, A.; Arabi, M.

    2015-12-01

    Quantifying the nonpoint source pollutant loads and assessing the water quality benefits of conservation practices (BMPs) are prone to different types of uncertainties which have to be taken into account when developing nutrient trading programs. Although various types of modeling uncertainties (parameter, input and structure) have been examined in the literature more or less, the impact of modeling uncertainties on evaluation of BMPs has not been addressed sufficiently. Currently, "trading ratios" are used within nutrient trading programs to account for variability of nonpoint source loads. However, we were not able to find any case of some rigorous scientific approach to account for any type of uncertainties in trading ratios. In this study, Bayesian inferences were applied to incorporate input, parameter and structural uncertainties using a statistically valid likelihood function. IPEAT (Integrated Parameter Estimation and Uncertainty Analysis Tool), a framework developed for simultaneous evaluation of parameterization, input data, model structure, and observation data uncertainty and their contribution to predictive uncertainty was used to quantify the uncertainties in effectiveness of agricultural BMPs while propagating different sources of uncertainty. SWAT was used as the simulation model. SWAT parameterization was done for three different model structures (SCS CN I, SCS CN II and G&A methods) using a Bayesian based Markov Chain Monte Carlo (MCMC) method named Differential Evolution Adaptive Metropolis (DREAM). For each model structure, the Integrated Bayesian Uncertainty Estimator (IBUNE) was employed to generate latent variables from input data. Bayesian Model Averaging (BMA) was then used to combine the models and Expectation-Maximization (EM) optimization technique was used to estimate the BMA weights. Using this framework, the impact of different sources of uncertainty on nutrient loads from nonpoint sources and subsequently effectiveness of BMPs in

  12. Dynamical Model of Rocket Propellant Loading with Liquid Hydrogen

    Data.gov (United States)

    National Aeronautics and Space Administration — A dynamical model describing the multi-stage process of rocket propellant loading has been developed. It accounts for both the nominal and faulty regimes of...

  13. Dynamic Regression Intervention Modeling for the Malaysian Daily Load

    Directory of Open Access Journals (Sweden)

    Fadhilah Abdrazak

    2014-05-01

    Full Text Available Malaysia is a unique country due to having both fixed and moving holidays.  These moving holidays may overlap with other fixed holidays and therefore, increase the complexity of the load forecasting activities. The errors due to holidays’ effects in the load forecasting are known to be higher than other factors.  If these effects can be estimated and removed, the behavior of the series could be better viewed.  Thus, the aim of this paper is to improve the forecasting errors by using a dynamic regression model with intervention analysis.   Based on the linear transfer function method, a daily load model consists of either peak or average is developed.  The developed model outperformed the seasonal ARIMA model in estimating the fixed and moving holidays’ effects and achieved a smaller Mean Absolute Percentage Error (MAPE in load forecast.

  14. A new theory of plant-microbe nutrient competition resolves inconsistencies between observations and model predictions.

    Science.gov (United States)

    Zhu, Qing; Riley, William J; Tang, Jinyun

    2017-04-01

    Terrestrial plants assimilate anthropogenic CO 2 through photosynthesis and synthesizing new tissues. However, sustaining these processes requires plants to compete with microbes for soil nutrients, which therefore calls for an appropriate understanding and modeling of nutrient competition mechanisms in Earth System Models (ESMs). Here, we survey existing plant-microbe competition theories and their implementations in ESMs. We found no consensus regarding the representation of nutrient competition and that observational and theoretical support for current implementations are weak. To reconcile this situation, we applied the Equilibrium Chemistry Approximation (ECA) theory to plant-microbe nitrogen competition in a detailed grassland 15 N tracer study and found that competition theories in current ESMs fail to capture observed patterns and the ECA prediction simplifies the complex nature of nutrient competition and quantitatively matches the 15 N observations. Since plant carbon dynamics are strongly modulated by soil nutrient acquisition, we conclude that (1) predicted nutrient limitation effects on terrestrial carbon accumulation by existing ESMs may be biased and (2) our ECA-based approach may improve predictions by mechanistically representing plant-microbe nutrient competition. © 2016 by the Ecological Society of America.

  15. A model for voltage collapse study considering load characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Aguiar, L.B. [Companhia de Energia Eletrica da Bahia (COELBA), Salvador, BA (Brazil)

    1994-12-31

    This paper presents a model for analysis of voltage collapse and instability problem considering the load characteristics. The model considers fundamentally the transmission lines represented by exact from through the generalized constants A, B, C, D and the loads as function of the voltage, emphasizing the cases of constant power, constant current and constant impedance. the study treats of the system behavior on steady state and presents illustrative graphics about the problem. (author) 12 refs., 4 figs.

  16. Fire Response of Loaded Composite Structures - Experiments and Modeling

    OpenAIRE

    Burdette, Jason A.

    2001-01-01

    In this work, the thermo-mechanical response and failure of loaded, fire-exposed composite structures was studied. Unique experimental equipment and procedures were developed and experiments were performed to assess the effects of mechanical loading and fire exposure on the service life of composite beams. A series of analytical models was assembled to describe the fire growth and structural response processes for the system used in the experiments. This series of models consists of a fire...

  17. Glutamate prevents intestinal atrophy via luminal nutrient sensing in a mouse model of total parenteral nutrition

    DEFF Research Database (Denmark)

    Xiao, Weidong; Feng, Yongjia; Holst, Jens Juul

    2014-01-01

    Small intestine luminal nutrient sensing may be crucial for modulating physiological functions. However, its mechanism of action is incompletely understood. We used a model of enteral nutrient deprivation, or total parenteral nutrition (TPN), resulting in intestinal mucosal atrophy and decreased...... was regulated by T1R3 and mGluR5, suggesting a novel negative regulator pathway for IEC proliferation not previously described. Loss of luminal nutrients with TPN administration may widely affect intestinal taste sensing. GLM has previously unrecognized actions on IEC growth and EBF. Restoring luminal sensing...

  18. Environmental impact of aquaculture-sedimentation and nutrient loadings from shrimp culture of the southeast coastal region of the Bay of Bengal.

    Science.gov (United States)

    Das, Biplob; Khan, Yusuf Sharif Ahmed; Das, Pranab

    2004-01-01

    Nutrient loadings were measured for surface seawater and bottom sediments of semi-intensive and improved extensive shrimp culture pond, adjacent estuary, and fallow land in the south-east coastal region of Bangladesh during August, 2000-January, 2001 to evaluate the impact of shrimp culture. The mean levels of nutrients found in the pond surface water were 108.780 mg/L for CaCO3, 0.526 mg/L for NH4+ -N, 3.075 wt% for organic carbon, 7.00 mg/L for PO4-P, 5.57 mg/L for NO3-N, and 7.33 mg/L for chlorophyll-a. The maximum mean value of H2S (0.232 mg/L) was found in estuarine water. Nutrients loading were found to be decreased with distance from the shrimp farm discharge unit in estuarine water. The mean level of organic matter, total nitrogen, and organic carbon were found in higher concentrations in sediments of cultured pond compared to bottom soil of adjacent fallow land at the same elevation. Extractable Ca values were found in higher concentration (550.33 ppt) in adjacent fallow land, as the shrimps for molting in shrimp ponds use extractable Ca. The relation between seawater H2S value and sediment pH (r = - 0.94); sediment organic carbon and sediment pH values (r = -0.76), sediment total nitrogen and sediment pH (r = -0.74) were found to be highly negatively correlated. Whereas the relation between seawater H2S value and sediment total nitrogen (r = 0.92), water NH4+ -N and sediment pH (r = 0.66) were found to be positively correlated. The results revealed that load of nutrients at eutrophic level in estuarine water, and decrease of soil pH; leading to acid sulphate soil formation indicates a negative impact of shrimp culture.

  19. Fine bakery wares with label claims in Europe and their categorisation by nutrient profiling models.

    Science.gov (United States)

    Trichterborn, J; Harzer, G; Kunz, C

    2011-03-01

    This study assesses a range of commercially available fine bakery wares with nutrition or health related on-pack communication against the criteria of selected nutrient profiling models. Different purposes of the application of nutrient profiles were considered, including front-of-pack signposting and the regulation of claims or advertising. More than 200 commercially available fine bakery wares carrying claims were identified in Germany, France, Spain, Sweden and United Kingdom and evaluated against five nutrient profiling models. All models were assessed regarding their underlying principles, generated results and inter-model agreement levels. Total energy, saturated fatty acids, sugars, sodium and fibre were critical parameters for the categorisation of products. The Choices Programme was the most restrictive model in this category, while the Food and Drug Administration model allowed the highest number of products to qualify. According to all models, more savoury than sweet products met the criteria. On average, qualifying products contained less than half the amounts of nutrients to limit and more than double the amount of fibre compared with all the products in the study. None of the models had a significant impact on the average energy contents. Nutrient profiles can be applied to identify fine bakery wares with a significantly better nutritional composition than the average range of products positioned as healthier. Important parameters to take into account include energy, saturated fatty acids, sugars, sodium and fibre. Different criteria sets for subcategories of fine bakery wares do not seem necessary.

  20. Testing and modeling of cyclically loaded rock anchors

    Directory of Open Access Journals (Sweden)

    Joar Tistel

    2017-12-01

    Full Text Available The Norwegian Public Roads Administration (NPRA is planning for an upgrade of the E39 highway route at the westcoast of Norway. Fixed links shall replace ferries at seven fjord crossings. Wide spans and large depths at the crossings combined with challenging subsea topography and environmental loads call for an extension of existing practice. A variety of bridge concepts are evaluated in the feasibility study. The structures will experience significant loads from deadweight, traffic and environment. Anchoring of these forces is thus one of the challenges met in the project. Large-size subsea rock anchors are considered a viable alternative. These can be used for anchoring of floating structures but also with the purpose of increasing capacity of fixed structures. This paper presents first a thorough study of factors affecting rock anchor bond capacity. Laboratory testing of rock anchors subjected to cyclic loading is thereafter presented. Finally, the paper presents a model predicting the capacity of a rock anchor segment, in terms of a ribbed bar, subjected to a cyclic load history. The research assumes a failure mode occurring in the interface between the rock anchor and the surrounding grout. The constitutive behavior of the bonding interface is investigated for anchors subjected to cyclic one-way tensile loads. The model utilizes the static bond capacity curve as a basis, defining the ultimate bond τbu and the slip s1 at τbu. A limited number of input parameters are required to apply the model. The model defines the bond-slip behavior with the belonging rock anchor capacity depending on the cyclic load level (τmax cy/τbu, the cyclic load ratio (R = τmin cy/τmax cy, and the number of load cycles (N. The constitutive model is intended to model short anchor lengths representing an incremental length of a complete rock anchor.

  1. Aggregation model for curtailable generation and sheddable loads

    DEFF Research Database (Denmark)

    Marthinsen, Håkon; Morch, Andrei Z.; Plećaš, Milana

    2017-01-01

    This study shows modelling developed during the first year of the SmartNet project. In particular, it presents a mathematical model for aggregation of curtailable generation and sheddable loads. The model determines the quantity and the cost of the flexibility provided by the flexible resources...

  2. Nutrient, organic carbon, and chloride concentrations and loads in selected Long Island Sound tributaries—Four decades of change following the passage of the Federal Clean Water Act

    Science.gov (United States)

    Mullaney, John R.

    2016-03-10

    Trends in long-term water-quality and streamflow data from 14 water-quality monitoring sites in Connecticut were evaluated for water years 1974–2013 and 2001–13, coinciding with implementation of the Clean Water Act of 1972 and the Connecticut Nitrogen Credit Exchange program, as part of an assessment of nutrient and chloride concentrations and loads discharged to Long Island Sound. In this study, conducted by the U.S. Geological Survey in cooperation with the Connecticut Department of Energy and Environmental Protection, data were evaluated using a recently developed methodology of weighted regressions with time, streamflow, and season. Trends in streamflow were evaluated using a locally weighted scatterplot smoothing method. Annual mean streamflow increased at 12 of the 14 sites averaging 8 percent during the entire study period, primarily in the summer months, and increased by an average of 9 percent in water years 2001–13, primarily during summer and fall months. Downward trends in flow-normalized nutrient concentrations and loads were observed during both periods for most sites for total nitrogen, total Kjeldahl nitrogen, nitrite plus nitrate nitrogen, total phosphorus, and total organic carbon. Average flow-normalized loads of total nitrogen decreased by 23.9 percent for the entire period and 10.9 percent for the period of water years 2001‒13. Major factors contributing to decreases in flow-normalized loads and concentrations of these nutrients include improvements in wastewater treatment practices, declining atmospheric wet deposition of nitrogen, and changes in land management and land use.

  3. Mathematical human body modelling for impact loading

    NARCIS (Netherlands)

    Happee, R.; Morsink, P.L.J.; Wismans, J.S.H.M.

    1999-01-01

    Mathematical modelling of the human body is widely used for automotive crash safety research and design. Simulations have contributed to a reduction of injury numbers by optimisation of vehicle structures and restraint systems. Currently such simulations are largely performed using occupant models

  4. Data Used in Analyses of Trends, and Nutrient and Suspended-Sediment Loads for Streams in the Southeastern United States, 1973-2005

    Science.gov (United States)

    Staub, Erik L.; Peak, Kelly L.; Tighe, Kirsten C.; Sadorf, Eric M.; Harned, Douglas A.

    2010-01-01

    Water-quality data from selected surface-water monitoring sites in the Southeastern United States were assessed for trends in concentrations of nutrients, suspended sediment, and major constituents and for in-stream nutrient and suspended-sediment loads for the period 1973-2005. The area of interest includes river basins draining into the southern Atlantic Ocean, the Gulf of Mexico, and the Tennessee River-drainage basins in Hydrologic Regions 03 (South Atlantic - Gulf) and 06 (Tennessee). This data assessment is related to studies of several major river basins as part of the U.S. Geological Survey National Water-Quality Assessment Program, which was designed to assess national water-quality trends during a common time period (1993-2004). Included in this report are data on which trend tests could be performed from 44 U.S. Geological Survey National Water Information System (NWIS) sampling sites. The constituents examined include major ions, nutrients, and suspended sediment; the physical properties examined include pH, specific conductance, dissolved oxygen, and streamflow. Also included are data that were tested for trends from an additional 290 sites from the U.S. Environmental Protection Agency Storage and Retrieval (STORET) database. The trend analyses of the STORET data were limited to total nitrogen and total phosphorus concentrations. Data from 48 U.S. Geological Survey NWIS sampling sites with sufficient water-quality and continuous streamflow data for estimating nutrient and sediment loads are included. The methods of data compilation and modification used prior to performing trend tests and load estimation are described. Results of the seasonal Kendall trend test and the Tobit trend test are given for the 334 monitoring sites, and in-stream load estimates are given for the 48 monitoring sites. Basin characteristics are provided, including regional landscape variables and agricultural nutrient sources (annual variations in cropping and fertilizer use

  5. Study on Standard Fatigue Vehicle Load Model

    Science.gov (United States)

    Huang, H. Y.; Zhang, J. P.; Li, Y. H.

    2018-02-01

    Based on the measured data of truck from three artery expressways in Guangdong Province, the statistical analysis of truck weight was conducted according to axle number. The standard fatigue vehicle model applied to industrial areas in the middle and late was obtained, which adopted equivalence damage principle, Miner linear accumulation law, water discharge method and damage ratio theory. Compared with the fatigue vehicle model Specified by the current bridge design code, the proposed model has better applicability. It is of certain reference value for the fatigue design of bridge in China.

  6. Evaluation and management of the impact of land use change on the nitrogen and phosphorus load delivered to surface waters: the export coefficient modelling approach

    Science.gov (United States)

    Johnes, P. J.

    1996-09-01

    A manageable, relatively inexpensive model was constructed to predict the loss of nitrogen and phosphorus from a complex catchment to its drainage system. The model used an export coefficient approach, calculating the total nitrogen (N) and total phosphorus (P) load delivered annually to a water body as the sum of the individual loads exported from each nutrient source in its catchment. The export coefficient modelling approach permits scaling up from plot-scale experiments to the catchment scale, allowing application of findings from field experimental studies at a suitable scale for catchment management. The catchment of the River Windrush, a tributary of the River Thames, UK, was selected as the initial study site. The Windrush model predicted nitrogen and phosphorus loading within 2% of observed total nitrogen load and 0.5% of observed total phosphorus load in 1989. The export coefficient modelling approach was then validated by application in a second research basin, the catchment of Slapton Ley, south Devon, which has markedly different catchment hydrology and land use. The Slapton model was calibrated within 2% of observed total nitrogen load and 2.5% of observed total phosphorus load in 1986. Both models proved sensitive to the impact of temporal changes in land use and management on water quality in both catchments, and were therefore used to evaluate the potential impact of proposed pollution control strategies on the nutrient loading delivered to the River Windrush and Slapton Ley.

  7. Hydrological improvements for nutrient and pollutant emission modeling in large scale catchments

    Science.gov (United States)

    Höllering, S.; Ihringer, J.

    2012-04-01

    An estimation of emissions and loads of nutrients and pollutants into European water bodies with as much accuracy as possible depends largely on the knowledge about the spatially and temporally distributed hydrological runoff patterns. An improved hydrological water balance model for the pollutant emission model MoRE (Modeling of Regionalized Emissions) (IWG, 2011) has been introduced, that can form an adequate basis to simulate discharge in a hydrologically differentiated, land-use based way to subsequently provide the required distributed discharge components. First of all the hydrological model had to comply both with requirements of space and time in order to calculate sufficiently precise the water balance on the catchment scale spatially distributed in sub-catchments and with a higher temporal resolution. Aiming to reproduce seasonal dynamics and the characteristic hydrological regimes of river catchments a daily (instead of a yearly) time increment was applied allowing for a more process oriented simulation of discharge dynamics, volume and therefore water balance. The enhancement of the hydrological model became also necessary to potentially account for the hydrological functioning of catchments in regard to scenarios of e.g. a changing climate or alterations of land use. As a deterministic, partly physically based, conceptual hydrological watershed and water balance model the Precipitation Runoff Modeling System (PRMS) (USGS, 2009) was selected to improve the hydrological input for MoRE. In PRMS the spatial discretization is implemented with sub-catchments and so called hydrologic response units (HRUs) which are the hydrotropic, distributed, finite modeling entities each having a homogeneous runoff reaction due to hydro-meteorological events. Spatial structures and heterogeneities in sub-catchments e.g. urbanity, land use and soil types were identified to derive hydrological similarities and classify in different urban and rural HRUs. In this way the

  8. Assessing winter cover crop nutrient uptake efficiency using a water quality simulation model

    Science.gov (United States)

    Yeo, In-Young; Lee, Sangchui; Sadeghi, Ali M.; Beeson, Peter C.; Hively, W. Dean; McCarty, Greg W.; Lang, Megan W.

    2013-01-01

    Winter cover crops are an effective conservation management practice with potential to improve water quality. Throughout the Chesapeake Bay Watershed (CBW), which is located in the Mid-Atlantic US, winter cover crop use has been emphasized and federal and state cost-share programs are available to farmers to subsidize the cost of winter cover crop establishment. The objective of this study was to assess the long-term effect of planting winter cover crops at the watershed scale and to identify critical source areas of high nitrate export. A physically-based watershed simulation model, Soil and Water Assessment Tool (SWAT), was calibrated and validated using water quality monitoring data and satellite-based estimates of winter cover crop species performance to simulate hydrological processes and nutrient cycling over the period of 1991–2000. Multiple scenarios were developed to obtain baseline information on nitrate loading without winter cover crops planted and to investigate how nitrate loading could change with different winter cover crop planting scenarios, including different species, planting times, and implementation areas. The results indicate that winter cover crops had a negligible impact on water budget, but significantly reduced nitrate leaching to groundwater and delivery to the waterways. Without winter cover crops, annual nitrate loading was approximately 14 kg ha−1, but it decreased to 4.6–10.1 kg ha−1 with winter cover crops resulting in a reduction rate of 27–67% at the watershed scale. Rye was most effective, with a potential to reduce nitrate leaching by up to 93% with early planting at the field scale. Early planting of winter cover crops (~30 days of additional growing days) was crucial, as it lowered nitrate export by an additional ~2 kg ha−1 when compared to late planting scenarios. The effectiveness of cover cropping increased with increasing extent of winter cover crop implementation. Agricultural fields with well-drained soils

  9. Energy and nutrient deposition and excretion in the reproducing sow: model development and evaluation

    DEFF Research Database (Denmark)

    Hansen, A V; Strathe, A B; Theil, Peter Kappel

    2014-01-01

    was related to predictions of body fat and protein loss from the lactation model. Nitrogen intake, urine N, fecal N, and milk N were predicted with RMSPE as percentage of observed mean of 9.7, 17.9, 10.0, and 7.7%, respectively. The model provided a framework, but more refinements and improvements in accuracy......Air and nutrient emissions from swine operations raise environmental concerns. During the reproduction phase, sows consume and excrete large quantities of nutrients. The objective of this study was to develop a mathematical model to describe energy and nutrient partitioning and predict manure...... excretion and composition and methane emissions on a daily basis. The model was structured to contain gestation and lactation modules, which can be run separately or sequentially, with outputs from the gestation module used as inputs to the lactation module. In the gestating module, energy and protein...

  10. Global dynamics in a stoichiometric food chain model with two limiting nutrients.

    Science.gov (United States)

    Chen, Ming; Fan, Meng; Kuang, Yang

    2017-07-01

    Ecological stoichiometry studies the balance of energy and multiple chemical elements in ecological interactions to establish how the nutrient content affect food-web dynamics and nutrient cycling in ecosystems. In this study, we formulate a food chain with two limiting nutrients in the form of a stoichiometric population model. A comprehensive global analysis of the rich dynamics of the targeted model is explored both analytically and numerically. Chaotic dynamic is observed in this simple stoichiometric food chain model and is compared with traditional model without stoichiometry. The detailed comparison reveals that stoichiometry can reduce the parameter space for chaotic dynamics. Our findings also show that decreasing producer production efficiency may have only a small effect on the consumer growth but a more profound impact on the top predator growth. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. Neural correlates of internal-model loading.

    Science.gov (United States)

    Bursztyn, Lulu L C D; Ganesh, G; Imamizu, Hiroshi; Kawato, Mitsuo; Flanagan, J Randall

    2006-12-19

    Skilled object manipulation requires knowledge, or internal models, of object dynamics relating applied force to motion , and our ability to handle myriad objects indicates that the brain maintains multiple models . Recent behavioral studies have shown that once learned, an internal model of an object with novel dynamics can be rapidly recruited and derecruited as the object is grasped and released . We used event-related fMRI to investigate neural activity linked to grasping an object with recently learned dynamics in preparation for moving it after a delay. Subjects also performed two control tasks in which they either moved without the object in hand or applied isometric forces to the object. In all trials, subjects received a cue indicating which task to perform in response to a go signal delivered 5-10 s later. We examined BOLD responses during the interval between the cue and go and assessed the conjunction of the two contrasts formed by comparing the primary task to each control. The analysis revealed significant activity in the ipsilateral cerebellum and the contralateral and supplementary motor areas. We propose that these regions are involved in internal-model recruitment in preparation for movement execution.

  12. Dominance patterns in macroalgal and phytoplankton biomass under different nutrient loads in subtropical coastal lagoons of the SE Gulf of California.

    Science.gov (United States)

    Páez-Osuna, F; Piñón-Gimate, A; Ochoa-Izaguirre, M J; Ruiz-Fernández, A C; Ramírez-Reséndiz, G; Alonso-Rodríguez, R

    2013-12-15

    Nine macroalgal blooms were studied in five coastal lagoons of the SE Gulf of California. The nutrient loads from point and diffuse sources were estimated in the proximity of the macroalgal blooms. Chlorophyll a and macroalgal biomass were measured during the dry, rainy and cold seasons. Shrimp farms were the main point source of nitrogen and phosphorus loads for the lagoons. High biomasses were found during the dry season for phytoplankton at site 6 (791.7±34.6 mg m(-2)) and during the rainy season for macroalgae at site 4 (296.0±82.4 g m(-2)). Depending on the season, the phytoplankton biomass ranged between 40.0 and 791.7 mg m(-2) and the macroalgal biomass between 1 and 296.0 g m(-2). The bulk biomass (phytoplankton+macroalgal) displayed the same tendency as the nutrient loads entering the coastal lagoons. Phytoplankton and macroalgal biomass presented a significant correlation with the atomic N:P ratio. Copyright © 2013 Elsevier Ltd. All rights reserved.

  13. Nutrient and metal loads estimated by using discrete, automated, and continuous water-quality monitoring techniques for the Blackstone River at the Massachusetts-Rhode Island State line, water years 2013–14

    Science.gov (United States)

    Sorenson, Jason R.; Granato, Gregory E.; Smith, Kirk P.

    2018-01-10

    Flow-proportional composite water samples were collected in water years 2013 and 2014 by the U.S. Geological Survey, in cooperation with the Massachusetts Department of Environmental Protection, from the Blackstone River at Millville, Massachusetts (U.S. Geological Survey station 01111230), about 0.5 mile from the border with Rhode Island. Samples were collected in order to better understand the dynamics of selected nutrient and metal constituents, assist with planning, guide activities to meet water-quality goals, and provide real-time water-quality information to the public. An automated system collected the samples at 14-day intervals to determine total and dissolved nitrogen and phosphorus concentrations, to provide accurate monthly nutrient concentration data, and to calculate monthly load estimates. Concentrations of dissolved trace metals and total aluminum were determined from 4-day composite water samples that were collected twice monthly by the automated system. Results from 4-day composites provide stakeholders with information to evaluate trace metals on the basis of chronic 4-day exposure criteria for aquatic life, and the potential to use the biotic ligand model to evaluate copper concentrations. Nutrient, trace metal, suspended sediment, dissolved organic carbon, and chlorophyll a concentrations were determined from discrete samples collected at the Millville station and from across the stream transect at the upstream railroad bridge, and these concentrations served as a means to evaluate the representativeness of the Millville point location.Analytical results from samples collected with the automated flow-proportional sampling system provided the means to calculate monthly and annual loading data. Total nitrogen and total phosphorus loads in water year (WY) 2013 were about 447,000 and 36,000 kilograms (kg), respectively. In WY 2014, annual loads of total nitrogen and total phosphorus were about 342,000 and 21,000 kg, respectively. Total nitrogen

  14. Field Scale Groundwater Nitrate Loading Model for the Central Valley, California, 1945-Current

    Science.gov (United States)

    Harter, T.; Dzurella, K.; Bell, A.; Kourakos, G.

    2015-12-01

    Anthropogenic groundwater nitrate contamination in the Central Valley aquifer system, California, is widespread, with over 40% of domestic wells in some counties exceeding drinking water standards. Sources of groundwater nitrate include leaky municipal wastewater systems, municipal wastewater recharge, onsite wastewater treatment (septic) systems, atmospheric nitrogen deposition, animal farming, application of organic waste materials (sludge, biosolids, animal manure) to agricultural lands, and synthetic fertilizer. At the site or field scale, nitrogen inputs to the landscape are balanced by plant nitrogen uptake and harvest, atmospheric nitrogen losses, surface runoff of nitrogen, soil nitrogen storage changes, and leaching to groundwater. Irrigated agriculture is a dominant player in the Central Valley nitrogen cycle: The largest nitrogen fluxes are synthetic fertilizer and animal manure applications to cropland, crop nitrogen uptake, and groundwater nitrogen losses. We construct a historic field/parcel scale groundwater nitrogen loading model distinguishing urban and residential areas, individual animal farming areas, leaky wastewater lagoons, and approximately 50 different categories of agricultural crops. For non-agricultural landuses, groundwater nitrate loading is based on reported leaching values, animal population, and human population. For cropland, groundwater nitrate loading is computed from mass balance, taking into account diverse and historically changing management practices between different crops. Groundwater nitrate loading is estimated for 1945 to current. Significant increases in groundwater nitrate loading are associated with the expansion of synthetic fertilizer use in the 1950s to 1970s. Nitrate loading from synthetic fertilizer use has stagnated over the past 20 years due to improvements in nutrient use efficiency. However, an unbroken 60 year exponential increase in dairy production until the late 2000s has significantly impacted the

  15. Assessing the influence of nutrient reduction on water quality using a three-dimensional model: case study in a tidal estuarine system.

    Science.gov (United States)

    Liu, Wen-Cheng; Chan, Wen-Ting

    2014-12-01

    A coupled three-dimensional hydrodynamic and water quality model has been developed and applied to the Danshuei River estuarine system and adjacent coastal sea. The water quality model considers various species of nitrogen, phosphorus, organic carbon, and phytoplankton as well as dissolved oxygen and is driven by a three-dimensional hydrodynamic model. The hydrodynamic and water quality models were validated with observations of water surface elevation, velocity, salinity distribution, and water quality parameters. Statistical error analysis shows that predictions of hydrodynamics, salinity, dissolved oxygen, and nutrients from the model simulation quantitatively agreed with the observed data. The validated model was then applied to predict water quality conditions as a result of a reduction in nutrient loadings based on different engineering strategies. The simulated results revealed that the dissolved oxygen concentration would increase significantly and would be higher than 2 mg/L in the main stream and in three tributaries to meet the minimum statutory requirement for dissolved oxygen. Active estuarine management focused on the reduction of anthropogenic nutrient loads is needed for improvement in water quality.

  16. Contribution of riverine nutrients to the silicon biogeochemistry of the global ocean – a model study

    Directory of Open Access Journals (Sweden)

    C. Y. Bernard

    2011-03-01

    Full Text Available Continental shelf seas are known to support a large fraction of the global primary production. Yet, they are mostly ignored or neglected in global biogeochemical models. A number of processes that control the transfer of dissolved nutrients from rivers to the open ocean remain poorly understood. This applies in particular to dissolved silica which drives the growth of diatoms that form a large part of the phytoplankton biomass and are thus an important contributor to export production of carbon.

    Here, the representation of the biogeochemical cycling along continents is improved by coupling a high resolution database of riverine fluxes of nutrients to the global biogeochemical ocean general circulation model HAMOCC5-OM. Focusing on silicon (Si, but including the whole suite of nutrients – carbon (C, nitrogen (N and phosphorus (P in various forms – inputs are implemented in the model at coastal coupling points using the COSCAT global database of 156 mega-river-ensemble catchments from Meybeck et al. (2006. The catchments connect to the ocean through coastal segments according to three sets of criteria: natural limits, continental shelf topography, and geophysical dynamics.

    According to the model the largest effects on nutrient concentrations occur in hot spots such as the Amazon plume, the Arctic – with high nutrient inputs in relation to its total volume, and areas that encounter the largest increase in human activity, e.g., Southern Asia.

  17. Modeling Escherichia coli removal in constructed wetlands under pulse loading.

    Science.gov (United States)

    Hamaamin, Yaseen A; Adhikari, Umesh; Nejadhashemi, A Pouyan; Harrigan, Timothy; Reinhold, Dawn M

    2014-03-01

    Manure-borne pathogens are a threat to water quality and have resulted in disease outbreaks globally. Land application of livestock manure to croplands may result in pathogen transport through surface runoff and tile drains, eventually entering water bodies such as rivers and wetlands. The goal of this study was to develop a robust model for estimating the pathogen removal in surface flow wetlands under pulse loading conditions. A new modeling approach was used to describe Escherichia coli removal in pulse-loaded constructed wetlands using adaptive neuro-fuzzy inference systems (ANFIS). Several ANFIS models were developed and validated using experimental data under pulse loading over two seasons (winter and summer). In addition to ANFIS, a mechanistic fecal coliform removal model was validated using the same sets of experimental data. The results showed that the ANFIS model significantly improved the ability to describe the dynamics of E. coli removal under pulse loading. The mechanistic model performed poorly as demonstrated by lower coefficient of determination and higher root mean squared error compared to the ANFIS models. The E. coli concentrations corresponding to the inflection points on the tracer study were keys to improving the predictability of the E. coli removal model. Copyright © 2013 Elsevier Ltd. All rights reserved.

  18. Different Effects of Corn Ethanol and Switchgrass-Based Biofuels on Soil Erosion and Nutrients Loads in the Iowa River Basin

    Science.gov (United States)

    Wu, Y.; Liu, S.

    2010-12-01

    Biofuels have become important alternative energy resources and their use is likely to expand in the foreseeable future. The expansion of corn-based ethanol production has resulted in a tightening of the global corn supply-and-demand balance. Perennial grasses such as switchgrass (Panicum virgatum) are also being considered as candidates for biofuel feedstocks. Expansion of biofuel production will generate diverse impacts on the economy and environment. How to optimize land use activities to address the need for biofuel production while protecting the environment is still a grand challenge. Unfortunately, little is known about the effects of biofuel-oriented alternative land uses on water quality. Can we produce the same amount or more biofuels by converting some cornfields to switchgrass, for example, while reducing environmental pressure? The objective of this study was to evaluate the potential impacts of land cover change from corn to switchgrass (e.g., on marginal lands) and related management activities on water quality in the Iowa River Basin (drainage area of 32,360 km2) using the Soil and Water Assessment Tool (SWAT). The model was calibrated and validated under baseline conditions using daily streamflow and sediment, and monthly nutrients at Wapello, Iowa (near the outlet of the watershed). The preliminary results show that both the annual average sediment yield and nitrate nitrogen load would decrease when marginal corn areas are converted to switchgrass. However, the magnitude of change depends greatly on the detailed management practices, such as techniques and amount of fertilization, harvesting practices, and residue management.

  19. Changes in distributional patterns of plaice Pleuronectes platessa in the central and eastern North Sea; do declining nutrient loadings play a role?

    DEFF Research Database (Denmark)

    Støttrup, Josianne Gatt; Munk, Peter; Kodama, Masashi

    2017-01-01

    Since the beginning of the 1990s, there has been a change in the relative distribution of smaller age-classes of plaice Pleuronectes platessa (age 1–3) in the North Sea. The abundances have increased in deeper, more offshore areas, while coastal abundances have been stagnant or declining. For the...... from conditions specific for near-shore areas, such as nutrient loadings in coastal waters and export offshore. The concurrent changes in environment and in distribution of juvenile plaice may have implications for environmental and fisheries management...

  20. Modelling of a chaotic load of wind turbines drivetrain

    Science.gov (United States)

    Bielecki, Andrzej; Barszcz, Tomasz; Wójcik, Mateusz

    2015-03-01

    The purpose of this paper is to present a model of the load of the wind turbine gears for simulation of real, varying operational conditions for modelling of wind turbine vibration. The characteristics of the wind, which generates chaotically varying loads on the drivetrain components generating load in teeth and bearings of gears during torque transfer, are discussed. A generator of variable load of wind turbines drivetrain is proposed. Firstly, the module for generation of wind speed is designed. It is based on the approach in which the wind speed was considered as a time series approximated by the Weierstrass function. Secondly, the rotational speed of the main shaft is proposed as a function of the wind speed value. The function depends on a few parameters that are fitted by using a genetic algorithm. Finally, the model of torque of the main shaft is introduced. This model has been created by using a multi-layer artificial neural network. The results show that the proposed approach yields a very good fit for the experimental data. The fit brings about the proper reproducing of all the aspects of the load that are crucial for causing fatigue and, as a consequence, damaging of gears of the wind turbines.

  1. Concentrations and loads of nutrients in the tributaries of the Lake Okeechobee watershed, south-central Florida, water years 2004-2008

    Science.gov (United States)

    Byrne, Michael J.; Wood, Molly S.

    2011-01-01

    Lake Okeechobee in south-central Florida is the second largest freshwater lake in the contiguous United States. Excessive phosphorus loading, harmful high and low water levels, and rapid expansion of non-native vegetation have threatened the health of the lake in recent decades. A study was conducted to monitor discharge and nutrient concentrations from selected tributaries into Lake Okeechobee and to evaluate nutrient loads. The data analysis was performed at 16 monitoring stations from December 2003 to September 2008. Annual and seasonal discharge measured at monitoring stations is affected by rainfall. Hurricanes affected three wet years (2004, 2005, and the latter part of 2008) and resulted in substantially greater discharge than the drought years of 2006, 2007, and the early part of 2008. Rainfall supplies about 50 percent of the water to Lake Okeechobee, discharge from the Kissimmee River supplies about 25 percent, and discharge from tributaries and groundwater seepage along the lake perimeter collectively provide the remaining 25 percent. Annually, tributary discharge from basins located on the west side of the Kissimmee River is about 5 to 6 times greater than that from basins located on the east side. For the purposes of this study, the basins on the east side of the Kissimmee River are called "priority basins" because of elevated phosphorus concentrations, while those on the west side are called "nonpriority" basins. Total annual discharge in the non-priority basins ranged from 245,000 acre-feet (acre-ft) in 2007 to 1,322,000 acre-ft in 2005, while annual discharge from the priority basins ranged from 41,000 acre-ft in 2007 to 219,000 acre-ft in 2005. Mean total phosphorus concentrations ranged from 0.10 to 0.54 milligrams per liter (mg/L) at the 16 tributaries during 2004–2008. Mean concentrations were significantly higher at priority basin sites than at non-priority basin sites, particularly at Arbuckle Creek and C 41A Canal. Concentrations of organic

  2. A computational model of blast loading on the human eye.

    Science.gov (United States)

    Bhardwaj, Rajneesh; Ziegler, Kimberly; Seo, Jung Hee; Ramesh, K T; Nguyen, Thao D

    2014-01-01

    Ocular injuries from blast have increased in recent wars, but the injury mechanism associated with the primary blast wave is unknown. We employ a three-dimensional fluid-structure interaction computational model to understand the stresses and deformations incurred by the globe due to blast overpressure. Our numerical results demonstrate that the blast wave reflections off the facial features around the eye increase the pressure loading on and around the eye. The blast wave produces asymmetric loading on the eye, which causes globe distortion. The deformation response of the globe under blast loading was evaluated, and regions of high stresses and strains inside the globe were identified. Our numerical results show that the blast loading results in globe distortion and large deviatoric stresses in the sclera. These large deviatoric stresses may be indicator for the risk of interfacial failure between the tissues of the sclera and the orbit.

  3. Modelling the Load Torques of Electric Drive for Polymerization Process

    Directory of Open Access Journals (Sweden)

    Andrzej Popenda

    2007-01-01

    Full Text Available The problems of mathematical modelling the load torques on shaft of driving motor designed for applications in polymerization reactors are presented in the paper. The real load of polymerization drive is determined as a function of angular velocity. Mentioned function results from friction in roll-formed slide bearing as well as from friction of ethylene molecules with mixer arms in polymerization reactor chamber. Application of mathematical formulas concerning the centrifugal ventilator is proposed to describe the mixer in reactor chamber. The analytical formulas describing the real loads of polymerization drive are applied in mathematical modelling the power unit of polymerization reactor with specially designed induction motor. The numerical analysis of transient states was made on the basis of formulated mathematical model. Examples of transient responses and trajectories resulting from analysis are presented in the paper.

  4. Nutrient additions in pristine Patagonian Sphagnum bog vegetation : can phosphorus addition alleviate (the effects of) increased nitrogen loads

    NARCIS (Netherlands)

    Fritz, C.; Dijk, G. van; Smolders, A.J.P.; Pancotto, V.A.; Elzenga, J.T.M.; Roelofs, J.G.M.; Grootjans, A.P.

    Sphagnum-bog ecosystems have a limited capability to retain carbon and nutrients when subjected to increased nitrogen (N) deposition. Although it has been proposed that phosphorus (P) can dilute negative effects of nitrogen by increasing biomass production of Sphagnum mosses, it is still unclear

  5. Waves and high nutrient loads jointly decrease survival and separately affect morphological and biomechanical properties in the seagrass

    NARCIS (Netherlands)

    La Nafie, Y.A.; de los Santos, C.B.; Brun, F.G.; van Katwijk, M.M.; Bouma, T.J.

    2012-01-01

    In an 8-week aquarium experiment, we investigated the interactive effects of waves (present vs. absent) and water-column nutrient level (high vs. low) on the survival, growth, morphology, and biomechanics of the seagrass, Zostera noltii. Survival was reduced when plants were exposed to both waves

  6. A Simple Hybrid Model for Short-Term Load Forecasting

    Directory of Open Access Journals (Sweden)

    Suseelatha Annamareddi

    2013-01-01

    Full Text Available The paper proposes a simple hybrid model to forecast the electrical load data based on the wavelet transform technique and double exponential smoothing. The historical noisy load series data is decomposed into deterministic and fluctuation components using suitable wavelet coefficient thresholds and wavelet reconstruction method. The variation characteristics of the resulting series are analyzed to arrive at reasonable thresholds that yield good denoising results. The constitutive series are then forecasted using appropriate exponential adaptive smoothing models. A case study performed on California energy market data demonstrates that the proposed method can offer high forecasting precision for very short-term forecasts, considering a time horizon of two weeks.

  7. Modeling vertical loads in pools resulting from fluid injection. [BWR

    Energy Technology Data Exchange (ETDEWEB)

    Lai, W.; McCauley, E.W.

    1978-06-15

    Table-top model experiments were performed to investigate pressure suppression pool dynamics effects due to a postulated loss-of-coolant accident (LOCA) for the Peachbottom Mark I boiling water reactor containment system. The results guided subsequent conduct of experiments in the /sup 1///sub 5/-scale facility and provided new insight into the vertical load function (VLF). Model experiments show an oscillatory VLF with the download typically double-spiked followed by a more gradual sinusoidal upload. The load function contains a high frequency oscillation superimposed on a low frequency one; evidence from measurements indicates that the oscillations are initiated by fluid dynamics phenomena.

  8. Modeling vertical loads in pools resulting from fluid injection

    International Nuclear Information System (INIS)

    Lai, W.; McCauley, E.W.

    1978-01-01

    Table-top model experiments were performed to investigate pressure suppression pool dynamics effects due to a postulated loss-of-coolant accident (LOCA) for the Peachbottom Mark I boiling water reactor containment system. The results guided subsequent conduct of experiments in the 1 / 5 -scale facility and provided new insight into the vertical load function (VLF). Model experiments show an oscillatory VLF with the download typically double-spiked followed by a more gradual sinusoidal upload. The load function contains a high frequency oscillation superimposed on a low frequency one; evidence from measurements indicates that the oscillations are initiated by fluid dynamics phenomena

  9. Model evaluation and optimisation of nutrient removal potential for ...

    African Journals Online (AJOL)

    Performance of sequencing batch reactors for simultaneous nitrogen and phosphorus removal is evaluated by means of model simulation, using the activated sludge model, ASM2d, involving anoxic phosphorus uptake, recently proposed by the IAWQ Task group. The evaluation includes all major process configurations ...

  10. Nutrient and suspended-sediment trends, loads, and yields and development of an indicator of streamwater quality at nontidal sites in the Chesapeake Bay watershed, 1985-2010

    Science.gov (United States)

    Langland, Michael; Blomquist, Joel; Moyer, Douglas; Hyer, Kenneth

    2012-01-01

    The U.S. Geological Survey (USGS) updates information on loads of, and trends in, nutrients and sediment annually to help the Chesapeake Bay Program (CBP) investigators assess progress toward improving water-quality conditions in the Chesapeake Bay and its watershed. CBP scientists and managers have worked since 1983 to improve water quality in the bay. In 2010, the U.S. Environmental Protection Agency (USEPA) established a Total Maximum Daily Load (TMDL) for the Chesapeake Bay. The TMDL specifies nutrient and sediment load allocations that need to be achieved in the watershed to improve dissolved oxygen, water-clarity, and chlorophyll conditions in the bay. The USEPA, USGS, and state and local jurisdictions in the watershed operate a CBP nontidal water-quality monitoring network and associated database that are used to update load and trend information to help assess progress toward reducing nutrient and sediment inputs to the bay. Data collected from the CBP nontidal network were used to estimate loads and trends for two time periods: a long-term period (1985-2010) at 31 "primary" sites (with storm sampling) and a 10-year period (2001-10) at 33 primary sites and 16 "secondary" sites (without storm sampling). In addition, loads at 64 primary sites were estimated for the period 2006 to 2010. Results indicate improving flow-adjusted trends for nitrogen and phosphorus for 1985 to 2010 at most of the sites in the network. For nitrogen, 21 of the 31 sites showed downward (improving) trends, whereas 2 sites showed upward (degrading) trends, and 8 sites showed no trends. The results for phosphorus were similar: 22 sites showed improving trends, 4 sites showed degrading trends, and 5 sites indicated no trends. For sediment, no trend was found at 40 percent of the sites, with 10 sites showing improving trends and 8 sites showing degrading trends. The USGS, working with CBP partners, developed a new water-quality indicator that combines the results of the 10-year trend

  11. Predictive modeling of transient storage and nutrient uptake: Implications for stream restoration

    Science.gov (United States)

    O'Connor, Ben L.; Hondzo, Miki; Harvey, Judson W.

    2010-01-01

    This study examined two key aspects of reactive transport modeling for stream restoration purposes: the accuracy of the nutrient spiraling and transient storage models for quantifying reach-scale nutrient uptake, and the ability to quantify transport parameters using measurements and scaling techniques in order to improve upon traditional conservative tracer fitting methods. Nitrate (NO3–) uptake rates inferred using the nutrient spiraling model underestimated the total NO3– mass loss by 82%, which was attributed to the exclusion of dispersion and transient storage. The transient storage model was more accurate with respect to the NO3– mass loss (±20%) and also demonstrated that uptake in the main channel was more significant than in storage zones. Conservative tracer fitting was unable to produce transport parameter estimates for a riffle-pool transition of the study reach, while forward modeling of solute transport using measured/scaled transport parameters matched conservative tracer breakthrough curves for all reaches. Additionally, solute exchange between the main channel and embayment surface storage zones was quantified using first-order theory. These results demonstrate that it is vital to account for transient storage in quantifying nutrient uptake, and the continued development of measurement/scaling techniques is needed for reactive transport modeling of streams with complex hydraulic and geomorphic conditions.

  12. Predictive Modeling of Transient Storage and Nutrient Uptake: Implications for Stream Restoration

    Energy Technology Data Exchange (ETDEWEB)

    O’Connor, Ben L.; Hondzo, Miki; Harvey, Judson W.

    2010-12-01

    This study examined two key aspects of reactive transport modeling for stream restoration purposes: the accuracy of the nutrient spiraling and transient storage models for quantifying reach-scale nutrient uptake, and the ability to quantify transport parameters using measurements and scaling techniques in order to improve upon traditional conservative tracer fitting methods. Nitrate (NO-3)(NO3-) uptake rates inferred using the nutrient spiraling model underestimated the total NO-3NO3- mass loss by 82%, which was attributed to the exclusion of dispersion and transient storage. The transient storage model was more accurate with respect to the NO-3NO3- mass loss (±20%) and also demonstrated that uptake in the main channel was more significant than in storage zones. Conservative tracer fitting was unable to produce transport parameter estimates for a riffle-pool transition of the study reach, while forward modeling of solute transport using measured/scaled transport parameters matched conservative tracer breakthrough curves for all reaches. Additionally, solute exchange between the main channel and embayment surface storage zones was quantified using first-order theory. These results demonstrate that it is vital to account for transient storage in quantifying nutrient uptake, and the continued development of measurement/scaling techniques is needed for reactive transport modeling of streams with complex hydraulic and geomorphic conditions.

  13. A Verhulst model for microalgae Botryococcus sp. growth and nutrient removal in wastewater

    Science.gov (United States)

    Jamaian, Siti Suhana; Bakeri, Noorhadila Mohd; Sunar, Norshuhaila Mohamed; Gani, Paran

    2017-08-01

    Microalgae Botryococcus sp. is a colonial green alga found in lakes and reservoirs in Malaysia. Previous studies reported that the potential of Botryococcus sp. photosynthesis as a source of fuel. The Botryococcus sp. contains hydrocarbon up to 75% of dry weight, which can be converted into petrol, diesel or turbine fuel or other liquid or gaseous hydrocarbons. Recently, an experimental study was conducted on phycoremediation technology for wastewater using Botryococcus sp. The phycoremediation technology is useful to remove the excess of nutrients such as nitrogen, phosphorus and also have the ability to remove various pollutants from wastewater. This research implements the Verhulst model to estimate the nutrient removal by microalgae Botryococcus sp. from the wastewater. This model has been validated with the experiments of microalgae Botryococcus sp. grown in domestic and palm oil wastewater. The results suggested that microalgae Botryococcus sp. could be cultured in domestic and palm oil wastewater while nutrients are reduced from these wastewaters.

  14. Development of Gene Centric Modeling for Nutrient Cycling

    Science.gov (United States)

    opportunity to participate in the development of a gene-centric model to help predict potential changes in the biogeochemistry of aquatic ecosystems that may arise from anthropogenic stressors and management decisions

  15. Intelligent harmonic load model based on neural networks

    Science.gov (United States)

    Ji, Pyeong-Shik; Lee, Dae-Jong; Lee, Jong-Pil; Park, Jae-Won; Lim, Jae-Yoon

    2007-12-01

    In this study, we developed a RBFNs(Radial Basis Function Networks) based load modeling method with harmonic components. The developed method implemented by using harmonic information as well as fundamental frequency and voltage which are essential input factors in conventional method. Thus, the proposed method makes it possible to effectively estimate load characteristics in power lines with harmonics. The RBFNs have certain advantage such as simple structure and rapid computation ability compared with multilayer perceptron which is extensively applied for load modeling. To show the effectiveness, the proposed method has been intensively tested with various dataset acquired under the different frequency and voltage and compared it with conventional methods such as polynominal 2nd equation method, MLP and RBF without considering harmonic components.

  16. Estimation of tile drainage contribution to streamflow and nutrient loads at the watershed scale based on continuously monitored data.

    Science.gov (United States)

    Arenas Amado, A; Schilling, K E; Jones, C S; Thomas, N; Weber, L J

    2017-09-01

    Nitrogen losses from artificially drained watersheds degrade water quality at local and regional scales. In this study, we used an end-member mixing analysis (EMMA) together with high temporal resolution water quality and streamflow data collected in the 122 km 2 Otter Creek watershed located in northeast Iowa. We estimated the contribution of three end-members (groundwater, tile drainage, and quick flow) to streamflow and nitrogen loads and tested several combinations of possible nitrate concentrations for the end-members. Results indicated that subsurface tile drainage is responsible for at least 50% of the watershed nitrogen load between April 15 and November 1, 2015. Tiles delivered up to 80% of the stream N load while providing only 15-43% of the streamflow, whereas quick flows only marginally contributed to N loading. Data collected offer guidance about areas of the watershed that should be targeted for nitrogen export mitigation strategies.

  17. Computer modeling of road bridge for simulation moving load

    Directory of Open Access Journals (Sweden)

    Miličić Ilija M.

    2016-01-01

    Full Text Available In this paper is shown computational modelling one span road structures truss bridge with the roadway on the upper belt of. Calculation models were treated as planar and spatial girders made up of 1D finite elements with applications for CAA: Tower and Bridge Designer 2016 (2nd Edition. The conducted computer simulations results are obtained for each comparison of the impact of moving load according to the recommendations of the two standards SRPS and AASHATO. Therefore, it is a variant of the bridge structure modeling application that provides Bridge Designer 2016 (2nd Edition identical modeled in an environment of Tower. As important information for the selection of a computer applications point out that the application Bridge Designer 2016 (2nd Edition we arent unable to treat the impacts moving load model under national standard - V600. .

  18. Dynamics Modeling and Control of a Quadrotor with Swing Load

    Directory of Open Access Journals (Sweden)

    S. Sadr

    2014-01-01

    Full Text Available Nowadays, aerial robots or Unmanned Aerial Vehicles (UAV have many applications in civilian and military fields. For example, of these applications is aerial monitoring, picking loads and moving them by different grippers. In this research, a quadrotor with a cable-suspended load with eight degrees of freedom is considered. The purpose is to control the position and attitude of the quadrotor on a desired trajectory in order to move the considered load with constant length of cable. So, the purpose of this research is proposing and designing an antiswing control algorithm for the suspended load. To this end, control and stabilization of the quadrotor are necessary for designing the antiswing controller. Furthermore, this paper is divided into two parts. In the first part, dynamics model is developed using Newton-Euler formulation, and obtained equations are verified in comparison with Lagrange approach. Consequently, a nonlinear control strategy based on dynamic model is used in order to control the position and attitude of the quadrotor. The performance of this proposed controller is evaluated by nonlinear simulations and, finally, the results demonstrate the effectiveness of the control strategy for the quadrotor with suspended load in various maneuvers.

  19. Improved Hypoxia Modeling for Nutrient Control Decisions in the Gulf of Mexico

    Science.gov (United States)

    Habib, Shahid; Pickering, Ken; Tzortziou, Maria; Maninio, Antonio; Policelli, Fritz; Stehr, Jeff

    2011-01-01

    The Gulf of Mexico Modeling Framework is a suite of coupled models linking the deposition and transport of sediment and nutrients to subsequent bio-geo chemical processes and the resulting effect on concentrations of dissolved oxygen in the coastal waters of Louisiana and Texas. Here, we examine the potential benefits of using multiple NASA remote sensing data products within this Modeling Framework for increasing the accuracy of the models and their utility for nutrient control decisions in the Gulf of Mexico. Our approach is divided into three components: evaluation and improvement of (a) the precipitation input data (b) atmospheric constituent concentrations in EPA's air quality/deposition model and (c) the calculation of algal biomass, organic carbon and suspended solids within the water quality/eutrophication models of the framework.

  20. Impact of seasonal changes in nutrient loading on distribution and activity of nitrifiers in a tropical estuary

    Science.gov (United States)

    Vipindas, P. V.; Anas, Abdulaziz; Jayalakshmy, K. V.; Lallu, K. R.; Benny, P. Y.; Shanta, Nair

    2018-02-01

    Estuaries are ecologically important environments, which function as the reception point of nitrogenous inputs of terrestrial and anthropogenic origin. In the present study, we discuss the influence of nutrient characteristics on the distribution and activity of nitrifiers in the water column of Cochin Estuary (CE), a tropical estuary along the southeast Arabian Sea (SEAS). Nitrifying bacteria (i.e. Ammonia- (AOB) and nitrite- (NOB) -oxidizing bacteria), which were enumerated using fluorescent in situ hybridization (FISH), showed marked seasonality while maintaining the abundance within an order of 107 cells L-1. Denaturing Gradient Gel Electrophoresis (DGGE) analysis of AOB exhibited spatio-temporal adaptability without much variation. Nitrification rate in the CE ranged from 2.25 to 426.17 nmol N L-1 h-1 and it was 10-40 fold higher during the pre-monsoon compared with the monsoon. We attributed this increase to high nutrient availability during pre-monsoon due to low flushing rate of the estuary. The study shows that the distribution and activities of nitrifiers in the CE are modulated by the changes in nutrient concentration imparted by the monsoon-driven seasonal variation in river-water discharge and flushing.

  1. Numerical modeling of stresses and buckling loads of isogrid lattice ...

    African Journals Online (AJOL)

    Isogrid composite lattice cylindrical structure with or without skins which consists of a system of ±ϕ (with respect to the shell axis) helical ribs and circumferential ribs, and has no skins or has skins was studied in a numerical method using ANSYS software, where in this model axial compression and/or pressure loads are ...

  2. Modelling and Forecasting Periodic Electric Load for a Metropolitan ...

    African Journals Online (AJOL)

    In this work, three models are used to analyze the electric load capacity of a fast growing urban city and to estimate its future consumption. Ikorodu, the case-study location is a highly populated city whose energy demand is continuously increasing. The ultimate focus of this study is to establish a basis for the comparison of ...

  3. Modeling sources of nutrients in rivers draining into the Bay of Bengal—a scenario analysis

    NARCIS (Netherlands)

    Pedde, Simona; Kroeze, Carolien; Mayorga, Emilio; Seitzinger, Sybil Putnam

    2017-01-01

    We model future trends in river export of nutrients to the Bay of Bengal, and the sources of this pollution. We focus on total nitrogen (TN), total phosphorus (TP), and dissolved silica (DSi) inputs to the Bay of Bengal Large Marine Ecosystem (BOB LME) in the years 2000, 2030, and 2050. In 2000,

  4. Global Nutrient Export from WaterSheds 2 (NEWS 2): Model development and implementation

    NARCIS (Netherlands)

    Mayorga, E.; Seitzinger, S.P.; Harrison, J.A.; Dumont, E.L.; Beusen, A.H.W.; Bouwman, A.F.; Fekete, B.M.; Kroeze, C.; Drecht, van G.

    2010-01-01

    Global NEWS is a global, spatially explicit, multi-element and multi-form model of nutrient exports by rivers. Here we present NEWS 2, the new version of Global NEWS developed as part of a Millennium Ecosystem Assessment scenario implementation from hindcast (1970) to contemporary (2000) and future

  5. Box Model of Freshwater, Salinity and Nutrient in the Delta Mahakam, East Kalimantan

    Directory of Open Access Journals (Sweden)

    Marojahan Simanjuntak

    2011-04-01

    Full Text Available Box Model of Freshwater, Salinity and Nutrient in the Delta Mahakam, East Kalimantan. Research has been conducted in the southern part of the Mahakam Delta, East Kalimantan. Method of measuring temperature, salinity, light transmission and turbidity by using CTD model 603 SBE and current measurement and bathymetry by using ADCP model RDI. Measurement parameters on the nutrient chemistry are based of water samples taken using Nansen bottles from two depths. The purpose of this study to determine the mechanism of freshwater, salinity and nutrient transport from the land of the Mahakam River which interact with seawater by using box models. The results illustrate that the vertical distribution of salinity in the Mahakam Delta has obtained a high stratification, where the freshwater salinity 12.30 psu at the surface of a river flowing toward the sea, and seawater of high salinity 30.07 psu flowing in the direction river under the surface that are separated by a layer of mixture. Freshwater budget of the sea (VSurf obtained for 0,0306 x 109 m3 day-1, and the sea water salinity budget is going into the bottom layer system (VDeep.SOcn-d obtained for 20,727 x 109 psu day-1. While time dilution (Syst obtained for 0.245 day-1 or 5.87 hours. Nutrient budget in the surface layer obtained by the system is autotrophic while in layers near the bottom tend to be heterotrophic

  6. Modeling nutrient sources, transport and management strategies in a coastal watershed, Southeast China.

    Science.gov (United States)

    Zhou, Pei; Huang, Jinliang; Hong, Huasheng

    2018-01-01

    Integrated watershed management requires an analytical model capable of revealing the full range of impacts that would be caused by the uses and developments in the watershed. The SPAtially Referenced Regressions On Watershed Attributes (SPARROW) model was developed in this study to provide empirical estimates of the sources, transport of total nitrogen (TN) and total phosphorus (TP) and to develop nutrient management strategies in the Jiulong River Watershed, southeast China that has enormous influence on the region's ecological safety. We calibrated the model using data related to daily streamflow, monthly TN and TP concentrations in 2014 at 30 locations. The model produced R 2 values for TN with 0.95 and TP with 0.94. It was found that for the entire watershed, TN came from fertilizer application (43%), livestock breeding (39%) and sewage discharge (18%), while TP came from livestock breeding (46%), fertilizer application (46%), and industrial discharge (8%). Fifty-eight percent of the TN and 80% of the TP in upstream reaches are delivered to the outlets of North and West rivers. A scenario analysis with SPARROW was coupled to develop suitable management strategies. Results revealed that controlling nutrient sources was effective in improving water quality. Normally sharp reduction in nutrient sources is not operational feasible. Hence, it is recommended that preventing nutrient on land from entering into the river as a suitable strategy in watershed management. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Phenomenological model for predicting the catabolic potential of an arbitrary nutrient.

    Directory of Open Access Journals (Sweden)

    Samuel M D Seaver

    Full Text Available The ability of microbial species to consume compounds found in the environment to generate commercially-valuable products has long been exploited by humanity. The untapped, staggering diversity of microbial organisms offers a wealth of potential resources for tackling medical, environmental, and energy challenges. Understanding microbial metabolism will be crucial to many of these potential applications. Thermodynamically-feasible metabolic reconstructions can be used, under some conditions, to predict the growth rate of certain microbes using constraint-based methods. While these reconstructions are powerful, they are still cumbersome to build and, because of the complexity of metabolic networks, it is hard for researchers to gain from these reconstructions an understanding of why a certain nutrient yields a given growth rate for a given microbe. Here, we present a simple model of biomass production that accurately reproduces the predictions of thermodynamically-feasible metabolic reconstructions. Our model makes use of only: i a nutrient's structure and function, ii the presence of a small number of enzymes in the organism, and iii the carbon flow in pathways that catabolize nutrients. When applied to test organisms, our model allows us to predict whether a nutrient can be a carbon source with an accuracy of about 90% with respect to in silico experiments. In addition, our model provides excellent predictions of whether a medium will produce more or less growth than another (p<10(-6 and good predictions of the actual value of the in silico biomass production.

  8. Assessment of different polymers and drug loads for fused deposition modeling of drug loaded implants.

    Science.gov (United States)

    Kempin, Wiebke; Franz, Christian; Koster, Lynn-Christine; Schneider, Felix; Bogdahn, Malte; Weitschies, Werner; Seidlitz, Anne

    2017-06-01

    The 3D printing technique of fused deposition modeling® (FDM) has lately come into focus as a potential fabrication technique for pharmaceutical dosage forms and medical devices that allows the preparation of delivery systems with nearly any shape. This is particular promising for implants administered at application sites with a high anatomical variability where an individual shape adaption appears reasonable. In this work different polymers (Eudragit®RS, polycaprolactone (PCL), poly(l-lactide) (PLLA) and ethyl cellulose (EC)) were evaluated with respect to their suitability for FDM of drug loaded implants and their drug release behaviour was evaluated. The fluorescent dye quinine was used as a model drug to visualize drug distribution in filaments and implants. Quinine loaded filaments were produced by solvent casting and subsequent hot melt extrusion (HME) and model implants were printed as hollow cylinders using a standard FDM printer. Parameters were found at which model implants (hollow cylinders, outer diameter 4-5mm, height 3mm) could be produced from all tested polymers. The drug release which was examined by incubation of the printed implants in phosphate buffered saline solution (PBS) pH 7.4 was highly dependent on the used polymer. The fastest relative drug release of approximately 76% in 51days was observed for PCL and the lowest for Eudragit®RS and EC with less than 5% of quinine release in 78 and 100days, respectively. For PCL further filaments were prepared with different quinine loads ranging from 2.5% to 25% and thermal analysis proved the presence of a solid dispersion of quinine in the polymer for all tested concentrations. Increasing the drug load also increased the overall percentage of drug released to the medium since nearly the same absolute amount of quinine remained trapped in PCL at the end of drug release studies. This knowledge is valuable for future developments of printed implants with a desired drug release profile that might be

  9. Testing for time-varying loadings in dynamic factor models

    DEFF Research Database (Denmark)

    Mikkelsen, Jakob Guldbæk

    Abstract: In this paper we develop a test for time-varying factor loadings in factor models. The test is simple to compute and is constructed from estimated factors and residuals using the principal components estimator. The hypothesis is tested by regressing the squared residuals on the squared...... factors. The squared correlation coefficient times the sample size has a limiting chi-squared distribution. The test can be made robust to serial correlation in the idiosyncratic errors. We find evidence for factor loadings variance in over half of the variables in a dataset for the US economy, while...

  10. Hydrothermally treated chitosan hydrogel loaded with copper and zinc particles as a potential micro-nutrient based antimicrobial feed additive

    Directory of Open Access Journals (Sweden)

    Parthiban eRajasekaran

    2015-11-01

    Full Text Available Large-scale use of antibiotics in food animal farms as growth promoters is considered as one of the driving factors behind increasing incidence of microbial resistance. Several alternatives are under investigation to reduce the amount of total antibiotics used in order to avoid any potential transmission of drug resistant microbes to humans through food chain. Copper sulfate and zinc oxide salts are used as feed supplement as they exhibit antimicrobial properties in addition to being micronutrients. However, higher dosage of copper and zinc (often needed for growth promoting effect to animals is not advisable because of potential environmental toxicity arising from excreta. Innovative strategies are needed to utilize the complete potential of trace minerals as growth promoting feed supplements. To this end, we describe here the development and preliminary characterization of hydrothermally treated chitosan as a delivery vehicle for copper and zinc nanoparticles that could act as a micronutrient based antimicrobial feed supplement. Material characterization studies showed that hydrothermal treatment makes a chitosan hydrogel that re-arranged to capture the copper and zinc metal particles. Systemic antimicrobial assays showed that this chitosan biopolymer matrix embedded with copper (57.6 μg/ml and zinc (800 μg/ml reduced the load of model gut-bacteria (target organisms of growth promoting antibiotics such as Escherichia coli, Enterococcus faecalis, Staphylococcus aureus and Lactobacillus fermentum under in vitro conditions. Particularly, the chitosan/copper/zinc hydrogel exhibited significantly higher antimicrobial effect against L. fermentum, one of the primary targets of antibiotic growth promoters. Additionally, the chitosan matrix ameliorated the cytotoxicity levels of metal supplements when screened against a murine macrophage cell line RAW 264.7 and in TE-71, a murine thymic epithelial cell line. In this proof of concept study, we show

  11. Analysis on the uniformly loaded rectangular cross-section cantilever by a modified load-deflection model

    Science.gov (United States)

    Tsai, Shang-Hsi; Wang, Yeng-Tseng; Kan, Heng-Chuan

    2009-02-01

    The load-deflection relationship of the uniformly loaded rectangular cross-section cantilever is analysed by a modified mechanical model, which exhibits its conformity to the physical situation by considering both the tangential and normal surface stresses. The analytical solution of the modelling equation is solved and presented in terms of the first and the second kinds of the Airy functions in association with Scorer's function. The resultant deflection profile contains an inflection point due to the restoring bending moment contributed by the critical surface loadings. The relationships of the tip deflection and the loading scenario are investigated, which reveal the fact that various loading scenarios can result in different deflection profiles, albeit with the same tip deflection. A numerical algorithm is given in the appendix to solve the loading scenario, by which the surface loadings can formally be determined for the designated applications for the devices utilizing the cantilever structure.

  12. Economic MPC based on LPV model for thermostatically controlled loads

    DEFF Research Database (Denmark)

    Zemtsov, Nikita; Hlava, Jaroslav; Frantsuzova, Galina

    2017-01-01

    Rapid increase of the renewable energy share in electricity production requires optimization and flexibility of the power consumption side. Thermostatically controlled loads (TCLs) have a large potential for regulation service provision. Economic model predictive control (MPC) is an advanced....... As a case study, we present control system that minimizes operational cost of swimming pool heating system, where parameters of the model depend on the weather forecast. Simulation results demonstrate that the proposed method is able to deal with this kind of systems....

  13. Recovery of arctic tundra from thermal erosion disturbance is constrained by nutrient accumulation: a modeling analysis.

    Science.gov (United States)

    Pearce, A R; Rastetter, E B; Kwiatkowski, B L; Bowden, W B; Mack, M C; Jiang, Y

    2015-07-01

    Abstract. We calibrated the Multiple Element Limitation (MEL) model to Alaskan arctic tundra to simulate recovery of thermal erosion features (TEFs) caused by permafrost thaw and mass wasting. TEFs could significantly alter regional carbon (C) and nutrient budgets because permafrost soils contain large stocks of soil organic matter (SOM) and TEFs are expected to become more frequent as the climate warms. We simulated recovery following TEF stabilization and did not address initial, short-term losses of C and nutrients during TEF formation. To capture the variability among and within TEFs, we modeled a range of post-stabilization conditions by varying the initial size of SOM stocks and nutrient supply rates. Simulations indicate that nitrogen (N) losses after the TEF stabilizes are small, but phosphorus (P) losses continue. Vegetation biomass recovered 90% of its undisturbed C, N, and P stocks in 100 years using nutrients mineralized from SOM. Because of low litter inputs but continued decomposition, younger SOM continued to be lost for 10 years after the TEF began to recover, but recovered to about 84% of its undisturbed amount in 100 years. The older recalcitrant SOM in mineral soil continued to be lost throughout the 100-year simulation. Simulations suggest that biomass recovery depended on the amount of SOM remaining after disturbance. Recovery was initially limited by the photosynthetic capacity of vegetation but became co-limited by N and P once a plant canopy developed. Biomass and SOM recovery was enhanced by increasing nutrient supplies, but the magnitude, source, and controls on these supplies are poorly understood. Faster mineralization of nutrients from SOM (e.g., by warming) enhanced vegetation recovery but delayed recovery of SOM. Taken together, these results suggest that although vegetation and surface SOM on TEFs recovered quickly (25 and 100 years, respectively), the recovery of deep, mineral soil SOM took centuries and represented a major

  14. INFLUENCE OF INTERMITTENT CYCLIC LOADING ON REINFORCED CONCRETE RESISTANCE MODEL

    Directory of Open Access Journals (Sweden)

    Vasyl Karpiuk

    2017-01-01

    Full Text Available This article describes the study of reinforced concrete span bending structures under conditions of high-level cyclic loading. Previous studies on the development of physical models of bending reinforced concrete element fatigue resistance, cyclic effect of lateral forces, and methods of calculation, are important and appropriate owing to certain features and the essential specificity of the mentioned loading type. These primarily include the nonlinearity of deformation, damage accumulation in the form of fatigue micro- and macro-cracks, and exhausting destruction of construction materials. In this paper, key expressions determining the endurance limits of concrete, longitudinal reinforcement, and anchoring longitudinal reinforcement, which contribute to endurance throughout the entire construction, are considered. Establishing a link between stresses in the elements and deformations in the element under conditions of cyclic loading action is of equal importance because of the presence of cyclic stress-induced creep deformation.

  15. Machine learning based switching model for electricity load forecasting

    International Nuclear Information System (INIS)

    Fan Shu; Chen Luonan; Lee, Weijen

    2008-01-01

    In deregulated power markets, forecasting electricity loads is one of the most essential tasks for system planning, operation and decision making. Based on an integration of two machine learning techniques: Bayesian clustering by dynamics (BCD) and support vector regression (SVR), this paper proposes a novel forecasting model for day ahead electricity load forecasting. The proposed model adopts an integrated architecture to handle the non-stationarity of time series. Firstly, a BCD classifier is applied to cluster the input data set into several subsets by the dynamics of the time series in an unsupervised manner. Then, groups of SVRs are used to fit the training data of each subset in a supervised way. The effectiveness of the proposed model is demonstrated with actual data taken from the New York ISO and the Western Farmers Electric Cooperative in Oklahoma

  16. Springs as Model Systems for Aquatic Ecosystems Ecology: Stoichiometry, Metabolism and Nutrient Limitation

    Science.gov (United States)

    Cohen, M. J.; Nifong, R. L.; Kurz, M. J.; Martin, J. B.; Cropper, W. P.; Korhnak, L. V.

    2013-12-01

    and P gradients, they are more plastic in response to micronutrient variation, particularly for iron and manganese. Expanding on the Droop model framework for understanding nutrient assimilation and plant growth, we discuss these results in the context of nutrient limitation of benthic-dominated lotic systems. We conclude that these spring-fed model systems are N and P saturated, and discuss tools for predicting nutrient limitation and thus eutrophication in flowing waters.

  17. Structural equation model of total phosphorus loads in the Red River of the North Basin, USA and Canada

    Science.gov (United States)

    Ryberg, Karen R.

    2017-01-01

    Attribution of the causes of trends in nutrient loading is often limited to correlation, qualitative reasoning, or references to the work of others. This paper represents efforts to improve causal attribution of water-quality changes. The Red River of the North basin provides a regional test case because of international interest in the reduction of total phosphorus loads and the availability of long-term total phosphorus data and ancillary geospatial data with the potential to explain changes in water quality over time. The objectives of the study are to investigate structural equation modeling methods for application to water-quality problems and to test causal hypotheses related to the drivers of total phosphorus loads over the period 1970 to 2012. Multiple working hypotheses that explain total phosphorus loads and methods for estimating missing ancillary data were developed, and water-quality related challenges to structural equation modeling (including skewed data and scaling issues) were addressed. The model indicates that increased precipitation in season 1 (November–February) or season 2 (March–June) would increase total phosphorus loads in the basin. The effect of agricultural practices on total phosphorus loads was significant, although the effect is about one-third of the effect of season 1 precipitation. The structural equation model representing loads at six sites in the basin shows that climate and agricultural practices explain almost 60% of the annual total phosphorus load in the Red River of the North basin. The modeling process and the unexplained variance highlight the need for better ancillary long-term data for causal assessments.

  18. Nutrient additions in pristine Patagonian Sphagnum bog vegetation: can phosphorus addition alleviate (the effects of) increased nitrogen loads.

    Science.gov (United States)

    Fritz, C; van Dijk, G; Smolders, A J P; Pancotto, V A; Elzenga, T J T M; Roelofs, J G M; Grootjans, A P

    2012-05-01

    Sphagnum-bog ecosystems have a limited capability to retain carbon and nutrients when subjected to increased nitrogen (N) deposition. Although it has been proposed that phosphorus (P) can dilute negative effects of nitrogen by increasing biomass production of Sphagnum mosses, it is still unclear whether P-addition can alleviate physiological N-stress in Sphagnum plants. A 3-year fertilisation experiment was conducted in lawns of a pristine Sphagnum magellanicum bog in Patagonia, where competing vascular plants were practically absent. Background wet deposition of nitrogen was low (≈ 0.1-0.2 g · N · m(-2) · year(-1)). Nitrogen (4 g · N · m(-2) · year(-1)) and phosphorus (1 g · P · m(-2) · year(-1)) were applied, separately and in combination, six times during the growing season. P-addition substantially increased biomass production of Sphagnum. Nitrogen and phosphorus changed the morphology of Sphagnum mosses by enhancing height increment, but lowering moss stem density. In contrast to expectations, phosphorus failed to alleviate physiological stress imposed by excess nitrogen (e.g. amino acid accumulation, N-saturation and decline in photosynthetic rates). We conclude that despite improving growth conditions by P-addition, Sphagnum-bog ecosystems remain highly susceptible to nitrogen additions. Increased susceptibility to desiccation by nutrients may even worsen the negative effects of excess nitrogen especially in windy climates like in Patagonia. © 2011 German Botanical Society and The Royal Botanical Society of the Netherlands.

  19. FEM modelling of soil behaviour under compressive loads

    Science.gov (United States)

    Ungureanu, N.; Vlăduţ, V.; Biriş, S. Şt

    2017-01-01

    Artificial compaction is one of the most dangerous forms of degradation of agricultural soil. Recognized as a phenomenon with multiple negative effects in terms of environment and agricultural production, soil compaction is strongly influenced by the size of external load, soil moisture, size and shape of footprint area, soil type and number of passes. Knowledge of soil behavior under compressive loads is important in order to prevent or minimize soil compaction. In this paper were developed, by means of the Finite Element Method, various models of soil behavior during the artificial compaction produced by the wheel of an agricultural trailer. Simulations were performed on two types of soil (cohesive and non-cohesive) with known characteristics. By applying two loads (4.5 kN and 21 kN) in footprints of different sizes, were obtained the models of the distributions of stresses occuring in the two types of soil. Simulation results showed that soil stresses increase with increasing wheel load and vary with soil type.

  20. Threshold Dynamics of a Stochastic Chemostat Model with Two Nutrients and One Microorganism

    Directory of Open Access Journals (Sweden)

    Jian Zhang

    2017-01-01

    Full Text Available A new stochastic chemostat model with two substitutable nutrients and one microorganism is proposed and investigated. Firstly, for the corresponding deterministic model, the threshold for extinction and permanence of the microorganism is obtained by analyzing the stability of the equilibria. Then, for the stochastic model, the threshold of the stochastic chemostat for extinction and permanence of the microorganism is explored. Difference of the threshold of the deterministic model and the stochastic model shows that a large stochastic disturbance can affect the persistence of the microorganism and is harmful to the cultivation of the microorganism. To illustrate this phenomenon, we give some computer simulations with different intensity of stochastic noise disturbance.

  1. Modelling of usual nutrient intakes : potential impact of the choices programme on nutrient intakes in young dutch adults

    NARCIS (Netherlands)

    Roodenburg, Annet J C; van Ballegooijen, Adriana J; Dötsch-Klerk, Mariska; van der Voet, Hilko; Seidell, Jacob C

    2013-01-01

    INTRODUCTION: The Choices Programme is an internationally applicable nutrient profiling system with nutrition criteria for trans fatty acids (TFA), saturated fatty acids, sodium, added sugar and for some product groups energy and fibre. These criteria determine whether foods are eligible to carry a

  2. Determining Nutrient Requirements For Intensively Managed Loblolly Pine Stands Using the SSAND (Soil Supply and Nutrient Demand) Model

    Science.gov (United States)

    Hector G. Adegbidi; Nicholas B. Comerford; Hua Li; Eric J. Jokela; Nairam F. Barros

    2002-01-01

    Nutrient management represents a central component of intensive silvicultural systems that are designed to increase forest productivity in southern pine stands. Forest soils throughout the South are generally infertile, and fertilizers may be applied one or more times over the course of a rotation. Diagnostic techniques, such as foliar analysis and soil testing are...

  3. Vertebral stress of a cervical spine model under dynamic load.

    Science.gov (United States)

    Sadegh, A M; Tchako, A

    2000-01-01

    The objective of this study is to develop cervical spine models that predict the stresses in each vertebra by taking account of the biodynamic characteristics of the neck. The loads and the moments at the head point (Occipital Condyle) used for the models were determined by the rigid body dynamic response of the head due to G-z acceleration. The experimental data used were collected from the biodynamic responses of human volunteers during an acceleration in the z direction on the drop tower facility at Armstrong Laboratory at Wright Patterson Air Force Base (WPAFB). Three finite element models were developed: an elastic local model, viscoelastic local model and complete viscoelastic model. I-DEAS software was used to create the solid models, the loadings and the boundary conditions. Then, ABAQUS finite element software was employed to solve the models, and thus the stresses on each vertebral level were determined. Beam elements with different properties were employed to simulate the ligaments, articular facets and muscles. The complete viscoelastic model was subjected to 11 cases of loadings ranging from 8 G-z to 20 G-z accelerations. The von Mises and Maximum Principal stress fields, which are good indicators of bone failure, were calculated for all the cases. The results indicated that the maximum stress in all cases increased as the magnitude of the acceleration increased. The stresses in the 10 to 12 G-z cases were comfortably below the injury threshold level. The majority of the maximum stresses occurred in C6 and C4 regions.

  4. Dynamic intelligent cleaning model of dirty electric load data

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiaoxing [State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Chongqing 400044 (China); Sun, Caixin [The Key Laboratory of High Voltage Engineering and Electrical New Technology, Ministry of Education, Electrical Engineering College of Chongqing University, Chongqing 400044 (China)

    2008-04-15

    There are a number of dirty data in the load database derived from the supervisory control and data acquisition (SCADA) system. Thus, the data must be carefully and reasonably adjusted before it is used for electric load forecasting or power system analysis. This paper proposes a dynamic and intelligent data cleaning model based on data mining theory. Firstly, on the basis of fuzzy soft clustering, the Kohonen clustering network is improved to fulfill the parallel calculation of fuzzy c-means soft clustering. Then, the proposed dynamic algorithm can automatically find the new clustering center (the characteristic curve of the data) with the updated sample data; At last, it is composed with radial basis function neural network (RBFNN), and then, an intelligent adjusting model is proposed to identify the dirty data. The rapid and dynamic performance of the model makes it suitable for real time calculation, and the efficiency and accuracy of the model is proved by test results of electrical load data analysis in Chongqing. (author)

  5. Dynamic intelligent cleaning model of dirty electric load data

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Xiaoxing [State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Chongqing 400044 (China)], E-mail: mikezxx@tom.com; Sun Caixin [Key Laboratory of High Voltage Engineering and Electrical New Technology, Ministry of Education, Electrical Engineering College of Chongqing University, Chongqing 400044 (China)

    2008-04-15

    There are a number of dirty data in the load database derived from the supervisory control and data acquisition (SCADA) system. Thus, the data must be carefully and reasonably adjusted before it is used for electric load forecasting or power system analysis. This paper proposes a dynamic and intelligent data cleaning model based on data mining theory. Firstly, on the basis of fuzzy soft clustering, the Kohonen clustering network is improved to fulfill the parallel calculation of fuzzy c-means soft clustering. Then, the proposed dynamic algorithm can automatically find the new clustering center (the characteristic curve of the data) with the updated sample data; At last, it is composed with radial basis function neural network (RBFNN), and then, an intelligent adjusting model is proposed to identify the dirty data. The rapid and dynamic performance of the model makes it suitable for real time calculation, and the efficiency and accuracy of the model is proved by test results of electrical load data analysis in Chongqing.

  6. Dynamic intelligent cleaning model of dirty electric load data

    International Nuclear Information System (INIS)

    Zhang Xiaoxing; Sun Caixin

    2008-01-01

    There are a number of dirty data in the load database derived from the supervisory control and data acquisition (SCADA) system. Thus, the data must be carefully and reasonably adjusted before it is used for electric load forecasting or power system analysis. This paper proposes a dynamic and intelligent data cleaning model based on data mining theory. Firstly, on the basis of fuzzy soft clustering, the Kohonen clustering network is improved to fulfill the parallel calculation of fuzzy c-means soft clustering. Then, the proposed dynamic algorithm can automatically find the new clustering center (the characteristic curve of the data) with the updated sample data; At last, it is composed with radial basis function neural network (RBFNN), and then, an intelligent adjusting model is proposed to identify the dirty data. The rapid and dynamic performance of the model makes it suitable for real time calculation, and the efficiency and accuracy of the model is proved by test results of electrical load data analysis in Chongqing

  7. A model for gas and nutrient exchange in the chorionic vasculature system of the mouse placenta

    Science.gov (United States)

    Mirbod, Parisa; Sled, John

    2015-11-01

    The aim of this study is to develop an analytical model for the oxygen and nutrient transport from the umbilical cord to the small villous capillaries. The nutrient and carbon dioxide removal from the fetal cotyledons in the mouse placental system has also been considered. This model describes the mass transfer between the fetal and the maternal red blood cells in the chorionic arterial vasculature system. The model reveals the detail fetal vasculature system and its geometry and the precise mechanisms of mass transfer through the placenta. The dimensions of the villous capillaries, the total length of the villous trees, the total villi surface area, and the total resistance to mass transport in the fetal villous trees has also been defined. This is the first effort to explain the reason why there are at least 7 lobules in the mouse placenta from the fluid dynamics point of view.

  8. Estimating the carrying capacity of green mussel cultivation by using net nutrient removal model.

    Science.gov (United States)

    Srisunont, Chayarat; Babel, Sandhya

    2016-11-15

    This study aims to evaluate the nutrient removal potential and carrying capacity of green mussel cultivation by using the mass balance model. The developed model takes into consideration the green mussel growth rate, density and chlorophyll a concentration. The data employed in this study were based on culture conditions at Sriracha Fisheries Research Station, Thailand. Results show that net nutrient removal by green mussel is 3302, 380, and 124mg/year/indv for carbon, nitrogen, and phosphorus respectively. The carrying capacity of green mussel cultivation was found to be 300indv/m 2 based on chlorophyll a concentration which will not release phosphorus in the water environment beyond the standard (45μg-PO 4 -3 -P/L). Higher chlorophyll a concentration results in lowered green mussel carrying capacity. This model can assist farm operators with possible management strategies for a sustainable mussel cultivation and protection of the marine environment. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Directional and Spectral Irradiance in Ocean Models: Effects on Simulated Global Phytoplankton, Nutrients, and Primary Production

    Science.gov (United States)

    Gregg, Watson W.; Rousseaux, Cecile S.

    2016-01-01

    The importance of including directional and spectral light in simulations of ocean radiative transfer was investigated using a coupled biogeochemical-circulation-radiative model of the global oceans. The effort focused on phytoplankton abundances, nutrient concentrations and vertically-integrated net primary production. The importance was approached by sequentially removing directional (i.e., direct vs. diffuse) and spectral irradiance and comparing results of the above variables to a fully directionally and spectrally-resolved model. In each case the total irradiance was kept constant; it was only the pathways and spectral nature that were changed. Assuming all irradiance was diffuse had negligible effect on global ocean primary production. Global nitrate and total chlorophyll concentrations declined by about 20% each. The largest changes occurred in the tropics and sub-tropics rather than the high latitudes, where most of the irradiance is already diffuse. Disregarding spectral irradiance had effects that depended upon the choice of attenuation wavelength. The wavelength closest to the spectrally-resolved model, 500 nm, produced lower nitrate (19%) and chlorophyll (8%) and higher primary production (2%) than the spectral model. Phytoplankton relative abundances were very sensitive to the choice of non-spectral wavelength transmittance. The combined effects of neglecting both directional and spectral irradiance exacerbated the differences, despite using attenuation at 500 nm. Global nitrate decreased 33% and chlorophyll decreased 24%. Changes in phytoplankton community structure were considerable, representing a change from chlorophytes to cyanobacteria and coccolithophores. This suggested a shift in community function, from light-limitation to nutrient limitation: lower demands for nutrients from cyanobacteria and coccolithophores favored them over the more nutrient-demanding chlorophytes. Although diatoms have the highest nutrient demands in the model, their

  10. Removal of nutrients and organic pollution load from pulp and paper mill effluent by microalgae in outdoor open pond.

    Science.gov (United States)

    Usha, M T; Sarat Chandra, T; Sarada, R; Chauhan, V S

    2016-08-01

    A mixed culture of microalgae, containing two Scenedesmus species, was analysed to determine its potential in coupling of pulp and paper mill effluent treatment and microalgal cultivation. Laboratory studies suggested that 60% concentration of wastewater was optimum for microalgal cultivation. A maximum of 82% and 75% removal of BOD and COD respectively was achieved with microalgal cultivation in outdoor open pond. By the end of the cultivation period, 65% removal of NO3-N and 71.29% removal of PO4-P was observed. The fatty acid composition of mixed microalgal culture cultivated with effluent showed the palmitic acid, oleic acid, linoleic acid and α-linolenic acid as major fatty acids. The results obtained suggest that pulp and paper mill effluent could be used effectively for cultivation of microalgae to minimise the freshwater and nutrient requirements. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Blast Load Simulator Experiments for Computational Model Validation Report 3

    Science.gov (United States)

    2017-07-01

    establish confidence in the simulation results specific to their intended use. One method for providing experimental data for computational model...walls, to higher blast pressures required to evaluate the performance of protective construction methods . Figure 1. ERDC Blast Load Simulator (BLS... Instrumentation included 3 pressure gauges mounted on the steel calibration plate, 2 pressure gauges mounted in the wall of the BLS, and 25 pressure gauges

  12. A veracity preserving model for synthesizing scalable electricity load profiles

    OpenAIRE

    Huang, Yunyou; Zhan, Jianfeng; Luo, Chunjie; Wang, Lei; Wang, Nana; Zheng, Daoyi; Fan, Fanda; Ren, Rui

    2018-01-01

    Electricity users are the major players of the electric systems, and electricity consumption is growing at an extraordinary rate. The research on electricity consumption behaviors is becoming increasingly important to design and deployment of the electric systems. Unfortunately, electricity load profiles are difficult to acquire. Data synthesis is one of the best approaches to solving the lack of data, and the key is the model that preserves the real electricity consumption behaviors. In this...

  13. Comparison of Building Energy Modeling Programs: Building Loads

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Dandan [Tsinghua Univ., Beijing (China); Hong, Tianzhen [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Yan, Da [Tsinghua Univ., Beijing (China); Wang, Chuang [Tsinghua Univ., Beijing (China)

    2012-06-01

    This technical report presented the methodologies, processes, and results of comparing three Building Energy Modeling Programs (BEMPs) for load calculations: EnergyPlus, DeST and DOE-2.1E. This joint effort, between Lawrence Berkeley National Laboratory, USA and Tsinghua University, China, was part of research projects under the US-China Clean Energy Research Center on Building Energy Efficiency (CERC-BEE). Energy Foundation, an industrial partner of CERC-BEE, was the co-sponsor of this study work. It is widely known that large discrepancies in simulation results can exist between different BEMPs. The result is a lack of confidence in building simulation amongst many users and stakeholders. In the fields of building energy code development and energy labeling programs where building simulation plays a key role, there are also confusing and misleading claims that some BEMPs are better than others. In order to address these problems, it is essential to identify and understand differences between widely-used BEMPs, and the impact of these differences on load simulation results, by detailed comparisons of these BEMPs from source code to results. The primary goal of this work was to research methods and processes that would allow a thorough scientific comparison of the BEMPs. The secondary goal was to provide a list of strengths and weaknesses for each BEMP, based on in-depth understandings of their modeling capabilities, mathematical algorithms, advantages and limitations. This is to guide the use of BEMPs in the design and retrofit of buildings, especially to support China’s building energy standard development and energy labeling program. The research findings could also serve as a good reference to improve the modeling capabilities and applications of the three BEMPs. The methodologies, processes, and analyses employed in the comparison work could also be used to compare other programs. The load calculation method of each program was analyzed and compared to

  14. Multi-proxy evidence of long-term changes in ecosystem structure in a Danish marine estuary, linked to increased nutrient loading

    DEFF Research Database (Denmark)

    Ellegaard, Marianne; Clarke, A.L.; Reuss, Nina Steenberg

    2006-01-01

    and prompting debate on the causes. This paper reports a multi-proxy survey of 210Pb-dated sediment cores from the anoxic basin. Analyses of diatoms, dinoflagellates, pigments and geochemical proxies were used to determine changes in ecosystem structure over the past 100 years. The aim was to establish ‘base......-line conditions', for management purposes, of the biological structure prior to 1900, and to examine possible causes of changes observed. Geochemical proxies total nitrogen (TN), total carbon (TC) and biogenic silica (BSi) were consistently high throughout the sediment record. Increased concentrations of pigments...... and natural isotopes (d13C, d15N) suggested increasing production and nutrient loading. The main changes in the biological proxies occurred between 1915 and the 1940s, and indicated that the estuary has been somewhat eutrophic since 1900, but that the eutrophication process increased over the past 100 years...

  15. Optimisation models and solution methods for load management

    International Nuclear Information System (INIS)

    Gustafsson, Stig-Inge; Roennqvist, Mikael; Claesson, Marcus

    2001-02-01

    The electricity market in Sweden has changed during recent years. Electricity for industrial use can nowadays be purchased from a number of competing electricity suppliers. Hence, the price for each kilowatt-hour is significantly lower than just two years ago and the interest for electricity conservation measures has declined. Part of the electricity tariff is, however, almost the same as before, i.e. the demand cost expressed in Swedish Kronor, SEK, for each kilowatt. This has put focus on load management measures in order to decrease this specific cost. Saving one kWh might lead to monetary savings between 0.22 to 914 SEK and this paper shows how to save only those kWh which really save money. A load management system has been installed in a small carpentry factory and the device can turn off equipment due to a certain priority and for a number of minutes each hour. The question is now, what level on the electricity load is optimal in a strict mathematical sense, i.e. how many kW should be set in the load management computer in order to get the best profitability? In this paper we develop a mathematical model which can be used both as a tool to find a best profitable subscription level and as a tool to control the turn of choices. Numerical results from a case study are presented

  16. Modelling mussel growth in ecosystems with low suspended matter loads

    Science.gov (United States)

    Duarte, P.; Fernández-Reiriz, M. J.; Filgueira, R.; Labarta, U.

    2010-10-01

    Over the last decades a large number of bivalve growth models were described in the literature with most emphasis on cultivated species with important economic value. These models describe the rates of energy absorption and utilization as a function of environmental conditions. Some of the most important issues in bivalve modelling are water pumping, filtration, pre-ingestive rejection/pseudofaeces production and ingestion of living and non-living organic and inorganic matter. According to some authors, bivalve suspension-feeders may selectively ingest and/or digest different food items whilst making adjustments to maximize the utilization of chlorophyll rich particles. In clear water ecosystems such as the Galician Rias (total particulate matter ( TPM) TPM loads. The main objectives of this work were to develop, implement and calibrate an Individual Based Model of mussel growth, configured and parameterized for the environmental conditions of ecosystems with low suspended matter loads such as the Galician Rias. Model runs were made for a large number of individual mussels, each with a random parameter set, selected among possible parameter ranges reported in the literature, allowing a quick model calibration and an evaluation of those parameters explaining most of the variance in predicted mussel growth. Obtained results provide a useful feedback for upcoming experimental work where efforts should be concentrated on accurate estimates of these more influential parameters to improve model results.

  17. Effects of simultaneous ozone exposure and nitrogen loads on carbohydrate concentrations, biomass, growth, and nutrient concentrations of young beech trees (Fagus sylvatica)

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, V.F.D. [Institute for Applied Plant Biology, Sandgrubenstr. 25/27, 4124 Schoenenbuch (Switzerland)]. E-mail: vera.thomas@iap.ch; Braun, S. [Institute for Applied Plant Biology, Sandgrubenstr. 25/27, 4124 Schoenenbuch (Switzerland); Flueckiger, W. [Institute for Applied Plant Biology, Sandgrubenstr. 25/27, 4124 Schoenenbuch (Switzerland)

    2006-09-15

    Beech seedlings were grown under different nitrogen fertilisation regimes (0, 20, 40, and 80 kg N ha{sup -1} yr{sup -1}) for three years and were fumigated with either charcoal-filtered (F) or ambient air (O{sub 3}). Nitrogen fertilisation increased leaf necroses, aphid infestations, and nutrient ratios in the leaves (N:P and N:K), as a result of decreased phosphorus and potassium concentrations. For plant growth, biomass accumulation, and starch concentrations, a positive nitrogen effect was found, but only for fertilisations of up to 40 kg N ha{sup -1} yr{sup -1}. The highest nitrogen load, however, reduced leaf area, leaf water content, growth, biomass accumulation, and starch concentrations, whereas soluble carbohydrate concentrations were enhanced. The ozone fumigation resulted in reduced leaf area, leaf water content, shoot growth, root biomass accumulation, and decreased starch, phosphorus, and potassium concentrations, increasing the N:P and N:K ratios. A combined effect of the two pollutants was detected for the leaf area and the shoot elongation, where ozone fumigation amplified the nitrogen effects. - The effects of nitrogen and ozone on growth, carbohydrate concentrations, and nutrients are mainly additive.

  18. Dynamic root growth and architecture responses to limiting nutrient availability: linking physiological models and experimentation.

    Science.gov (United States)

    Postma, Johannes A; Schurr, Ulrich; Fiorani, Fabio

    2014-01-01

    In recent years the study of root phenotypic plasticity in response to sub-optimal environmental factors and the genetic control of these responses have received renewed attention. As a path to increased productivity, in particular for low fertility soils, several applied research projects worldwide target the improvement of crop root traits both in plant breeding and biotechnology contexts. To assist these tasks and address the challenge of optimizing root growth and architecture for enhanced mineral resource use, the development of realistic simulation models is of great importance. We review this research field from a modeling perspective focusing particularly on nutrient acquisition strategies for crop production on low nitrogen and low phosphorous soils. Soil heterogeneity and the dynamics of nutrient availability in the soil pose a challenging environment in which plants have to forage efficiently for nutrients in order to maintain their internal nutrient homeostasis throughout their life cycle. Mathematical models assist in understanding plant growth strategies and associated root phenes that have potential to be tested and introduced in physiological breeding programs. At the same time, we stress that it is necessary to carefully consider model assumptions and development from a whole plant-resource allocation perspective and to introduce or refine modules simulating explicitly root growth and architecture dynamics through ontogeny with reference to key factors that constrain root growth. In this view it is important to understand negative feedbacks such as plant-plant competition. We conclude by briefly touching on available and developing technologies for quantitative root phenotyping from lab to field, from quantification of partial root profiles in the field to 3D reconstruction of whole root systems. Finally, we discuss how these approaches can and should be tightly linked to modeling to explore the root phenome. © 2013.

  19. Prediction of storm transfers and annual loads with data-based mechanistic models using high-frequency data

    Science.gov (United States)

    Ockenden, Mary C.; Tych, Wlodek; Beven, Keith J.; Collins, Adrian L.; Evans, Robert; Falloon, Peter D.; Forber, Kirsty J.; Hiscock, Kevin M.; Hollaway, Michael J.; Kahana, Ron; Macleod, Christopher J. A.; Villamizar, Martha L.; Wearing, Catherine; Withers, Paul J. A.; Zhou, Jian G.; Benskin, Clare McW. H.; Burke, Sean; Cooper, Richard J.; Freer, Jim E.; Haygarth, Philip M.

    2017-12-01

    Excess nutrients in surface waters, such as phosphorus (P) from agriculture, result in poor water quality, with adverse effects on ecological health and costs for remediation. However, understanding and prediction of P transfers in catchments have been limited by inadequate data and over-parameterised models with high uncertainty. We show that, with high temporal resolution data, we are able to identify simple dynamic models that capture the P load dynamics in three contrasting agricultural catchments in the UK. For a flashy catchment, a linear, second-order (two pathways) model for discharge gave high simulation efficiencies for short-term storm sequences and was useful in highlighting uncertainties in out-of-bank flows. A model with non-linear rainfall input was appropriate for predicting seasonal or annual cumulative P loads where antecedent conditions affected the catchment response. For second-order models, the time constant for the fast pathway varied between 2 and 15 h for all three catchments and for both discharge and P, confirming that high temporal resolution data are necessary to capture the dynamic responses in small catchments (10-50 km2). The models led to a better understanding of the dominant nutrient transfer modes, which will be helpful in determining phosphorus transfers following changes in precipitation patterns in the future.

  20. Prediction of storm transfers and annual loads with data-based mechanistic models using high-frequency data

    Directory of Open Access Journals (Sweden)

    M. C. Ockenden

    2017-12-01

    Full Text Available Excess nutrients in surface waters, such as phosphorus (P from agriculture, result in poor water quality, with adverse effects on ecological health and costs for remediation. However, understanding and prediction of P transfers in catchments have been limited by inadequate data and over-parameterised models with high uncertainty. We show that, with high temporal resolution data, we are able to identify simple dynamic models that capture the P load dynamics in three contrasting agricultural catchments in the UK. For a flashy catchment, a linear, second-order (two pathways model for discharge gave high simulation efficiencies for short-term storm sequences and was useful in highlighting uncertainties in out-of-bank flows. A model with non-linear rainfall input was appropriate for predicting seasonal or annual cumulative P loads where antecedent conditions affected the catchment response. For second-order models, the time constant for the fast pathway varied between 2 and 15 h for all three catchments and for both discharge and P, confirming that high temporal resolution data are necessary to capture the dynamic responses in small catchments (10–50 km2. The models led to a better understanding of the dominant nutrient transfer modes, which will be helpful in determining phosphorus transfers following changes in precipitation patterns in the future.

  1. Numerical modeling of intraplate seismicity with a deformable loading plate

    Science.gov (United States)

    So, B. D.; Capitanio, F. A.

    2017-12-01

    We use finite element modeling to investigate on the stress loading-unloading cycles and earthquakes occurrence in the plate interiors, resulting from the interactions of tectonic plates along their boundary. We model a visco-elasto-plastic plate embedding a single or multiple faults, while the tectonic stress is applied along the plate boundary by an external loading visco-elastic plate, reproducing the tectonic setting of two interacting lithospheres. Because the two plates deform viscously, the timescale of stress accumulation and release on the faults is self-consistently determined, from the boundary to the interiors, and seismic recurrence is an emerging feature. This approach overcomes the constraints on recurrence period imposed by stress (stress-drop) and velocity boundary conditions, while here it is unconstrained. We illustrate emerging macroscopic characteristics of this system, showing that the seismic recurrence period τ becomes shorter as Γ and Θ decreases, where Γ = ηI/ηL the viscosity ratio of the viscosities of the internal fault-embedded to external loading plates, respectively, and Θ = σY/σL the stress ratio of the elastic limit of the fault to far-field loading stress. When the system embeds multiple, randomly distributed faults, stress transfer results in recurrence period deviations, however the time-averaged recurrence period of each fault show the same dependence on Γ and Θ, illustrating a characteristic collective behavior. The control of these parameters prevails even when initial pre-stress was randomly assigned in terms of the spatial arrangement and orientation on the internal plate, mimicking local fluctuations. Our study shows the relevance of macroscopic rheological properties of tectonic plates on the earthquake occurrence in plate interiors, as opposed to local factors, proposing a viable model for the seismic behavior of continent interiors in the context of large-scale, long-term deformation of interacting tectonic

  2. Climate Variability over India and Bangladesh from the Perturbed UK Met Office Hadley Model: Impacts on Flow and Nutrient Fluxes in the Ganges Delta System

    Science.gov (United States)

    Whitehead, P. G.; Caesar, J.; Crossman, J.; Barbour, E.; Ledesma, J.; Futter, M. N.

    2015-12-01

    A semi-distributed flow and water quality model (INCA- Integrated Catchments Model) has been set up for the whole of the Ganges- Brahmaputra- Meghna (GBM) River system in India and Bangladesh. These massive rivers transport large fluxes of water and nutrients into the Bay of Bengal via the GBM Delta system in Bangladesh. Future climate change will impact these fluxes with changing rainfall, temperature, evapotranspiration and soil moisture deficits being altered in the catchment systems. In this study the INCA model has been used to assess potential impacts of climate change using the UK Met Office Hadley Centre GCM model linked to a regionally coupled model of South East Asia, covering India and Bangladesh. The Hadley Centre model has been pururbed by varying the parameters in the model to generate 17 realisations of future climates. Some of these reflect expected change but others capture the more extreme potential behaviour of future climate conditions. The 17 realisations have been used to drive the INCA Flow and Nitrogen model inorder to generate downstream times series of hydrology and nitrate- nitrogen. The variability of the climates on these fluxes are investigated and and their likley impact on the Bay of Begal Delta considered. Results indicate a slight shift in the monsoon season with increased wet season flows and increased temperatures which alter nutrient fluxes. Societal Importance to Stakeholders The GBM Delta supports one of the most densely populated regions of people living in poverty, who rely on ecosystem services provided by the Delta for survival. These ecosystem services are dependent upon fluxes of water and nutrients. Freshwater for urban, agriculture, and aquaculture requirements are essential to livelihoods. Nutrient loads stimulate estuarine ecosystems, supporting fishing stocks, which contribute significantly the economy of Bangladesh. Thus the societal importance of upstream climate driven change change in Bangladesh are very

  3. Preliminary Study of Soil Available Nutrient Simulation Using a Modified WOFOST Model and Time-Series Remote Sensing Observations

    OpenAIRE

    Zhiqiang Cheng; Jihua Meng; Yanyou Qiao; Yiming Wang; Wenquan Dong; Yanxin Han

    2018-01-01

    The approach of using multispectral remote sensing (RS) to estimate soil available nutrients (SANs) has been recently developed and shows promising results. This method overcomes the limitations of commonly used methods by building a statistical model that connects RS-based crop growth and nutrient content. However, the stability and accuracy of this model require improvement. In this article, we replaced the statistical model by integrating the World Food Studies (WOFOST) model and time seri...

  4. Ecosystem modelling of carbon, nutrients and radionuclides in lake Eckarfjaerden, Sweden

    Energy Technology Data Exchange (ETDEWEB)

    Kumblad, L.; Andersson, E.; Wijnbladh, E.; Kautsky, U. [Stockholm Univ., Dept. of Systems Ecology (Sweden)

    2004-07-01

    During the next few years, the Swedish Nuclear Fuel and Waste Management Co (SKB) perform site investigations at two sites in Sweden for a future underground repository of spent nuclear fuel. For the safety assessment of the repository, methods based on systems and landscape ecology was developed to understand the radionuclide flow at the site using site-specific data. In this part of the project a mechanistic mass-balance model for carbon and nutrients between the components of the Lake Eckarfjaerden was developed. The lake has been thoroughly monitored for water chemistry, biota, geo-morphometry and water flows etc. to enable site-specific process-oriented dose modelling. The modelling of carbon and nutrients was based on ecosystem processes such as primary production, respiration and consumption. C-14 was modelled in proportion to the circulation of non-radioactive carbon in the ecosystem, whereas the modelling of other radionuclides included two radionuclide specific mechanisms in addition to the ecological processes. The radionuclide uptake by plants was modelled with an uptake function based on conventional uptake factors related to the primary production rate of the plants. The transfer of radionuclides from plants to animals in the ecosystem was modelled in proportion to the consumption rate of the grazer/predator, the concentration in the plant/prey and a specific radionuclide excretion rate related to the rate of carbon and nutrients excreted. The results were compared with traditional dose assessment models. We believe that this method has a large potential to be used either directly in assessment modelling or to produce site-specific transfer factors for more conventional models, which is especially valuable when future changes of the environment needs to be taken into account. (author)

  5. Modelling nutrient exchange at the sediment water interface of river systems

    Science.gov (United States)

    Thouvenot, Marie; Billen, Gilles; Garnier, Josette

    2007-07-01

    SummaryIn-stream benthic processes can play a significant role on the water quality of overlying waters flowing through a river network. In order to better understand and quantify the fate of nutrients (nitrogen, phosphorus and silica) during their travel through the river continuum, a deterministic benthic sub-model was developed with the purpose of being connected to a drainage network model. This benthic sub-model resolves the differential equations representing early diagenesis in the sediment, linking the sedimentation rate of organic matter onto the sediment to the resulting flux of nutrients across the sediment-water interface. The model has been developed for conditions where sedimentation prevails as well as for situations where net erosion prevents the built-up of a significant sediment layer and where only a biofilm can develop, attached to solid substrates. The benthic model was tested independently of the main water column biological-hydrological model to which it is intended to be coupled. For this, three case studies were chosen from the literature representing various sedimentation/erosion conditions: the 8th order river Seine (France), the water storage basin of Méry s/Oise (France), and the headwater stream Orneau (Belgium). The general benthic model has been validated for ammonium, nitrate, oxygen and phosphorus fluxes across the sediment-water interface. The capability of the model to correctly predict the observed nutrients profiles within the sediment was also validated for organic carbon, ammonium and phosphorus. An uncertainty analysis showed that using two modelling objectives (observed fluxes and concentration profiles in the sediment) strongly reduces the uncertainty in parameters calibration. A sensitivity analysis illustrated the complexity of the interacting reactions driving each variable, and justifies the usefulness of the model as a tool for understanding and predicting the behaviour of the benthic compartment of river systems.

  6. A mechanistic soil biogeochemistry model with explicit representation of microbial and macrofaunal activities and nutrient cycles

    Science.gov (United States)

    Fatichi, Simone; Manzoni, Stefano; Or, Dani; Paschalis, Athanasios

    2016-04-01

    The potential of a given ecosystem to store and release carbon is inherently linked to soil biogeochemical processes. These processes are deeply connected to the water, energy, and vegetation dynamics above and belowground. Recently, it has been advocated that a mechanistic representation of soil biogeochemistry require: (i) partitioning of soil organic carbon (SOC) pools according to their functional role; (ii) an explicit representation of microbial dynamics; (iii) coupling of carbon and nutrient cycles. While some of these components have been introduced in specialized models, they have been rarely implemented in terrestrial biosphere models and tested in real cases. In this study, we combine a new soil biogeochemistry model with an existing model of land-surface hydrology and vegetation dynamics (T&C). Specifically the soil biogeochemistry component explicitly separates different litter pools and distinguishes SOC in particulate, dissolved and mineral associated fractions. Extracellular enzymes and microbial pools are explicitly represented differentiating the functional roles of bacteria, saprotrophic and mycorrhizal fungi. Microbial activity depends on temperature, soil moisture and litter or SOC stoichiometry. The activity of macrofauna is also modeled. Nutrient dynamics include the cycles of nitrogen, phosphorous and potassium. The model accounts for feedbacks between nutrient limitations and plant growth as well as for plant stoichiometric flexibility. In turn, litter input is a function of the simulated vegetation dynamics. Root exudation and export to mycorrhiza are computed based on a nutrient uptake cost function. The combined model is tested to reproduce respiration dynamics and nitrogen cycle in few sites where data were available to test plausibility of results across a range of different metrics. For instance in a Swiss grassland ecosystem, fine root, bacteria, fungal and macrofaunal respiration account for 40%, 23%, 33% and 4% of total belowground

  7. Nutrient (N, P, Si) transfers in the subtropical Red River system (China and Vietnam): Modelling and budget of nutrient sources and sinks

    Science.gov (United States)

    Le, Thi Phuong Quynh; Gilles, Billen; Garnier, Josette; Sylvain, Théry; Denis, Ruelland; Anh, Nghiem Xuan; Minh, Chau Van

    2010-02-01

    The Red River system, which has a population density that varies from 80 to over 1000 inhabitants km -2 in the different sectors of its watershed, is a typical example of a subtropical system experiencing high human pressure. A monthly survey of nutrient concentration was conducted at the outlet of the three main tributaries (Da, Thao and Lo) and at Hanoi on the main branch of the Red River in the upper part of the delta. Samples from headwater streams or irrigation channels draining homogeneous land use classes also were analysed. A GIS database describing the characteristics of the watershed in terms of morphology, climate, land use and population has been established. This served as the basis for implementing the Seneque/Riverstrahler model, which allowed calculation of nutrient transfers and transformations along the whole drainage network of the Red River system. The model was validated using the measured nutrient concentrations obtained during the survey and was used to establish an overall description and a comprehensive budget of nutrient transfer, retention and delivery for the three main sub-basins and the upper part of the delta upstream from Hanoi.

  8. Modeling nutrient retention at the watershed scale: Does small stream research apply to the whole river network?

    Science.gov (United States)

    Aguilera, Rosana; Marcé, Rafael; Sabater, Sergi

    2013-06-01

    are conveyed from terrestrial and upstream sources through drainage networks. Streams and rivers contribute to regulate the material exported downstream by means of transformation, storage, and removal of nutrients. It has been recently suggested that the efficiency of process rates relative to available nutrient concentration in streams eventually declines, following an efficiency loss (EL) dynamics. However, most of these predictions are based at the reach scale in pristine streams, failing to describe the role of entire river networks. Models provide the means to study nutrient cycling from the stream network perspective via upscaling to the watershed the key mechanisms occurring at the reach scale. We applied a hybrid process-based and statistical model (SPARROW, Spatially Referenced Regression on Watershed Attributes) as a heuristic approach to describe in-stream nutrient processes in a highly impaired, high stream order watershed (the Llobregat River Basin, NE Spain). The in-stream decay specifications of the model were modified to include a partial saturation effect in uptake efficiency (expressed as a power law) and better capture biological nutrient retention in river systems under high anthropogenic stress. The stream decay coefficients were statistically significant in both nitrate and phosphate models, indicating the potential role of in-stream processing in limiting nutrient export. However, the EL concept did not reliably describe the patterns of nutrient uptake efficiency for the concentration gradient and streamflow values found in the Llobregat River basin, posing in doubt its complete applicability to explain nutrient retention processes in stream networks comprising highly impaired rivers.

  9. Multi-nutrient, multi-group model of present and future oceanic phytoplankton communities

    Directory of Open Access Journals (Sweden)

    E. Litchman

    2006-01-01

    Full Text Available Phytoplankton community composition profoundly affects patterns of nutrient cycling and the dynamics of marine food webs; therefore predicting present and future phytoplankton community structure is crucial to understand how ocean ecosystems respond to physical forcing and nutrient limitations. We develop a mechanistic model of phytoplankton communities that includes multiple taxonomic groups (diatoms, coccolithophores and prasinophytes, nutrients (nitrate, ammonium, phosphate, silicate and iron, light, and a generalist zooplankton grazer. Each taxonomic group was parameterized based on an extensive literature survey. We test the model at two contrasting sites in the modern ocean, the North Atlantic (North Atlantic Bloom Experiment, NABE and subarctic North Pacific (ocean station Papa, OSP. The model successfully predicts general patterns of community composition and succession at both sites: In the North Atlantic, the model predicts a spring diatom bloom, followed by coccolithophore and prasinophyte blooms later in the season. In the North Pacific, the model reproduces the low chlorophyll community dominated by prasinophytes and coccolithophores, with low total biomass variability and high nutrient concentrations throughout the year. Sensitivity analysis revealed that the identity of the most sensitive parameters and the range of acceptable parameters differed between the two sites. We then use the model to predict community reorganization under different global change scenarios: a later onset and extended duration of stratification, with shallower mixed layer depths due to increased greenhouse gas concentrations; increase in deep water nitrogen; decrease in deep water phosphorus and increase or decrease in iron concentration. To estimate uncertainty in our predictions, we used a Monte Carlo sampling of the parameter space where future scenarios were run using parameter combinations that produced acceptable modern day outcomes and the

  10. Evaluation of Karst Soil Erosion and Nutrient Loss Based on RUSLE Model in Guizhou Province

    Science.gov (United States)

    Zeng, Cheng; Li, Yangbing; Bai, Xiaoyong; Luo, Guangjie

    2018-01-01

    Based on GIS technology and RUSLE model, the spatial variation characteristics of soil erosion were analyzed in karst areas, and the relationship between soil erosion and soil nutrient loss was discussed. The results showed that the soil differences in spatial variation between nutrient losses. The results illustrate the total soil erosion in is 10316.31 × 104t • a-1, accounting for 84.95% of the total land area in Guizhou Province. The spatial distribution of soil erosion showing the characteristics of the southeast to the northwest strip. The annual average soil erosion modulu is 691.94 t • km-2 • a-1, of which karst is 720.28t • km-2 • a-1 and non-karst is 689.53 t • km-2 • a-1. The total nutrient losses such as soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP) and total potassium (TK) were 596.72 × 104t • a-1 due to soil erosion, and SOC, TN and TP and TK were 38.13, 1.61, 0.41 and 14.70t • km-2 • a-1, respectively. The average amount of loss and total loss are the largest in non-karst, and four kinds of nutrient is the smallest in karst gorge. The spatial variation of soil erosion in the study area is the process of increasing the erosion area with the increase of the erosion rate, and the difference of the spatial distribution of soil erosion determines the spatial distribution of soil nutrient loss.

  11. Statistical modelling of variability in sediment-water nutrient and oxygen fluxes

    Science.gov (United States)

    Serpetti, Natalia; Witte, Ursula; Heath, Michael

    2016-06-01

    Organic detritus entering, or produced, in the marine environment is re-mineralised to inorganic nutrient in the seafloor sediments. The flux of dissolved inorganic nutrient between the sediment and overlying water column is a key process in the marine ecosystem, which binds the biogeochemical sub-system to the living food web. These fluxes are potentially affected by a wide range of physical and biological factors and disentangling these is a significant challenge. Here we develop a set of General Additive Models (GAM) of nitrate, nitrite, ammonia, phosphate, silicate and oxygen fluxes, based on a year-long campaign of field measurements off the north-east coast of Scotland. We show that sediment grain size, turbidity due to sediment re-suspension, temperature, and biogenic matter content were the key factors affecting oxygen consumption, ammonia and silicate fluxes. However, phosphate fluxes were only related to suspended sediment concentrations, whilst nitrate fluxes showed no clear relationship to any of the expected drivers of change, probably due to the effects of denitrification. Our analyses show that the stoichiometry of nutrient regeneration in the ecosystem is not necessarily constant and may be affected by combinations of processes. We anticipate that our statistical modelling results will form the basis for testing the functionality of process-based mathematical models of whole-sediment biogeochemistry.

  12. Finite element model for nutrient distribution analysis of a hollow fiber membrane bioreactor.

    Science.gov (United States)

    Unnikrishnan, G U; Unnikrishnan, V U; Reddy, J N

    2012-02-01

    Hollow fiber membrane bioreactors (HFMB) are extensively used for the development of tissue substitutes for bones and cartilages. In an HFMB, the nutrient transport is dependent on the material properties of the porous scaffold and fiber membrane and also on the fluid flow through the hollow fiber. The difficulty in obtaining real-time data along with the presence of large number of variables in experimental studies have lead to increased application of computational models for the performance analysis of bioreactors. A major difficulty in the computational analysis of HFMB is the modeling of the interactions at the fluid and porous scaffold interfaces, which has often been neglected or incorporated using specific boundary conditions. In this study, a new FEM is developed to analyze the fluid flow in the fluid-porous region with the interface coupled directly into the FEM. Distribution of nutrients in the bioreactor is studied by coupling mass transport equations to the fluid-porous finite element framework. The new model is implemented to study the influence of permeability, cell density, and flow rate on the nutrient concentration distribution in the HFMB. The developed computational framework is an ideal tool to study fluid flow through porous-open channels and can also be used for the design of bioreactors for optimal tissue growth. Copyright © 2011 John Wiley & Sons, Ltd.

  13. Loading models for electric vehicles; Lademodelle fuer Elektrofahrzeuge

    Energy Technology Data Exchange (ETDEWEB)

    Mezger, Tomas [Forschungsstelle fuer Energiewirtschaft e.V., Muenchen (Germany)

    2011-07-01

    About 5 to 7 million electric vehicles have adverse effects on the electricity grid. Thus, there is a need to develop optimized loading concepts, which generate an added value both for the energy industry as well as for the vehicle owners. A two-stage analysis method is used for this. Within the first step it is examined, how defined fleet of electric vehicles can be loaded optimally with electricity taking into account the specific vehicle usage. In the second step, the charging models are again evaluated from a user perspective. The impact of the driving behavior and charge characteristics on the aging of the battery are considered specifically. Charging possibilities are identified in order to increase the battery life.

  14. Water Quality Protection from Nutrient Pollution: Case ...

    Science.gov (United States)

    Water bodies and coastal areas around the world are threatened by increases in upstream sediment and nutrient loads, which influence drinking water sources, aquatic species, and other ecologic functions and services of streams, lakes, and coastal water bodies. For example, increased nutrient fluxes from the Mississippi River Basin have been linked to increased occurrences of seasonal hypoxia in northern Gulf of Mexico. Lake Erie is another example where in the summer of 2014 nutrients, nutrients, particularly phosphorus, washed from fertilized farms, cattle feedlots, and leaky septic systems; caused a severe algae bloom, much of it poisonous; and resulted in the loss of drinking water for a half-million residents. Our current management strategies for point and non-point source nutrient loadings need to be improved to protect and meet the expected increased future demands of water for consumption, recreation, and ecological integrity. This presentation introduces management practices being implemented and their effectiveness in reducing nutrient loss from agricultural fields, a case analysis of nutrient pollution of the Grand Lake St. Marys and possible remedies, and ongoing work on watershed modeling to improve our understanding on nutrient loss and water quality. Presented at the 3rd International Conference on Water Resource and Environment.

  15. On the Influence of Weather Forecast Errors in Short-Term Load Forecasting Models

    OpenAIRE

    Fay, D.; Ringwood, John; Condon, M.

    2004-01-01

    Weather information is an important factor in load forecasting models. This weather information usually takes the form of actual weather readings. However, online operation of load forecasting models requires the use of weather forecasts, with associated weather forecast errors. A technique is proposed to model weather forecast errors to reflect current accuracy. A load forecasting model is then proposed which combines the forecasts of several load forecasting models. This approach allows the...

  16. Modeling long-term changes in tundra carbon balance following wildfire, climate change, and potential nutrient addition.

    Science.gov (United States)

    Jiang, Yueyang; Rastetter, Edward B; Shaver, Gaius R; Rocha, Adrian V; Zhuang, Qianlai; Kwiatkowski, Bonnie L

    2017-01-01

    To investigate the underlying mechanisms that control long-term recovery of tundra carbon (C) and nutrients after fire, we employed the Multiple Element Limitation (MEL) model to simulate 200-yr post-fire changes in the biogeochemistry of three sites along a burn severity gradient in response to increases in air temperature, CO 2 concentration, nitrogen (N) deposition, and phosphorus (P) weathering rates. The simulations were conducted for severely burned, moderately burned, and unburned arctic tundra. Our simulations indicated that recovery of C balance after fire was mainly determined by the internal redistribution of nutrients among ecosystem components (controlled by air temperature), rather than the supply of nutrients from external sources (e.g., nitrogen deposition and fixation, phosphorus weathering). Increases in air temperature and atmospheric CO 2 concentration resulted in (1) a net transfer of nutrient from soil organic matter to vegetation and (2) higher C : nutrient ratios in vegetation and soil organic matter. These changes led to gains in vegetation biomass C but net losses in soil organic C stocks. Under a warming climate, nutrients lost in wildfire were difficult to recover because the warming-induced acceleration in nutrient cycles caused further net nutrient loss from the system through leaching. In both burned and unburned tundra, the warming-caused acceleration in nutrient cycles and increases in ecosystem C stocks were eventually constrained by increases in soil C : nutrient ratios, which increased microbial retention of plant-available nutrients in the soil. Accelerated nutrient turnover, loss of C, and increasing soil temperatures will likely result in vegetation changes, which further regulate the long-term biogeochemical succession. Our analysis should help in the assessment of tundra C budgets and of the recovery of biogeochemical function following fire, which is in turn necessary for the maintenance of wildlife habitat and tundra

  17. Nutrient concentrations and loads and Escherichia coli densities in tributaries of the Niantic River estuary, southeastern Connecticut, 2005 and 2008–2011

    Science.gov (United States)

    Mullaney, John R.

    2013-01-01

    Nutrient concentrations and loads and Escherichia coli (E. coli) densities were studied in 2005 and from 2008 through 2011 in water-quality samples from tributaries of the Niantic River Estuary in southeastern Connecticut. Data from a water-quality survey of the base flow of subbasins in the watershed in June 2005 were used to determine the range of total nitrogen concentrations (0.09 to 2.4 milligrams per liter), instantaneous loads (less than 1 to 62 pounds per day) and the yields of total nitrogen ranging from 0.02 to 11.2 pounds per square mile per day (less than 1 to 7.2 kilograms per hectare per year) from basin segments. Nitrogen yields were positively correlated with the amount of developed land in each subbasin. Stable isotope measurements of nitrate (δ15N) and oxygen (δ18O) ranged from 3.9 to 9.4 per mil and 0.7 to 4.1 per mil, respectively, indicating that likely sources of nitrate in base flow are soil nitrate and ammonium fertilizers, sewage or animal waste, or a mixture of these sources. Continuous streamflow and monthly water-quality sampling, with additional storm event sampling, were conducted at the three major tributaries (Latimer Brook, Oil Mill Brook, and Stony Brook) of the Niantic River from October 2008 through September 2011. Samples were analyzed for nitrogen and phosphorus constituents and E. coli densities. Total freshwater discharge from these tributaries, which is reduced by upstream withdrawals, ranged from 25.9 to 37.8 million gallons per day. Total nitrogen and phosphorus concentrations generally were low, with the mean values below the U.S. Environmental Protection Agency recommended nutrient concentration values of 0.71 milligram per liter and 0.031 milligram per liter, respectively. Total nitrogen was predominantly in the form of total ammonia plus organic nitrogen at the Oil Mill Brook and Stony Brook sites and in the form of nitrate at Latimer Brook. Annual total nitrogen loads that flowed into the Niantic River estuary from

  18. Probabilistic model of bridge vehicle loads in port area based on in-situ load testing

    Science.gov (United States)

    Deng, Ming; Wang, Lei; Zhang, Jianren; Wang, Rei; Yan, Yanhong

    2017-11-01

    Vehicle load is an important factor affecting the safety and usability of bridges. An statistical analysis is carried out in this paper to investigate the vehicle load data of Tianjin Haibin highway in Tianjin port of China, which are collected by the Weigh-in- Motion (WIM) system. Following this, the effect of the vehicle load on test bridge is calculated, and then compared with the calculation result according to HL-93(AASHTO LRFD). Results show that the overall vehicle load follows a distribution with a weighted sum of four normal distributions. The maximum vehicle load during the design reference period follows a type I extremum distribution. The vehicle load effect also follows a weighted sum of four normal distributions, and the standard value of the vehicle load is recommended as 1.8 times that of the calculated value according to HL-93.

  19. Modelling the Transfer and Retention of Nutrients in the Drainage Network of the Danube River

    Science.gov (United States)

    Garnier, J.; Billen, G.; Hannon, E.; Fonbonne, S.; Videnina, Y.; Soulie, M.

    2002-03-01

    The Danube catchment basin (817 000 km 2, 76×10 6 inhabitants) is the major freshwater contributor to the Black Sea (6300 m 3 s -1, 80% of the annual river discharge into the north-western Black Sea). The aim of the modelling approach developed for the Danube River, is to establish how land use and management of the whole watershed are linked to nutrient (N, P, Si) delivery and retention by the river. The approach uses an adaptation of the RIVERSTRAHLER model, which is based on a schematic representation of the drainage network deduced from geomorphological analysis by stream orders. The whole catchment was divided into 10 sub-basins and one branch, to provide a description satisfying both the need to take into account the heterogeneity of the system and the availability of constraints and validation data. On the basis of this description, a hydrological model was developed, which adequately simulated the seasonal variations of the discharge measured at the outlet of the basin. The model itself resulted from the coupling of the hydrological model with a biogeochemical model (RIVE), which takes into account the main ecological processes. It established a link between microscopic processes, their controlling factors and their macroscopic manifestations in terms of nutrient cycling and ecological functioning at the scale of the whole drainage network. The model was validated for the period from 1988 to 1991 on the basis of available observations of the major water-quality variables involved in the eutrophication processes (inorganic nutrients, phytoplankton biomass, dissolved oxygen, etc.). A reasonable agreement was found between the simulations of the model and the observations. Nutrient fluxes to the Black Sea, calculated for our reference period, are in the same range as those obtained via other approaches. Si/P and N/P ratios suggest silicon, rather than phosphorus, limitation for diatoms and phosphorus, rather than nitrogen, limitation for overall phytoplankton

  20. Nutrient mitigation in a temporary river basin.

    Science.gov (United States)

    Tzoraki, Ourania; Nikolaidis, Nikolaos P; Cooper, David; Kassotaki, Elissavet

    2014-04-01

    We estimate the nutrient budget in a temporary Mediterranean river basin. We use field monitoring and modelling tools to estimate nutrient sources and transfer in both high and low flow conditions. Inverse modelling by the help of PHREEQC model validated the hypothesis of a losing stream during the dry period. Soil and Water Assessment Tool model captured the water quality of the basin. The 'total daily maximum load' approach is used to estimate the nutrient flux status by flow class, indicating that almost 60% of the river network fails to meet nitrogen criteria and 50% phosphate criteria. We recommend that existing well-documented remediation measures such as reforestation of the riparian area or composting of food process biosolids should be implemented to achieve load reduction in close conjunction with social needs.

  1. Representation of deforestation impacts on climate, water, and nutrient cycles in the ACME earth system model

    Science.gov (United States)

    Cai, X.; Riley, W. J.; Zhu, Q.

    2017-12-01

    Deforestation causes a series of changes to the climate, water, and nutrient cycles. Employing a state-of-the-art earth system model—ACME (Accelerated Climate Modeling for Energy), we comprehensively investigate the impacts of deforestation on these processes. We first assess the performance of the ACME Land Model (ALM) in simulating runoff, evapotranspiration, albedo, and plant productivity at 42 FLUXNET sites. The single column mode of ACME is then used to examine climate effects (temperature cooling/warming) and responses of runoff, evapotranspiration, and nutrient fluxes to deforestation. This approach separates local effects of deforestation from global circulation effects. To better understand the deforestation effects in a global context, we use the coupled (atmosphere, land, and slab ocean) mode of ACME to demonstrate the impacts of deforestation on global climate, water, and nutrient fluxes. Preliminary results showed that the land component of ACME has advantages in simulating these processes and that local deforestation has potentially large impacts on runoff and atmospheric processes.

  2. A Nested Nearshore Nutrient Model (N&Sup3;M) for ...

    Science.gov (United States)

    Nearshore conditions drive phenomena like harmful algal blooms (HABs), and the nearshore and coastal margin are the parts of the Great Lakes most used by humans. To assess conditions, optimize monitoring, and evaluate management options, a model of nearshore nutrient transport and algal dynamics is being developed. The model targets a “regional” spatial scale, similar to the Great Lakes Aquatic Habitat Framework's sub-basins, which divide the nearshore into 30 regions. Model runs are 365 days, a whole season temporal scale, reporting at 3 hour intervals. N³M uses output from existing hydrodynamic models and simple transport kinetics. The nutrient transport component of this model is largely complete, and is being tested with various hydrodynamic data sets. The first test case covers a 200 km² area between two major tributaries to Lake Michigan, the Grand and Muskegon. N³M currently simulates phosphorous and chloride, selected for their distinct in-lake transport dynamics; nitrogen will be added. Initial results for 2003, 2010, and 2015 show encouraging correlations with field measurements. Initially implemented in MatLab, the model is currently implemented in Python and leverages multi-processor computation. The 4D in-browser visualizer Cesium is used to view model output, time varying satellite imagery, and field observations. not applicable

  3. Simulation model of load balancing in distributed computing systems

    Science.gov (United States)

    Botygin, I. A.; Popov, V. N.; Frolov, S. G.

    2017-02-01

    The availability of high-performance computing, high speed data transfer over the network and widespread of software for the design and pre-production in mechanical engineering have led to the fact that at the present time the large industrial enterprises and small engineering companies implement complex computer systems for efficient solutions of production and management tasks. Such computer systems are generally built on the basis of distributed heterogeneous computer systems. The analytical problems solved by such systems are the key models of research, but the system-wide problems of efficient distribution (balancing) of the computational load and accommodation input, intermediate and output databases are no less important. The main tasks of this balancing system are load and condition monitoring of compute nodes, and the selection of a node for transition of the user’s request in accordance with a predetermined algorithm. The load balancing is one of the most used methods of increasing productivity of distributed computing systems through the optimal allocation of tasks between the computer system nodes. Therefore, the development of methods and algorithms for computing optimal scheduling in a distributed system, dynamically changing its infrastructure, is an important task.

  4. Modelling of pressure loads in a pressure suppression pool

    International Nuclear Information System (INIS)

    Timperi, A.; Chauhan, M.; Paettikangas, T.; Niemi, J.

    2013-06-01

    Rapid collapse of a large steam bubble is analyzed by using CFD and FEM calculations. In addition, a 1D code is written which takes into account the finite condensation rate. The 1D simulations are compared with the PPOOLEX experiment COL-01. By adjusting the condensation rate, the calculated pressure peak near the vent outlet could be made same as in the experiment. Scaling of the measured pressure loads to full-scale is studied by dimensional analyses and by review of the analysis of Sonin (1981). The structural response of containment during chugging is studied by using an FEM of containment with simplified geometry and loading which was created based on experimental data. The results are compared to the case in which desynchronization is absent, and chugging occurs simultaneously in every vent pipe. The desynchronized loading is created by giving random initiation times for chugs out of distribution corresponding to the desynchronization time presented by Kukita and Namatame (1985). CFD simulations of the PPOOLEX experiment MIX-03 were performed. In the experiment, clear chugging behavior was observed. In the simulation, the interphasial surface was much more stable and oscillation occurred at a higher frequency than in the experiment. The differences are likely caused by the turbulence model and too coarse numerical mesh, which causes numerical diffusion. (Author)

  5. Modeling of runoff pollution load in a data scarce situation using ...

    African Journals Online (AJOL)

    Sondu watershed is one of the major rivers flowing to Winam Gulf on the Kenyan side of Lake Victoria. The lake is a source of fish and freshwater supply and also provides routes for transportation. Lake deterioration is being driven by excessive pollution load: sediments (TSS) and nutrients (TN & TP). Previous assessments ...

  6. Comprehensive study on parameter sensitivity for flow and nutrient modeling in the Hydrological Simulation Program Fortran model.

    Science.gov (United States)

    Luo, Chuan; Li, Zhaofu; Wu, Min; Jiang, Kaixia; Chen, Xiaomin; Li, Hengpeng

    2017-09-01

    Numerous parameters are used to construct the HSPF (Hydrological Simulation Program Fortran) model, which results in significant difficulty in calibrating the model. Parameter sensitivity analysis is an efficient method to identify important model parameters. Through this method, a model's calibration process can be simplified on the basis of understanding the model's structure. This study investigated the sensitivity of the flow and nutrient parameters of HSPF using the DSA (differential sensitivity analysis) method in the Xitiaoxi watershed, China. The results showed that flow was mostly affected by parameters related to groundwater and evapotranspiration, including DEEPFR (fraction of groundwater inflow to deep recharge), LZETP (lower-zone evapotranspiration parameter), and AGWRC (base groundwater recession), and most of the sensitive parameters had negative and nonlinear effects on flow. Additionally, nutrient components were commonly affected by parameters from land processes, including MON-SQOLIM (monthly values limiting storage of water quality in overland flow), MON-ACCUM (monthly values of accumulation), MON-IFLW-CONC (monthly concentration of water quality in interflow), and MON-GRND-CONC (monthly concentration of water quality in active groundwater). Besides, parameters from river systems, KATM20 (unit oxidation rate of total ammonia at 20 °C) had a negative and almost linear effect on ammonia concentration and MALGR (maximal unit algal growth rate for phytoplankton) had a negative and nonlinear effect on ammonia and orthophosphate concentrations. After calibrating these sensitive parameters, our model performed well for simulating flow and nutrient outputs, with R 2 and E NS (Nash-Sutcliffe efficiency) both greater than 0.75 for flow and greater than 0.5 for nutrient components. This study is expected to serve as a valuable complement to the documentation of the HSPF model to help users identify key parameters and provide a reference for performing

  7. Estimating Demand Response Load Impacts: Evaluation of BaselineLoad Models for Non-Residential Buildings in California

    Energy Technology Data Exchange (ETDEWEB)

    Coughlin, Katie; Piette, Mary Ann; Goldman, Charles; Kiliccote,Sila

    2008-01-01

    Both Federal and California state policymakers areincreasingly interested in developing more standardized and consistentapproaches to estimate and verify the load impacts of demand responseprograms and dynamic pricing tariffs. This study describes a statisticalanalysis of the performance of different models used to calculate thebaseline electric load for commercial buildings participating in ademand-response (DR) program, with emphasis onthe importance of weathereffects. During a DR event, a variety of adjustments may be made tobuilding operation, with the goal of reducing the building peak electricload. In order to determine the actual peak load reduction, an estimateof what the load would have been on the day of the event without any DRactions is needed. This baseline load profile (BLP) is key to accuratelyassessing the load impacts from event-based DR programs and may alsoimpact payment settlements for certain types of DR programs. We testedseven baseline models on a sample of 33 buildings located in California.These models can be loosely categorized into two groups: (1) averagingmethods, which use some linear combination of hourly load values fromprevious days to predict the load on the event, and (2) explicit weathermodels, which use a formula based on local hourly temperature to predictthe load. The models were tested both with and without morningadjustments, which use data from the day of the event to adjust theestimated BLP up or down.Key findings from this study are: - The accuracyof the BLP model currently used by California utilities to estimate loadreductions in several DR programs (i.e., hourly usage in highest 3 out of10 previous days) could be improved substantially if a morning adjustmentfactor were applied for weather-sensitive commercial and institutionalbuildings. - Applying a morning adjustment factor significantly reducesthe bias and improves the accuracy of all BLP models examined in oursample of buildings. - For buildings with low load

  8. Physical and JIT Model Based Hybrid Modeling Approach for Building Thermal Load Prediction

    Science.gov (United States)

    Iino, Yutaka; Murai, Masahiko; Murayama, Dai; Motoyama, Ichiro

    Energy conservation in building fields is one of the key issues in environmental point of view as well as that of industrial, transportation and residential fields. The half of the total energy consumption in a building is occupied by HVAC (Heating, Ventilating and Air Conditioning) systems. In order to realize energy conservation of HVAC system, a thermal load prediction model for building is required. This paper propose a hybrid modeling approach with physical and Just-in-Time (JIT) model for building thermal load prediction. The proposed method has features and benefits such as, (1) it is applicable to the case in which past operation data for load prediction model learning is poor, (2) it has a self checking function, which always supervises if the data driven load prediction and the physical based one are consistent or not, so it can find if something is wrong in load prediction procedure, (3) it has ability to adjust load prediction in real-time against sudden change of model parameters and environmental conditions. The proposed method is evaluated with real operation data of an existing building, and the improvement of load prediction performance is illustrated.

  9. Modeling and Control of a teletruck using electronic load sensing

    DEFF Research Database (Denmark)

    Hansen, Rico Hjerm; Iversen, Asger Malte; Jensen, Mads Schmidt

    2010-01-01

    components and the potential of increased dynamic performance and efficiency, this paper investigates how HLS can be replaced with electronic control, i.e. Electronic Load Sensing (ELS). The investigation is performed by taking a specific application, a teletruck, and replace the HLS control with ELS. To aid...... the controller design for the ELS system, a complete model of the teletruck’s articulated arm and fluid power system is developed. To show the feasibility, a preliminary control structure for the ELS system is developed. The controller is tested on the machine, validating that features such as pump pressure...

  10. A mathematical model for investigating the effect of cluster roots on plant nutrient uptake

    KAUST Repository

    Zygalakis, K. C.

    2012-04-01

    Cluster roots are thought to play an important role in mediating nutrient uptake by plants. In this paper we develop a mathematical model for the transport and uptake of phosphate by a single root. Phosphate is assumed to diffuse in the soil fluid phase and can also solubilised due to citrate exudation. Using multiple scale homogenisation techniques we derive an effective model that accounts for the cumulative effect of citrate exudation and phosphate uptake by cluster roots whilst still retaining all the necessary information about the microscale geometry and effects. © 2012 EDP Sciences and Springer.

  11. Coupling hydrological and impact assessment models to explore nutrient cycling in freshwater systems

    Science.gov (United States)

    Bouwman, Lex; van Beek, Rens; Beusen, Arthur; Mogollón, José; Middelburg, Jack

    2016-04-01

    The IMAGE-Global Nutrient Model (GNM) is a new globally distributed, spatially explicit model in which the hydrology model PCR-GLOBWB is coupled to the integrated assessment model IMAGE to simulate nitrogen (N) and phosphorus (P) delivery, and then with a spiraling ecological approach to simulating instream biogeochemistry. Routing the water with dissolved and suspended N and P from upstream grid cells occurs simultaneous with N and P delivery to water bodies within grid cells from diffuse and point sources (wastewater). IMAGE-GNM describes the following diffuse sources associated with the water flow: surface runoff, shallow and deep groundwater, riparian zones. Depending on the landscape features, all these flows may be present within one grid cell. Furthermore, diffuse N and P inputs occur through allochtonous organic matter inputs via litterfall in (temporarily) inundated river floodplains, and atmospheric deposition. In the spiraling concept, the residence time of the water and nutrient uptake velocity determine N and P retention in water bodies. Validation of model results with observations yields acceptable agreement given the global scale of the uncalibrated model. Sensitivity analysis shows shifts in the importance of the different sources, with decreasing importance of natural sources and increasing influence of wastewater and agriculture. IMAGE-GNM can be employed to study the interaction between society and the environment over prolonged time periods. Here we show results for the full 20th century.

  12. Aggregated Residential Load Modeling Using Dynamic Bayesian Networks

    Energy Technology Data Exchange (ETDEWEB)

    Vlachopoulou, Maria; Chin, George; Fuller, Jason C.; Lu, Shuai

    2014-09-28

    Abstract—It is already obvious that the future power grid will have to address higher demand for power and energy, and to incorporate renewable resources of different energy generation patterns. Demand response (DR) schemes could successfully be used to manage and balance power supply and demand under operating conditions of the future power grid. To achieve that, more advanced tools for DR management of operations and planning are necessary that can estimate the available capacity from DR resources. In this research, a Dynamic Bayesian Network (DBN) is derived, trained, and tested that can model aggregated load of Heating, Ventilation, and Air Conditioning (HVAC) systems. DBNs can provide flexible and powerful tools for both operations and planing, due to their unique analytical capabilities. The DBN model accuracy and flexibility of use is demonstrated by testing the model under different operational scenarios.

  13. Characteristics and modeling of spruce wood under dynamic compression load

    International Nuclear Information System (INIS)

    Eisenacher, Germar

    2014-01-01

    Spruce wood is frequently used as an energy absorbing material in impact limiters of packages for the transportation of radioactive material. A 9m drop test onto an unyielding target is mandatory for the packages. The impact results in a dynamic compression load of the spruce wood inside the impact limiter. The lateral dilation of the wood is restrained thereby due to encasing steel sheets. This work's objective was to provide a material model for spruce wood based on experimental investigations to enable the calculation of such loading conditions. About 600 crush tests with cubical spruce wood specimens were performed to characterize the material. The compression was up to 70% and the material was assumed to be transversely isotropic. Particularly the lateral constraint showed to have an important effect: the material develops a high lateral dilation without lateral constraint. The force-displacement characteristics show a comparably low force level and no or only slight hardening. Distinctive softening occurs after the linear-elastic region when loaded parallel to the fiber. On the other hand, using a lateral constraint results in significantly higher general force levels, distinctive hardening and lateral forces. The softening effect when loaded parallel to the fiber is less distinctive. Strain rate and temperature raise or lower the strength level, which was quantified for the applicable ranges of impact limiters. The hypothesis of an uncoupled evolution of the yield surface was proposed based on the experimental findings. It postulates an independent strength evolution with deviatoric and volumetric deformation. The hypothesis could be established using the first modeling approach, the modified LS-DYNA material model MAT075. A transversely isotropic material model was developed based thereupon and implemented in LS-DYNA. The material characteristics of spruce wood were considered using a multi-surface yield criterion and a non-associated flow rule. The yield

  14. Load modeling for sharp V-cutter cutting litchi ( Litchi chinensis Sonn ...

    African Journals Online (AJOL)

    harvesting. Cutting load is a key parameter for 'hand-held auto-picker' operation. However, there is still no suitable model for cutting load setting. Hence, a model describing the relationship among cutting load, blade angle and friction coefficient was developed for cutting operation by sharp V-cutters. The model was based ...

  15. A freshwater food web model for the combined effects of nutrients and insecticide stress and subsequent recovery

    NARCIS (Netherlands)

    Traas, T.P.; Janse, J.H.; Brink, van den P.J.; Brock, T.C.M.; Aldenberg, T.

    2004-01-01

    A microcosm experiment that addressed the interaction between eutrophication processes and contaminants was analyzed using a food web model. Both direct and indirect effects of nutrient additions and a single insecticide application (chlorpyrifos) on biomass dynamics and recovery of functional

  16. Seasonal variation of nutrient loads in treated wastewater effluents and receiving water bodies in Sedibeng and Soshanguve, South Africa.

    Science.gov (United States)

    Teklehaimanot, G Z; Kamika, I; Coetzee, M A A; Momba, M N B

    2015-09-01

    and between 38.1 and 65.7 for the receiving water bodies. These findings revealed that the receiving water bodies were classified as having "poor" quality status, except Leeuwkuil receiving water body (Vaal River) and Sandspruit upstream (Sandspruit stream). The dry season showed a relatively lower water quality index. This situation might be attributed to the higher amount of organic matter and lower microbial activities in the receiving water bodies. This study suggests that wastewater effluents and receiving water systems should be monitored regularly to ensure best practices with regard to nutrient treatment and discharge of wastewater.

  17. Modeled sensitivity of Lake Michigan productivity and zooplankton to changing nutrient concentrations and quagga mussels

    Science.gov (United States)

    Pilcher, Darren J.; McKinley, Galen A.; Kralj, James; Bootsma, Harvey A.; Reavie, Euan D.

    2017-08-01

    The recent decline in Lake Michigan productivity is often attributed to filter feeding by invasive quagga mussels, but some studies also implicate reductions in lakewide nutrient concentrations. We use a 3-D coupled hydrodynamic-biogeochemical model to evaluate the effect of changing nutrient concentrations and quagga mussel filtering on phytoplankton production and phytoplankton and zooplankton biomass. Sensitivity experiments are used to assess the net effect of each change separately and in unison. Quagga mussels are found to have the greatest impact during periods of isothermal mixing, while nutrients have the greatest impact during thermal stratification. Quagga mussels also act to enhance spatial heterogeneity, particularly between nearshore-offshore regions. This effect produces a reversal in the gradient of nearshore-offshore productivity: from relatively greater nearshore productivity in the prequagga lake to relatively lesser nearshore productivity after quaggas. The combined impact of both processes drives substantial reductions in phytoplankton and zooplankton biomass, as well as significant modifications to the seasonality of surface water pCO2, particularly in nearshore regions where mussel grazing continues year-round. These results support growing concern that considerable losses of phytoplankton and zooplankton will yield concurrent losses at higher trophic levels. Comparisons to observed productivity suggest that both quagga mussel filtration and lower lakewide total phosphorus are necessary to accurately simulate recent changes in primary productivity in Lake Michigan.

  18. Nutrient limitation on terrestrial plant growth--modeling the interaction between nitrogen and phosphorus.

    Science.gov (United States)

    Agren, Göran I; Wetterstedt, J Å Martin; Billberger, Magnus F K

    2012-06-01

    Growth of plants in terrestrial ecosystems is often limited by the availability of nitrogen (N) or phosphorous (P) Liebig's law of the minimum states that the nutrient in least supply relative to the plant's requirement will limit the plant's growth. An alternative to the law of the minimum is the multiple limitation hypothesis (MLH) which states that plants adjust their growth patterns such that they are limited by several resources simultaneously. We use a simple model of plant growth and nutrient uptake to explore the consequences for the plant's relative growth rate of letting plants invest differentially in N and P uptake. We find a smooth transition between limiting elements, in contrast to the strict transition in Liebig's law of the minimum. At N : P supply ratios where the two elements simultaneously limit growth, an increase in either of the nutrients will increase the growth rate because more resources can be allocated towards the limiting element, as suggested by the multiple limitation hypothesis. However, the further the supply ratio deviates from these supply rates, the more the plants will follow the law of the minimum. Liebig's law of the minimum will in many cases be a useful first-order approximation. © 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.

  19. Modeling carbon-nutrient interactions during the early recovery of tundra after fire.

    Science.gov (United States)

    Jiang, Yueyang; Rastetter, Edward B; Rocha, Adrian V; Pearce, Andrea R; Kwiatkowski, Bonnie L; Shaver, Gaius R

    2015-09-01

    Fire frequency has dramatically increased in the tundra of northern Alaska, USA, which has major implications for the carbon budget of the region and the functioning of these ecosystems, which support important wildlife species. We investigated the postfire succession of plant and soil carbon (C), nitrogen (N), and phosphorus (P) fluxes and stocks along a burn severity gradient in the 2007 Anaktuvuk River fire scar in northern Alaska. Modeling results indicated that the early regrowth of postfire tundra vegetation was limited primarily by its canopy photosynthetic potential, rather than nutrient availability, because of the initially low leaf area and relatively high inorganic N and P concentrations in soil. Our simulations indicated that the postfire recovery of tundra vegetation was sustained predominantly by the uptake of residual inorganic N (i.e., in the remaining ash), and the redistribution of N and P from soil organic matter to vegetation. Although residual nutrients in ash were higher in the severe burn than the moderate burn, the moderate burn recovered faster because of the higher remaining biomass and consequent photosynthetic potential. Residual nutrients in ash allowed both burn sites to recover and exceed the unburned site in both aboveground biomass and production five years after the fire. The investigation of interactions among postfire C, N, and P cycles has contributed to a mechanistic understanding of the response of tundra ecosystems to fire disturbance. Our study provided insight on how the trajectory of recovery of tundra from wildfire is regulated during early succession.

  20. Validation of Simplified Load Equations Through Loads Measurement and Modeling of a Small Horizontal-Axis Wind Turbine Tower

    Energy Technology Data Exchange (ETDEWEB)

    Dana, Scott [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Van Dam, Jeroen J [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Damiani, Rick R [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2018-04-24

    As part of an ongoing effort to improve the modeling and prediction of small wind turbine dynamics, the National Renewable Energy Laboratory (NREL) tested a small horizontal-axis wind turbine in the field at the National Wind Technology Center. The test turbine was a 2.1-kW downwind machine mounted on an 18-m multi-section fiberglass composite tower. The tower was instrumented and monitored for approximately 6 months. The collected data were analyzed to assess the turbine and tower loads and further validate the simplified loads equations from the International Electrotechnical Commission (IEC) 61400-2 design standards. Field-measured loads were also compared to the output of an aeroelastic model of the turbine. In particular, we compared fatigue loads as measured in the field, predicted by the aeroelastic model, and calculated using the simplified design equations. Ultimate loads at the tower base were assessed using both the simplified design equations and the aeroelastic model output. The simplified design equations in IEC 61400-2 do not accurately model fatigue loads and a discussion about the simplified design equations is discussed.

  1. Identifying 'unhealthy' food advertising on television: a case study applying the UK Nutrient Profile model.

    Science.gov (United States)

    Jenkin, Gabrielle; Wilson, Nick; Hermanson, Nicole

    2009-05-01

    To evaluate the feasibility of the UK Nutrient Profile (NP) model for identifying 'unhealthy' food advertisements using a case study of New Zealand television advertisements. Four weeks of weekday television from 15.30 hours to 18.30 hours was videotaped from a state-owned (free-to-air) television channel popular with children. Food advertisements were identified and their nutritional information collected in accordance with the requirements of the NP model. Nutrient information was obtained from a variety of sources including food labels, company websites and a national nutritional database. From the 60 h sample of weekday afternoon television, there were 1893 advertisements, of which 483 were for food products or retailers. After applying the NP model, 66 % of these were classified as advertising high-fat, high-salt and high-sugar (HFSS) foods; 28 % were classified as advertising non-HFSS foods; and the remaining 2 % were unclassifiable. More than half (53 %) of the HFSS food advertisements were for 'mixed meal' items promoted by major fast-food franchises. The advertising of non-HFSS food was sparse, covering a narrow range of food groups, with no advertisements for fresh fruit or vegetables. Despite the NP model having some design limitations in classifying real-world televised food advertisements, it was easily applied to this sample and could clearly identify HFSS products. Policy makers who do not wish to completely restrict food advertising to children outright should consider using this NP model for regulating food advertising.

  2. Clustering disaggregated load profiles using a Dirichlet process mixture model

    International Nuclear Information System (INIS)

    Granell, Ramon; Axon, Colin J.; Wallom, David C.H.

    2015-01-01

    Highlights: • We show that the Dirichlet process mixture model is scaleable. • Our model does not require the number of clusters as an input. • Our model creates clusters only by the features of the demand profiles. • We have used both residential and commercial data sets. - Abstract: The increasing availability of substantial quantities of power-use data in both the residential and commercial sectors raises the possibility of mining the data to the advantage of both consumers and network operations. We present a Bayesian non-parametric model to cluster load profiles from households and business premises. Evaluators show that our model performs as well as other popular clustering methods, but unlike most other methods it does not require the number of clusters to be predetermined by the user. We used the so-called ‘Chinese restaurant process’ method to solve the model, making use of the Dirichlet-multinomial distribution. The number of clusters grew logarithmically with the quantity of data, making the technique suitable for scaling to large data sets. We were able to show that the model could distinguish features such as the nationality, household size, and type of dwelling between the cluster memberships

  3. Image-based modelling of nutrient movement in and around the rhizosphere.

    Science.gov (United States)

    Daly, Keith R; Keyes, Samuel D; Masum, Shakil; Roose, Tiina

    2016-02-01

    In this study, we developed a spatially explicit model for nutrient uptake by root hairs based on X-ray computed tomography images of the rhizosphere soil structure. This work extends our previous work to larger domains and hence is valid for longer times. Unlike the model used previously, which considered only a small region of soil about the root, we considered an effectively infinite volume of bulk soil about the rhizosphere. We asked the question: At what distance away from root surfaces do the specific structural features of root-hair and soil aggregate morphology not matter because average properties start dominating the nutrient transport? The resulting model was used to capture bulk and rhizosphere soil properties by considering representative volumes of soil far from the root and adjacent to the root, respectively. By increasing the size of the volumes that we considered, the diffusive impedance of the bulk soil and root uptake were seen to converge. We did this for two different values of water content. We found that the size of region for which the nutrient uptake properties converged to a fixed value was dependent on the water saturation. In the fully saturated case, the region of soil we needed to consider was only of radius 1.1mm for poorly soil-mobile species such as phosphate. However, in the case of a partially saturated medium (relative saturation 0.3), we found that a radius of 1.4mm was necessary. This suggests that, in addition to the geometrical properties of the rhizosphere, there is an additional effect of soil moisture properties, which extends further from the root and may relate to other chemical changes in the rhizosphere. The latter were not explicitly included in our model. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.

  4. Load Model Verification, Validation and Calibration Framework by Statistical Analysis on Field Data

    Science.gov (United States)

    Jiao, Xiangqing; Liao, Yuan; Nguyen, Thai

    2017-11-01

    Accurate load models are critical for power system analysis and operation. A large amount of research work has been done on load modeling. Most of the existing research focuses on developing load models, while little has been done on developing formal load model verification and validation (V&V) methodologies or procedures. Most of the existing load model validation is based on qualitative rather than quantitative analysis. In addition, not all aspects of model V&V problem have been addressed by the existing approaches. To complement the existing methods, this paper proposes a novel load model verification and validation framework that can systematically and more comprehensively examine load model's effectiveness and accuracy. Statistical analysis, instead of visual check, quantifies the load model's accuracy, and provides a confidence level of the developed load model for model users. The analysis results can also be used to calibrate load models. The proposed framework can be used as a guidance to systematically examine load models for utility engineers and researchers. The proposed method is demonstrated through analysis of field measurements collected from a utility system.

  5. Nutrients and Energy Balance Analysis for a Conceptual Model of a Three Loops off Grid, Aquaponics

    Directory of Open Access Journals (Sweden)

    Uri Yogev

    2016-12-01

    Full Text Available Food security, specifically in water scarce regions, is an increasing local and global challenge. Finding new ways to increase agricultural production in a sustainable manner is required. The current study suggests a conceptual model to integrate established recirculating aquaculture practices into a near-zero discharge aquaponic system that efficiently utilizes water, excreted nutrients and organic matter for energy. The suggested model allows to significantly extend the planted area and recover energy in the form of biogas to operate the system off-grid. A mass balance model of nitrogen, carbon and energy was established and solved, based on data from the literature. Results demonstrate that a fish standing stock of about 700 kg would produce 3.4 tons of fish annually and enough nutrients to grow about 35 tons of tomatoes per year (chosen as a model plant and recover sufficient energy (70 kWh/day to run the system on biogas and use less water. If proven successful, this approach may play a major role in sustainably enhancing food security in rural and water scarce regions.

  6. Nutrient trends through time in Sweden's Baltic Drainage Area

    Science.gov (United States)

    Fischer, I.; Destouni, G.; Prieto, C.

    2015-12-01

    Changes in climate and land-use have and will continue to modify regional hydrology, in turn impacting environmental health, agricultural productivity and water resource quality and availability. The Baltic region is an area of interest as the coast spans nine countries- serving over 100 million people. The Baltic Sea contains one of the largest human caused hypoxic dead zones due to eutrophication driven by anthropogenic excess loading of nutrients. Policies to reduce these loads include also international directives and agreements, such as the EU Water Framework Directive, adopted in 2000 to protect and improve water quality throughout the European Union, and the Baltic Sea Action Plan under the Helsinki Commission aimed specifically at reducing the nutrient loading to and mitigating the eutrophication of the Baltic Sea. In light of these policies and amidst the number of studies on the Baltic Sea we ask, using the accessible nutrient and discharge data what does nutrient loading look like today? Are the most excessive loads going down? Observed nutrient and flow time series across Sweden allow for answering these questions, by spatial and temporal trend analysis of loads from various parts of Sweden to the Baltic Sea. Analyzing these observed time series in conjunction with the ecological health status classifications of the EU Water Framework Directive, allows in particular for answering the question if the loads into the water bodies with the poorest water quality, and from those to the Baltic Sea, are improving, being maintained or deteriorating. Such insight is required to contribute to relevant and efficient water and nutrient load management. Furthermore, empirically calculating nutrient loads, rather than only modeling, reveals that the water body health classification may not reflect what water bodies actually contribute the heaviest loads to the Baltic Sea. This work also underscores the importance of comprehensive analysis of all available data from

  7. Mathematical Modeling of Column-Base Connections under Monotonic Loading

    Directory of Open Access Journals (Sweden)

    Gholamreza Abdollahzadeh

    2014-12-01

    Full Text Available Some considerable damage to steel structures during the Hyogo-ken Nanbu Earthquake occurred. Among them, many exposed-type column bases failed in several consistent patterns, such as brittle base plate fracture, excessive bolt elongation, unexpected early bolt failure, and inferior construction work, etc. The lessons from these phenomena led to the need for improved understanding of column base behavior. Joint behavior must be modeled when analyzing semi-rigid frames, which is associated with a mathematical model of the moment–rotation curve. The most accurate model uses continuous nonlinear functions. This article presents three areas of steel joint research: (1 analysis methods of semi-rigid joints; (2 prediction methods for the mechanical behavior of joints; (3 mathematical representations of the moment–rotation curve. In the current study, a new exponential model to depict the moment–rotation relationship of column base connection is proposed. The proposed nonlinear model represents an approach to the prediction of M–θ curves, taking into account the possible failure modes and the deformation characteristics of the connection elements. The new model has three physical parameters, along with two curve-fitted factors. These physical parameters are generated from dimensional details of the connection, as well as the material properties. The M–θ curves obtained by the model are compared with published connection tests and 3D FEM research. The proposed mathematical model adequately comes close to characterizing M–θ behavior through the full range of loading/rotations. As a result, modeling of column base connections using the proposed mathematical model can give crucial beforehand information, and overcome the disadvantages of time consuming workmanship and cost of experimental studies.

  8. Concept mapping One-Carbon Metabolism to model future ontologies for nutrient-gene-phenotype interactions.

    Science.gov (United States)

    Joslin, A C; Green, R; German, J B; Lange, M C

    2014-09-01

    Advances in the development of bioinformatic tools continue to improve investigators' ability to interrogate, organize, and derive knowledge from large amounts of heterogeneous information. These tools often require advanced technical skills not possessed by life scientists. User-friendly, low-barrier-to-entry methods of visualizing nutrigenomics information are yet to be developed. We utilized concept mapping software from the Institute for Human and Machine Cognition to create a conceptual model of diet and health-related data that provides a foundation for future nutrigenomics ontologies describing published nutrient-gene/polymorphism-phenotype data. In this model, maps containing phenotype, nutrient, gene product, and genetic polymorphism interactions are visualized as triples of two concepts linked together by a linking phrase. These triples, or "knowledge propositions," contextualize aggregated data and information into easy-to-read knowledge maps. Maps of these triples enable visualization of genes spanning the One-Carbon Metabolism (OCM) pathway, their sequence variants, and multiple literature-mined associations including concepts relevant to nutrition, phenotypes, and health. The concept map development process documents the incongruity of information derived from pathway databases versus literature resources. This conceptual model highlights the importance of incorporating information about genes in upstream pathways that provide substrates, as well as downstream pathways that utilize products of the pathway under investigation, in this case OCM. Other genes and their polymorphisms, such as TCN2 and FUT2, although not directly involved in OCM, potentially alter OCM pathway functionality. These upstream gene products regulate substrates such as B12. Constellations of polymorphisms affecting the functionality of genes along OCM, together with substrate and cofactor availability, may impact resultant phenotypes. These conceptual maps provide a foundational

  9. Three-dimensional water quality model based on FVCOM for total load control management in Guan River Estuary, Northern Jiangsu Province

    Science.gov (United States)

    Zhang, Li; Lin, Weibo; Li, Keqiang; Sheng, Jianming; Wei, Aihong; Luo, Feng; Wang, Yan; Wang, Xiulin; Zhang, Longjun

    2016-04-01

    Guan River Estuary and adjacent coastal area (GREC) suffer from serious pollution and eutrophicational problems over the recent years. Thus, reducing the land-based load through the national pollutant total load control program and developing hydrodynamic and water quality models that can simulate the complex circulation and water quality kinetics within the system, including longitudinal and lateral variations in nutrient and COD concentrations, is a matter of urgency. In this study, a three-dimensional, hydrodynamic, water quality model was developed in GREC, Northern Jiangsu Province. The complex three-dimensional hydrodynamics of GREC were modeled using the unstructured-grid, finite-volume, free-surface, primitive equation coastal ocean circulation model (FVCOM). The water quality model was adapted from the mesocosm nutrients dynamic model in the south Yellow Sea and considers eight compartments: dissolved inorganic nitrogen, soluble reactive phosphorus (SRP), phytoplankton, zooplankton, detritus, dissolved organic nitrogen (DON), dissolved organic phosphorus (DOP), and chemical oxygen demand. The hydrodynamic and water quality models were calibrated and confirmed for 2012 and 2013. A comparison of the model simulations with extensive dataset shows that the models accurately simulate the longitudinal distribution of the hydrodynamics and water quality. The model can be used for total load control management to improve water quality in this area.

  10. Model-Based Nutrient Feeding Strategies for the Increased Production of Polyhydroxybutyrate (PHB) by Alcaligenes latus.

    Science.gov (United States)

    Gahlawat, Geeta; Srivastava, Ashok K

    2017-10-01

    Polyhydroxyalkanoates (PHAs) are biodegradable polymers which are considered as an effective alternative for conventional plastics due to their mechanical properties similar to the latter. However, the widespread use of these polymers is still hampered due to their higher cost of production as compared to plastics. The production cost could be overcome by obtaining high yields and productivity. The goal of the present research was to enhance the yield of polyhydroxybutyrate (PHB) with the help of two simple fed-batch cultivation strategies. In the present study, average batch kinetic and substrate limitation/inhibition study data of Alcaligenes latus was used for the development of PHB model which was then adopted for designing various off-line nutrient feeding strategies to enhance PHB accumulation. The predictive ability of the model was validated by experimental implementation of two fed-batch strategies. One such dynamic strategy of fed-batch cultivation under pseudo-steady state with respect to nitrogen and simultaneous carbon feeding strategy resulted in significantly high biomass and PHB concentration of 39.17 g/L and 29.64 g/L, respectively. This feeding strategy demonstrated a high PHB productivity and PHB content of 0.6 g/L h and 75%, respectively, which were remarkably high in comparison to batch cultivation. The mathematical model can also be employed for designing various other nutrient feeding strategies.

  11. Low-complexity energy disaggregation using appliance load modelling

    Directory of Open Access Journals (Sweden)

    Hana Altrabalsi

    2016-01-01

    Full Text Available Large-scale smart metering deployments and energy saving targets across the world have ignited renewed interest in residential non-intrusive appliance load monitoring (NALM, that is, disaggregating total household’s energy consumption down to individual appliances, using purely analytical tools. Despite increased research efforts, NALM techniques that can disaggregate power loads at low sampling rates are still not accurate and/or practical enough, requiring substantial customer input and long training periods. In this paper, we address these challenges via a practical low-complexity lowrate NALM, by proposing two approaches based on a combination of the following machine learning techniques: k-means clustering and Support Vector Machine, exploiting their strengths and addressing their individual weaknesses. The first proposed supervised approach is a low-complexity method that requires very short training period and is fairly accurate even in the presence of labelling errors. The second approach relies on a database of appliance signatures that we designed using publicly available datasets. The database compactly represents over 200 appliances using statistical modelling of measured active power. Experimental results on three datasets from US, Italy, Austria and UK, demonstrate the reliability and practicality.

  12. Development of Vehicle Model Test for Road Loading Analysis of Sedan Model

    Science.gov (United States)

    Mohd Nor, M. K.; Noordin, A.; Ruzali, M. F. S.; Hussen, M. H.

    2016-11-01

    Simple Structural Surfaces (SSS) method is offered as a means of organizing the process for rationalizing the basic vehicle body structure load paths. The application of this simplified approach is highly beneficial in the design development of modern passenger car structure especially during the conceptual stage. In Malaysia, however, there is no real physical model of SSS available to gain considerable insight and understanding into the function of each major subassembly in the whole vehicle structures. Based on this motivation, a physical model of SSS for sedan model with the corresponding model vehicle tests of bending and torsion is proposed in this work. The proposed approach is relatively easy to understand as compared to Finite Element Method (FEM). The results show that the proposed vehicle model test is capable to show that satisfactory load paths can give a sufficient structural stiffness within the vehicle structure. It is clearly observed that the global bending stiffness reduce significantly when more panels are removed from a complete SSS model. It is identified that parcel shelf is an important subassembly to sustain bending load. The results also match with the theoretical hypothesis, as the stiffness of the structure in an open section condition is shown weak when subjected to torsion load compared to bending load. The proposed approach can potentially be integrated with FEM to speed up the design process of automotive vehicle.

  13. Preliminary Study of Soil Available Nutrient Simulation Using a Modified WOFOST Model and Time-Series Remote Sensing Observations

    Directory of Open Access Journals (Sweden)

    Zhiqiang Cheng

    2018-01-01

    Full Text Available The approach of using multispectral remote sensing (RS to estimate soil available nutrients (SANs has been recently developed and shows promising results. This method overcomes the limitations of commonly used methods by building a statistical model that connects RS-based crop growth and nutrient content. However, the stability and accuracy of this model require improvement. In this article, we replaced the statistical model by integrating the World Food Studies (WOFOST model and time series of remote sensing (T-RS observations to ensure stability and accuracy. Time series of HJ-1 A/B data was assimilated into the WOFOST model to extrapolate crop growth simulations from a single point to a large area using a specific assimilation method. Because nutrient-limited growth within the growing season is required and the SAN parameters can only be used at the end of the growing season in the original model, the WOFOST model was modified. Notably, the calculation order was changed, and new soil nutrient uptake algorithms were implemented in the model for nutrient-limited growth estimation. Finally, experiments were conducted in the spring maize plots of Hongxing Farm to analyze the effects of nutrient stress on crop growth and the SAN simulation accuracy. The results confirm the differences in crop growth status caused by a lack of soil nutrients. The new approach can take advantage of these differences to provide better SAN estimates. In general, the new approach can overcome the limitations of existing methods and simulate the SAN status with reliable accuracy.

  14. Sand - rubber mixtures submitted to isotropic loading: a minimal model

    Science.gov (United States)

    Platzer, Auriane; Rouhanifar, Salman; Richard, Patrick; Cazacliu, Bogdan; Ibraim, Erdin

    2017-06-01

    The volume of scrap tyres, an undesired urban waste, is increasing rapidly in every country. Mixing sand and rubber particles as a lightweight backfill is one of the possible alternatives to avoid stockpiling them in the environment. This paper presents a minimal model aiming to capture the evolution of the void ratio of sand-rubber mixtures undergoing an isotropic compression loading. It is based on the idea that, submitted to a pressure, the rubber chips deform and partially fill the porous space of the system, leading to a decrease of the void ratio with increasing pressure. Our simple approach is capable of reproducing experimental data for two types of sand (a rounded one and a sub-angular one) and up to mixtures composed of 50% of rubber.

  15. Modeling of dynamically loaded hydrodynamic bearings at low Sommerfeld numbers

    DEFF Research Database (Denmark)

    Thomsen, Kim

    and failure risk of rolling element bearings do, however, grow exponentially with the size. Therefore hydrodynamic bearings can prove to be a competitive alternative to the current practice of rolling element bearings and ultimately help reducing the cost and carbon footprint of renewable energy generation....... The challenging main bearing operation conditions in a wind turbine pose a demanding development task for the design of a hydrodynamic bearing. In general these conditions include operation at low Reynolds numbers with frequent start and stop at high loads as well as difficult operating conditions dictated...... by environment and other wind turbine components. In this work a numerical multiphysics bearing model is developed in order to allow for accurate performance prediction of hydrodynamic bearings subjected to the challenging conditions that exist in modern wind turbines. This requires the coupling of several...

  16. Vortex rope patterns at different load of hydro turbine model

    Directory of Open Access Journals (Sweden)

    Skripkin Sergey

    2017-01-01

    Full Text Available Operation of hydraulic turbines beyond optimal conditions leads to formation of precessing vortex core in a draft tube that generates powerful pressure pulsations in a hydraulic system. In case of resonance it leads to stability decreasing of hydraulic unit and electrical grid on the whole. In present work, such regimes are explored in a conical part of simplified turbine model. Studies are performed at constant flowrate Q = 70 m3/h and varying the runner rotational speed to explore different loads of the hydroturbine unit. The experiments involve pressure measurements, high speed-visualization and velocity measurements by means of laser Doppler anemometer technique. Interesting finding is related with abrupt increasing precession frequency at low swirl parameter of flow near optimal regime.

  17. Submarine groundwater discharge estimation in an urbanized embayment in Hong Kong via short-lived radium isotopes and its implication of nutrient loadings and primary production.

    Science.gov (United States)

    Luo, Xin; Jiao, Jiu Jimmy; Moore, W S; Lee, Chun Ming

    2014-05-15

    (224)Ra and (223)Ra are adopted as tracers to qualify submarine groundwater discharge (SGD) in Tolo Harbor, a highly urbanized embayment in Hong Kong. Based on the sampling data, a two-layered radium mass balance model is used to estimate lateral SGD and bottom SGD. Total SGD is estimated to be 1.2-3.0 cm d(-1), including lateral SGD of 5.7-7.9 cm d(-1) and bottom SGD of 0.3-2.0 cm d(-1). Fresh SGD is estimated to be (2.1-5.5) × 10(5)m(3)d(-1). Nutrient fluxes (mold(-1)) from SGD are estimated to be (3-7.4) × 10(4) (dissolved inorganic nitrogen), (2.4-6.2) × 10(2) (dissolved inorganic phosphate) and (6.5-16) × 10(4) (dissolved silicate). Primary productivity is estimated to be (1.5-15) × 10(6)gCd(-1), 2-53% of which is supported by SGD-induced phosphate fluxes. The study indicates that SGD is a significant source of nutrients to coastal waters and may cause an obvious increase of primary production. These findings must be considered in future coastal ecological management. Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. An electricity price model with consideration to load and gas price effects.

    Science.gov (United States)

    Huang, Min-xiang; Tao, Xiao-hu; Han, Zhen-xiang

    2003-01-01

    Some characteristics of the electricity load and prices are studied, and the relationship between electricity prices and gas (fuel) prices is analyzed in this paper. Because electricity prices are strongly dependent on load and gas prices, the authors constructed a model for electricity prices based on the effects of these two factors; and used the Geometric Mean Reversion Brownian Motion (GMRBM) model to describe the electricity load process, and a Geometric Brownian Motion(GBM) model to describe the gas prices; deduced the price stochastic process model based on the above load model and gas price model. This paper also presents methods for parameters estimation, and proposes some methods to solve the model.

  19. Modelling of nutrient bioaccessibility in almond seeds based on the fracture properties of their cell walls.

    Science.gov (United States)

    Grassby, Terri; Picout, David R; Mandalari, Giuseppina; Faulks, Richard M; Kendall, Cyril W C; Rich, Gillian T; Wickham, Martin S J; Lapsley, Karen; Ellis, Peter R

    2014-12-01

    The cell walls (dietary fibre) of edible plants, which consist of mainly non-starch polysaccharides, play an important role in regulating nutrient bioaccessibility (release) during digestion in the upper gastrointestinal tract. Recent studies have shown that structurally-intact cell walls hinder lipid release from the parenchyma cells of almond seeds. A theoretical model was developed to predict the bioaccessibility of lipid using simple geometry and data on cell dimensions and particle size for calculating the number of ruptured cells in cut almond cubes. Cubes (2 mm) and finely-ground flour of low and high lipid bioaccessibility, respectively, were prepared from almond cotyledons. The model predictions were compared with data from in vitro gastric and duodenal digestion of almond cubes and flour. The model showed that lipid bioaccessibility is highly dependent on particle size and cell diameter. Only a modified version of the model (the Extended Theoretical Model, ETM), in which the cells at the edges and corners were counted once only, was acceptable for the full range of particle sizes. Lipid release values predicted from the ETM were 5.7% for almond cubes and 42% for almond flour. In vitro digestion of cubes and flour showed that lipid released from ruptured cells was available for hydrolysis and resulted in lipid losses of 9.9 and 39.3%, respectively. The ETM shows considerable potential for predicting lipid release in the upper gastrointestinal tract. Further work is warranted to evaluate the efficacy of this model to accurately predict nutrient bioaccessibility in a broad range of edible plants.

  20. Modeling the interaction of light intensity, nutrient concentration and uranium toxicity in Lemna minor

    Energy Technology Data Exchange (ETDEWEB)

    Zimmer, E.; Horemans, N.; Vandenhove, H. [Belgian Nuclear Research Centre SCK-CEN (Belgium); Cedergreen, N. [University of Copenhagen (Denmark); Jager, T. [Vrije Universiteit Amsterdam (Netherlands)

    2014-07-01

    Radioecology aims at assessing the effect of radionuclides and radiation on the environment. Since we cannot test every possible environmental situation in the laboratory, we need modeling approaches to extrapolate the results of toxicity assays to environmentally relevant scenarios. Therefore, it is of crucial importance to understand the effect of relevant environmental factors, such as nutrients, temperature and light on the toxicity of the test. Radionuclides are often found to induce the production of reactive oxygen species (ROS). In plants, an overload of ROS can lead to disturbances of the photosynthetic system. Since the light intensity determines the efficiency of the photo-systems in plants, it can be expected to interact with the effect of radionuclides. The nutrient concentration of the test medium determines the physiological state of the plant, affecting in turn the plant's capability of dealing with stress and hence influences the toxicity of the contaminant. To study the interaction of stressors with environmental conditions, mechanistic effect modeling is promoted widely in ecotoxicology. In principle, the modelling aims at a mechanistic understanding of the different processes causing the stress individually, and integrating them in one framework to study their joint effect and possible interaction. We here present a mechanistic effect model for Lemna minor (common duckweed), which is based on Dynamic Energy Budget (DEB) theory. Models based on DEB have been used widely to study the effects of compounds on animals. Due to its general applicability to all types of organisms, it holds potential to be used for comparison of species and compounds in a broad context. Energy uptake from the environment is modeled explicitly, and metabolic rates are set to depend on temperature in DEB models. Therefore, they can be used to extrapolate effects to a wide range of environmentally relevant scenarios. Until now, the DEB research in ecotoxicology has

  1. A three-dimensional water quality modeling approach for exploring the eutrophication responses to load reduction scenarios in Lake Yilong (China)

    International Nuclear Information System (INIS)

    Zhao, Lei; Li, Yuzhao; Zou, Rui; He, Bin; Zhu, Xiang; Liu, Yong; Wang, Junsong; Zhu, Yongguan

    2013-01-01

    Lake Yilong in Southwestern China has been under serious eutrophication threat during the past decades; however, the lake water remained clear until sudden sharp increase in Chlorophyll a (Chl a) and turbidity in 2009 without apparent change in external loading levels. To investigate the causes as well as examining the underlying mechanism, a three-dimensional hydrodynamic and water quality model was developed, simulating the flow circulation, pollutant fate and transport, and the interactions between nutrients, phytoplankton and macrophytes. The calibrated and validated model was used to conduct three sets of scenarios for understanding the water quality responses to various load reduction intensities and ecological restoration measures. The results showed that (a) even if the nutrient loads is reduced by as much as 77%, the Chl a concentration decreased only by 50%; and (b) aquatic vegetation has strong interaction with phytoplankton, therefore requiring combined watershed and in-lake management for lake restoration. -- Highlights: ► We quantitatively investigated the non-linear lake responses to load reduction. ► The aquatic ecological condition had a great impact on algal blooms. ► Only water quality improvement cannot ensure the aquatic ecology restoration. -- The lake water quality responds to watershed load reduction in a nonlinear way, which requires combined watershed and in-lake management for lake restoration

  2. Data-Driven Residential Load Modeling and Validation in GridLAB-D

    Energy Technology Data Exchange (ETDEWEB)

    Gotseff, Peter; Lundstrom, Blake

    2017-05-11

    Accurately characterizing the impacts of high penetrations of distributed energy resources (DER) on the electric distribution system has driven modeling methods from traditional static snap shots, often representing a critical point in time (e.g., summer peak load), to quasi-static time series (QSTS) simulations capturing all the effects of variable DER, associated controls and hence, impacts on the distribution system over a given time period. Unfortunately, the high time resolution DER source and load data required for model inputs is often scarce or non-existent. This paper presents work performed within the GridLAB-D model environment to synthesize, calibrate, and validate 1-second residential load models based on measured transformer loads and physics-based models suitable for QSTS electric distribution system modeling. The modeling and validation approach taken was to create a typical GridLAB-D model home that, when replicated to represent multiple diverse houses on a single transformer, creates a statistically similar load to a measured load for a given weather input. The model homes are constructed to represent the range of actual homes on an instrumented transformer: square footage, thermal integrity, heating and cooling system definition as well as realistic occupancy schedules. House model calibration and validation was performed using the distribution transformer load data and corresponding weather. The modeled loads were found to be similar to the measured loads for four evaluation metrics: 1) daily average energy, 2) daily average and standard deviation of power, 3) power spectral density, and 4) load shape.

  3. A semi-analytical bearing model considering outer race flexibility for model based bearing load monitoring

    Science.gov (United States)

    Kerst, Stijn; Shyrokau, Barys; Holweg, Edward

    2018-05-01

    This paper proposes a novel semi-analytical bearing model addressing flexibility of the bearing outer race structure. It furthermore presents the application of this model in a bearing load condition monitoring approach. The bearing model is developed as current computational low cost bearing models fail to provide an accurate description of the more and more common flexible size and weight optimized bearing designs due to their assumptions of rigidity. In the proposed bearing model raceway flexibility is described by the use of static deformation shapes. The excitation of the deformation shapes is calculated based on the modelled rolling element loads and a Fourier series based compliance approximation. The resulting model is computational low cost and provides an accurate description of the rolling element loads for flexible outer raceway structures. The latter is validated by a simulation-based comparison study with a well-established bearing simulation software tool. An experimental study finally shows the potential of the proposed model in a bearing load monitoring approach.

  4. Resource competition model predicts zonation and increasing nutrient use efficiency along a wetland salinity gradient

    Science.gov (United States)

    Schoolmaster, Donald; Stagg, Camille L.

    2018-01-01

    A trade-off between competitive ability and stress tolerance has been hypothesized and empirically supported to explain the zonation of species across stress gradients for a number of systems. Since stress often reduces plant productivity, one might expect a pattern of decreasing productivity across the zones of the stress gradient. However, this pattern is often not observed in coastal wetlands that show patterns of zonation along a salinity gradient. To address the potentially complex relationship between stress, zonation, and productivity in coastal wetlands, we developed a model of plant biomass as a function of resource competition and salinity stress. Analysis of the model confirms the conventional wisdom that a trade-off between competitive ability and stress tolerance is a necessary condition for zonation. It also suggests that a negative relationship between salinity and production can be overcome if (1) the supply of the limiting resource increases with greater salinity stress or (2) nutrient use efficiency increases with increasing salinity. We fit the equilibrium solution of the dynamic model to data from Louisiana coastal wetlands to test its ability to explain patterns of production across the landscape gradient and derive predictions that could be tested with independent data. We found support for a number of the model predictions, including patterns of decreasing competitive ability and increasing nutrient use efficiency across a gradient from freshwater to saline wetlands. In addition to providing a quantitative framework to support the mechanistic hypotheses of zonation, these results suggest that this simple model is a useful platform to further build upon, simulate and test mechanistic hypotheses of more complex patterns and phenomena in coastal wetlands.

  5. Reliability-Based Modeling of Moisture and Load-Duration Effects

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Svensson, Staffan

    2005-01-01

    Load duration effects with respect to reduction of load bearing capacity are very important for structural timber. This paper describes how the load duration effects combined with moisture content and variations c an be determined on basis of simulation of realizations of the time varying load...... and moisture processes. Permanent and snow load sand moisture variations are considered and stochastic models are formulated in accordance with the load models in the Danish structural codes. A damage accumulation model based on fracture mechanics that accounts for both load duration and moisture effects....... The probability of failure as function of time is estimated by simulation. Load duration factors, kmod for different moisture conditions (service classes) are estimated on a probabilistic basis....

  6. Competition for nutrients and light: testing advances in resource competition with a natural phytoplankton community.

    Science.gov (United States)

    Burson, Amanda; Stomp, Maayke; Greenwell, Emma; Grosse, Julia; Huisman, Jef

    2018-02-17

    A key challenge in ecology is to understand how nutrients and light affect the biodiversity and community structure of phytoplankton and plant communities. According to resource competition models, ratios of limiting nutrients are major determinants of the species composition. At high nutrient levels, however, species interactions may shift to competition for light, which might make nutrient ratios less relevant. The "nutrient-load hypothesis" merges these two perspectives, by extending the classic model of competition for two nutrients to include competition for light. Here, we test five key predictions of the nutrient-load hypothesis using multispecies competition experiments. A marine phytoplankton community sampled from the North Sea was inoculated in laboratory chemostats provided with different nitrogen (N) and phosphorus (P) loads, to induce either single resource limitation or co-limitation of N, P and light. Four of the five predictions were validated by the experiments. In particular, different resource limitations favored the dominance of different species. Increasing nutrient loads caused changes in phytoplankton species composition, even if the N:P ratio of the nutrient loads remained constant, by shifting the species interactions from competition for nutrients to competition for light. In all treatments, small species became dominant whereas larger species were competitively excluded, supporting the common view that small cell size provides a competitive advantage under resource-limited conditions. Contrary to expectation, all treatments led to coexistence of diatoms, cyanobacteria and green algae, resulting in a higher diversity of species than predicted by theory. Because the coexisting species comprised three phyla with different photosynthetic pigments, we speculate that niche differentiation in the light spectrum might play a role. Our results show that mechanistic resource competition models that integrate nutrient-based and light

  7. Canopy development of a model herbaceous community exposed to elevated atmospheric CO2 and soil nutrients.

    Science.gov (United States)

    Hartz-Rubin, Jennifer S.; DeLucia, Evan H.

    2001-10-01

    To test the prediction that elevated CO2 increases the maximum leaf area index (LAI) through a stimulation of photosynthesis, we exposed model herbaceous communities to two levels of CO2 crossed with two levels of soil fertility. Elevated CO2 stimulated the initial rate of canopy development and increased cumulative LAI integrated over the growth period, but it had no effect on the maximum LAI. In contrast to CO2, increased soil nutrient availability caused a substantial increase in maximum LAI. Elevated CO2 caused a slight increase in leaf area and nitrogen allocated to upper canopy layers and may have stimulated leaf turnover deep in the canopy. Gas exchange measurements of intact communities made near the time of maximum LAI indicated that soil nutrient availability, but not CO2 enrichment, caused a substantial stimulation of net ecosystem carbon exchange. These data do not support our prediction of a higher maximum LAI by elevated CO2 because the initial stimulation of LAI diminished by the end of the growth period. However, early in development, leaf area and carbon assimilation of communities may have been greatly enhanced. These results suggest that the rate of canopy development in annual communities may be accelerated with future increases in atmospheric CO2 but that maximum LAI is set by soil fertility.

  8. Optimal waste load allocation using graph model for conflict resolution.

    Science.gov (United States)

    Saberi, Leila; Niksokhan, Mohammad Hossein

    2017-03-01

    In this paper, a new methodology is proposed for waste load allocation in river systems using the decision support system (DSS) for the graph model for conflict resolution II (GMCRII), multi-criteria decision making (MCDM) analysis and the Multi-Objective Particle Swarm Optimization (MOPSO) algorithm. Minimization of total treatment and penalty costs and minimization of biological oxygen demand violation of standards at the check point are considered as the main objectives of this study. At first, the water quality along the river was simulated using the Streeter-Phelps (S-P) equation coupled with the MOPSO model. Thereby a trade-off curve between the objectives is obtained and a set of non-dominated solutions is selected. In the next step, the best alternative is chosen using MCDM techniques and the GMCRII DSS package and non-cooperative stability definitions. The applicability and efficiency of the methodology are examined in a real-world case study of the Sefidrud River in the northern part of Iran.

  9. Simplified Entropic Model for the Evaluation of Suspended Load Concentration

    Directory of Open Access Journals (Sweden)

    Domenica Mirauda

    2018-03-01

    Full Text Available Suspended sediment concentration is a key aspect in the forecasting of river evolution dynamics, as well as in water quality assessment, evaluation of reservoir impacts, and management of water resources. The estimation of suspended load often relies on empirical models, of which efficiency is limited by their analytic structure or by the need for calibration parameters. The present work deals with a simplified fully-analytical formulation of the so-called entropic model in order to reproduce the vertical distribution of sediment concentration. The simplification consists in the leading order expansion of the generalized spatial coordinate of the entropic velocity profile that, strictly speaking, applies to the near-bed region, but that provides acceptable results also near the free surface. The proposed closed-form solution, which highlights the interplay among channel morphology, stream power, secondary flows, and suspended transport features, allows reducing the needed number of field measurements and, therefore, the time of field activities. Its accuracy and robustness were successfully tested based on the comparison with laboratory data reported in literature.

  10. Evaluation of soil sustainability along the Rio Grande in West Texas: changes in salt loading and organic nutrients due to farming practices

    Science.gov (United States)

    Cox, C. L.; Ganjegunte, G.; Borrok, D. M.; Lougheed, V.; Ma, L.; Jin, L.

    2011-12-01

    thus have higher salt loading, and that Cotton has a higher clay content. The EC values continuously increase from irrigation water to soil waters, suggesting that as water travels through the soil profile it increases in salinity. Consistent with this observation, cation concentrations in soil waters increased with depth. Therefore, the salts within the soils are mobilized during irrigation. 5TE sensors at all three depths in the field showed spikes in EC, and soil moisture during each period of flood irrigation. Data also suggests a lower bulk EC between irrigation periods which might result from a lower soil moisture content which doesn't solublize the salts. The carbonate- and gypsum- rich soils and surface water in the Rio Grande Basin change with intensity and amount of irrigation, addition of fertilizers, and other agricultural practices. Results from this project contribute to our understanding of salt loading and nutrient cycling in the vulnerable area of the Rio Grande Valley in West Texas.

  11. The Okinawan diet: health implications of a low-calorie, nutrient-dense, antioxidant-rich dietary pattern low in glycemic load.

    Science.gov (United States)

    Willcox, D Craig; Willcox, Bradley J; Todoriki, Hidemi; Suzuki, Makoto

    2009-08-01

    Residents of Okinawa, the southernmost prefecture of Japan, are known for their long average life expectancy, high numbers of centenarians, and accompanying low risk of age-associated diseases. Much of the longevity advantage in Okinawa is thought to be related to a healthy lifestyle, particularly the traditional diet, which is low in calories yet nutritionally dense, especially with regard to phytonutrients in the form of antioxidants and flavonoids. Research suggests that diets associated with a reduced risk of chronic diseases are similar to the traditional Okinawan diet, that is, vegetable and fruit heavy (therefore phytonutrient and antioxidant rich) but reduced in meat, refined grains, saturated fat, sugar, salt, and full-fat dairy products. Many of the characteristics of the diet in Okinawa are shared with other healthy dietary patterns, such as the traditional Mediterranean diet or the modern DASH (Dietary Approaches to Stop Hypertension) diet. Features such as the low levels of saturated fat, high antioxidant intake, and low glycemic load in these diets are likely contributing to a decreased risk for cardiovascular disease, some cancers, and other chronic diseases through multiple mechanisms, including reduced oxidative stress. A comparison of the nutrient profiles of the three dietary patterns shows that the traditional Okinawan diet is the lowest in fat intake, particularly in terms of saturated fat, and highest in carbohydrate intake, in keeping with the very high intake of antioxidant-rich yet calorie-poor orange-yellow root vegetables, such as sweet potatoes, and green leafy vegetables. Deeper analyses of the individual components of the Okinawan diet reveal that many of the traditional foods, herbs, or spices consumed on a regular basis could be labeled "functional foods" and, indeed, are currently being explored for their potential health-enhancing properties.

  12. Bacterioplankton Responses to Increased Organic Carbon and Nutrient Loading in a Boreal Estuary-Separate and Interactive Effects on Growth and Respiration.

    Science.gov (United States)

    Soares, Ana R A; Kritzberg, Emma S; Custelcean, Ioana; Berggren, Martin

    2017-12-18

    Increases in the terrestrial export of dissolved organic carbon (C) to rivers may be associated with additional loading of organic nitrogen (N) and phosphorus (P) to the coastal zone. However, little is known about how these resources interact in the regulation of heterotrophic bacterioplankton metabolism in boreal coastal ecosystems. Here, we measured changes in bacterioplankton production (BP) and respiration (BR) in response to full-factorial (C, N, and P) enrichment experiments at two sites within the Öre estuary, northern Sweden. The BR was stimulated by single C additions and further enhanced by combined additions of C and other nutrients. Single addition of N or P had no effect on BR rates. In contrast, BP was primarily limited by P at the site close to the river mouth and did not respond to C or N additions. However, at the site further away from the near the river mouth, BP was slightly stimulated by single additions of C. Possibly, the natural inflow of riverine bioavailable dissolved organic carbon induced local P limitation of BP near the river mouth, which was then exhausted and resulted in C-limited BP further away from the river mouth. We observed positive interactions between all elements on all responses except for BP at the site close to the river mouth, where P showed an independent effect. In light of predicted increases in terrestrial P and C deliveries, we expect future increases in BP and increases of BR of terrestrially delivered C substrates at the Öre estuary and similar areas.

  13. The M-2 ocean tide loading wave in Alaska: vertical and horizontal displacements, modelled and observed

    DEFF Research Database (Denmark)

    Khan, Shfaqat Abbas; Scherneck, H.G.

    2003-01-01

    Crustal deformations caused by surface load due to ocean tides are strongly dependent on the surface load closest to the observing site. In order to correctly model this ocean loading effect near irregular coastal areas, a high-resolution coastline is required. A test is carried out using two GPS...

  14. A Coupled Ocean General Circulation, Biogeochemical, and Radiative Model of the Global Oceans: Seasonal Distributions of Ocean Chlorophyll and Nutrients

    Science.gov (United States)

    Gregg, Watson W.; Busalacchi, Antonio (Technical Monitor)

    2000-01-01

    A coupled ocean general circulation, biogeochemical, and radiative model was constructed to evaluate and understand the nature of seasonal variability of chlorophyll and nutrients in the global oceans. Biogeochemical processes in the model are determined from the influences of circulation and turbulence dynamics, irradiance availability. and the interactions among three functional phytoplankton groups (diatoms. chlorophytes, and picoplankton) and three nutrients (nitrate, ammonium, and silicate). Basin scale (greater than 1000 km) model chlorophyll results are in overall agreement with CZCS pigments in many global regions. Seasonal variability observed in the CZCS is also represented in the model. Synoptic scale (100-1000 km) comparisons of imagery are generally in conformance although occasional departures are apparent. Model nitrate distributions agree with in situ data, including seasonal dynamics, except for the equatorial Atlantic. The overall agreement of the model with satellite and in situ data sources indicates that the model dynamics offer a reasonably realistic simulation of phytoplankton and nutrient dynamics on synoptic scales. This is especially true given that initial conditions are homogenous chlorophyll fields. The success of the model in producing a reasonable representation of chlorophyll and nutrient distributions and seasonal variability in the global oceans is attributed to the application of a generalized, processes-driven approach as opposed to regional parameterization and the existence of multiple phytoplankton groups with different physiological and physical properties. These factors enable the model to simultaneously represent many aspects of the great diversity of physical, biological, chemical, and radiative environments encountered in the global oceans.

  15. Load-Flow in Multiphase Distribution Networks: Existence, Uniqueness, Non-Singularity, and Linear Models

    Energy Technology Data Exchange (ETDEWEB)

    Bernstein, Andrey [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Dall-Anese, Emiliano [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Zhao, Changhong [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Wang, Cong [Ecole Polytechnique Federale de Lausanne (EPFL); Le Boudec, Jean-Yves [Ecole Polytechnique Federale de Lausanne (EPFL)

    2018-04-06

    This paper considers unbalanced multiphase distribution systems with generic topology and different load models, and extends the Z-bus iterative load-flow algorithm based on a fixed-point interpretation of the AC load-flow equations. Explicit conditions for existence and uniqueness of load-flow solutions are presented. These conditions also guarantee convergence of the load-flow algorithm to the unique solution. The proposed methodology is applicable to generic systems featuring (i) wye connections; (ii) ungrounded delta connections; (iii) a combination of wye-connected and delta-connected sources/loads; and, (iv) a combination of line-to-line and line-to-grounded-neutral devices at the secondary of distribution transformers. Further, a sufficient condition for the non-singularity of the load-flow Jacobian is proposed. Finally, linear load-flow models are derived, and their approximation accuracy is analyzed. Theoretical results are corroborated through experiments on IEEE test feeders.

  16. Research Article. Towards a tidal loading model for the Argentine-German Geodetic Observatory (La Plata)

    Science.gov (United States)

    Richter, A.; Müller, L.; Marderwald, E.; Mendoza, L.; Kruse, E.; Perdomo, R.; Scheinert, M.; Perdomo, S.

    2017-02-01

    We present a regionalized model of ocean tidal loading effects for the Argentine-German Geodetic Observatory in La Plata. It provides the amplitudes and phases of gravity variations and vertical deformation for nine tidal constituents to be applied as corrections to the observatory's future geodetic observation data. This model combines a global ocean tide model with a model of the tides in the Río de la Plata estuary. A comparison with conventional predictions based only on the global ocean tide model reveals the importance of the incorporation of the regional tide model. Tidal loading at the observatory is dominated by the tides in the Atlantic Ocean. An additional contribution of local tidal loading in channels and groundwater is examined. The magnitude of the tidal loading is also reviewed in the context of the effects of solid earth tides, atmospheric loading and non-tidal loads.

  17. Alternative wind power modeling methods using chronological and load duration curve production cost models

    Energy Technology Data Exchange (ETDEWEB)

    Milligan, M R

    1996-04-01

    As an intermittent resource, capturing the temporal variation in windpower is an important issue in the context of utility production cost modeling. Many of the production cost models use a method that creates a cumulative probability distribution that is outside the time domain. The purpose of this report is to examine two production cost models that represent the two major model types: chronological and load duration cure models. This report is part of the ongoing research undertaken by the Wind Technology Division of the National Renewable Energy Laboratory in utility modeling and wind system integration.

  18. Improving the Model for Energy Consumption Load Demand Forecasting

    Science.gov (United States)

    Bunnoon, Pituk; Chalermyanont, Kusumal; Limsakul, Chusak

    This paper proposes an application of a filter method in preprocessing stage for mid-term load demand forecasting to improve electricity load forecasting and to guarantee satisfactory forecasting accuracy. Case study employs the historical electricity consumption demand data in Thailand which were recorded in the 12 years of 1997 through to 2007. The load demand forecasted value is used for unit commitment and fuel reserve planning in the power system. This method consists of a trend component and a cyclical component decomposed from the original load demand using the Hodrick-Prescott (HP) filter in the preprocessing stage and the forecasting of each component using Double Neural Networks (DNNs) in the forecasting stage. Experimental results show that with preprocessing before forecasting can predict the load demand better than that without preprocessing.

  19. Benchmarking biological nutrient removal in wastewater treatment plants: influence of mathematical model assumptions.

    Science.gov (United States)

    Flores-Alsina, Xavier; Gernaey, Krist V; Jeppsson, Ulf

    2012-01-01

    This paper examines the effect of different model assumptions when describing biological nutrient removal (BNR) by the activated sludge models (ASM) 1, 2d & 3. The performance of a nitrogen removal (WWTP1) and a combined nitrogen and phosphorus removal (WWTP2) benchmark wastewater treatment plant was compared for a series of model assumptions. Three different model approaches describing BNR are considered. In the reference case, the original model implementations are used to simulate WWTP1 (ASM1 & 3) and WWTP2 (ASM2d). The second set of models includes a reactive settler, which extends the description of the non-reactive TSS sedimentation and transport in the reference case with the full set of ASM processes. Finally, the third set of models is based on including electron acceptor dependency of biomass decay rates for ASM1 (WWTP1) and ASM2d (WWTP2). The results show that incorporation of a reactive settler: (1) increases the hydrolysis of particulates; (2) increases the overall plant's denitrification efficiency by reducing the S(NOx) concentration at the bottom of the clarifier; (3) increases the oxidation of COD compounds; (4) increases X(OHO) and X(ANO) decay; and, finally, (5) increases the growth of X(PAO) and formation of X(PHA,Stor) for ASM2d, which has a major impact on the whole P removal system. Introduction of electron acceptor dependent decay leads to a substantial increase of the concentration of X(ANO), X(OHO) and X(PAO) in the bottom of the clarifier. The paper ends with a critical discussion of the influence of the different model assumptions, and emphasizes the need for a model user to understand the significant differences in simulation results that are obtained when applying different combinations of 'standard' models.

  20. Deformations in the Shoulder Tissues During Load Carriage: A Computational Model.

    Science.gov (United States)

    Hadid, Amir; Belzer, Noa; Shabshin, Nogah; Epstein, Yoram; Gefen, Amit

    2015-11-01

    Shoulder soft tissue deformations seem to be one of the limiting factors of load carriage among soldiers and recreational backpackers that are required to carry heavy loads. Yet, there are no loading limits related to the forces borne by the shoulders, and the backpacks designs are not consistent with providing pressure relief from this sensitive anatomical region. The aim of this study was to develop a model that will enable to study the biomechanical loads that develop in the shoulder under heavy loads and to help in optimizing load carriage systems design. A 3-dimensional, anatomically accurate finite element model of a human shoulder was constructed based on MRI scans. The model was developed to calculate the effective stresses on the skin below the shoulder strap (superficial loads) and the effective strain in the brachial plexus region (inner tissue deformation) for loads of up to 35 kg. The model successfully predicted deformations in the soft tissue surrounding the brachial plexus when compared with deformations measured from load-bearing MRI scans. The model yielded a skin pressure mapping, which showed pressure hotspots in the clavicle region. Inner tissue deformations mapping, as assessed by brachial plexus envelop strains, were found to peak at 30% effective strain at the lateral aspect below the pectoralis muscle. The newly developed model successfully predicted soft tissue deformations in the shoulder related to backpacks. This model can be used to optimize load carriage systems for better distribution of pressure over the shoulders and lower inner tissue deformations.

  1. Nutrient dynamics, transfer and retention along the aquatic continuum from land to ocean: towards integration of ecological and biogeochemical models

    Directory of Open Access Journals (Sweden)

    A. F. Bouwman

    2013-01-01

    Full Text Available In river basins, soils, groundwater, riparian zones and floodplains, streams, rivers, lakes and reservoirs act as successive filters in which the hydrology, ecology and biogeochemical processing are strongly coupled and together act to retain a significant fraction of the nutrients transported. This paper compares existing river ecology concepts with current approaches to describe river biogeochemistry, and assesses the value of these concepts and approaches for understanding the impacts of interacting global change disturbances on river biogeochemistry. Through merging perspectives, concepts, and modeling techniques, we propose integrated model approaches that encompass both aquatic and terrestrial components in heterogeneous landscapes. In this model framework, existing ecological and biogeochemical concepts are extended with a balanced approach for assessing nutrient and sediment delivery, on the one hand, and nutrient in-stream retention on the other hand.

  2. Groundwater-derived nutrient and trace element transport to a nearshore Kona coral ecosystem: Experimental mixing model results

    Directory of Open Access Journals (Sweden)

    Nancy G. Prouty

    2017-06-01

    New Hydrological Insights for the Region: Treated wastewater effluent was the main source for nutrient enrichment downstream at the Honokōhau Harbor site. Conservative mixing for some constituents, such as nitrate + nitrite, illustrate the effectiveness of physical mixing to maintain oceanic concentrations in the colloid (0.02–0.45 μm and truly dissolved (<0.02 μm forms. In contrast, the nonconservative behavior of phosphate highlights the importance of surface complexation reactions that can lead to higher concentrations based on conservative mixing alone. Results from this physiochemical mixing experiment demonstrate how relative availability of P can shift with adsorption behavior, affecting the mobility of phosphate in the environment. With a proposed 8-hectare wastewater treatment facility (WWTF to be constructed upslope of the Kaloko-Honokōhau National Historical Park (NHP, treated effluent is projected to add additional nutrients. Combined with high permeability, rapid discharge, and increased nutrient loading SGD will likely continue to serve as a persistent source of nutrients and potential contaminant to coral ecosystems.

  3. In vitro and in vivo models of Staphylococcus aureus endophthalmitis implicate specific nutrients in ocular infection.

    Directory of Open Access Journals (Sweden)

    Ama Sadaka

    Full Text Available To define global transcriptional responses of Staphylococcus aureus and its codY mutant (CodY is a transcription regulator of virulence and metabolic genes in response to branched-chain amino acids when growing in bovine aqueous (AH and vitreous humor (VH in vitro, and to investigate the impact of codY deletion on S. aureus virulence in a novel murine anterior chamber (AC infection model.For the in vitro model, differential transcriptomic gene expression of S. aureus and its codY mutant grown in chemically defined medium (CDM, AH, and VH was analyzed. Furthermore, the strains were inoculated into the AC of mice. Changes in bacterial growth, electroretinography and inflammation scores were monitored.Bovine AH and VH provide sufficient nutrition for S. aureus growth in vitro. Transcriptome analysis identified 72 unique open reading frames differentially regulated ≥10-fold between CDM, AH, and VH. In the AC model, we found comparable growth of the codY mutant and wild type strains in vivo. Average inflammation scores and retinal function were significantly worse for codY mutant-infected eyes at 24 h post-infection.Our in vitro bovine AH and VH models identified likely nutrient sources for S. aureus in the ocular milieu. The in vivo model suggests that control of branched-chain amino acid availability has therapeutic potential in limiting S. aureus endophthalmitis severity.

  4. Probabilistic model for multi-axial load combinations for wind turbines

    DEFF Research Database (Denmark)

    Dimitrov, Nikolay Krasimirov

    2016-01-01

    The article presents a model describing the joint probability distribution of multiple load components acting on a wind turbine blade cross section. The problem of modelling the probability distribution of load time histories with large periodic components is addressed by dividing the signal...... for determining contemporaneous loads. Using examples with simulated loads on a 10 MW wind turbine,the behavior of the bending moments acting on a blade section is illustrated under different conditions.The loading direction most critical for material failure is determined using a finite-element model...... of the blade cross section on which load combinations with different directions but with equal probability are applied. By defining a joint probability distribution and return-period contours for multiple load components,the suggested procedure is applicable to different aspects of the design of wind turbine...

  5. Does loading influence the severity of cartilage degeneration in the canine groove-model of OA?

    NARCIS (Netherlands)

    Vos, P.; Intema, F.; El, B. van; Groot, J. de; Bijlsma, J.W.J.; Lafeber, F.; Mastbergen, S.

    2009-01-01

    Many animal models are used to study osteoarthritis (OA). In these models the role of joint loading in the development of OA is not fully understood. We studied the effect of loading on the development of OA in the canine Groove-model. In ten female beagle dogs OA was induced in one knee according

  6. The influence of nutrient loading, climate and water depth on nitrogen and phosphorus loss in shallow lakes: a pan-European mesocosm experiment.

    Czech Academy of Sciences Publication Activity Database

    Coppens, J.; Hejzlar, Josef; Šorf, Michal; Jeppesen, E.; Erdogan, S.; Scharfenberger, U.; Mahdy, A.; Noges, P.; Tuvikene, A.; Blaho, D.L.; Trigal, C.; Papastergiadou, E.; Stefanidis, K.; Olsen, S.; Beklioglu, M.

    2016-01-01

    Roč. 778, č. 1 (2016), s. 13-32 ISSN 0018-8158 EU Projects: European Commission(XE) 244121 - REFRESH Institutional support: RVO:60077344 Keywords : nutrient retention * nutrient budget * shallow lake * organic matter * temperature Subject RIV: DA - Hydrology ; Limnology Impact factor: 2.056, year: 2016

  7. Nutrient dynamics and control of eutrophication in the Marne River system: modelling the role of exchangeable phosphorus

    Science.gov (United States)

    Garnier, Josette; Némery, Julien; Billen, Gilles; Théry, Sylvain

    2005-03-01

    The Marne River (12,762 km 2) is one of the main tributaries of the Seine river, upstream from the City of Paris. Its population counts 2 million inhabitants of which 70% are concentrated in the downstream part of the basin. It has a high industrial activity and an intensive agriculture. The Marne River water supplies drinking water production to a large number of Parisians. A diversion reservoir (350×10 6 m 3) is used mainly to sustain summer low flows. On the basis of field observations and experimental studies, a hydrological and ecological model of this river system was built using the Riverstrahler approach (Billen, G., Garnier, J., Hanset, Ph., 1994. Modelling phytoplankton development in whole drainage networks: the riverstrahler model applied to the seine river system. Hydrobiologia 289, 119-137; Garnier, J., Billen, G., Coste, M., 1995. Seasonnal succession of diatoms and Chlorophyceae in the drainage network of the river Seine: observations and modelling. Limnol. Oceanogr. 40, 750-765). The modelling strategy was to consider separately nine sub-basins and the main branch, to which was coupled a model of the reservoir. The point and diffuse sources of nutrients were analysed over more than 10 years (1991-2001) taking into account the role of exchangeable phosphorus (Némery (2003). Origine et devenir du phosphore dans le continuum aquatique de la Seine, des petis basins à l'estuaire. Rôle du phosphore échangeable sur l'eutrophisation. Thèse Univ. Paris 6, p. 258; Némery, J., Garnier, J., Morel, C., 2004. Phosphorus budget in the Marne watershed (France): urban vs. diffuse sources, dissolved vs. particulate forms. Biogeochemistry (in press)). The model was validated through its ability to reproduce available water quality observations. Different realistic scenarios of future reduction of phosphorus load were tested, in various hydrological conditions (dry and wet years). Phytoplankton development can be slightly reduced by a further 85% abatement of

  8. A fuzzy inference model for short-term load forecasting

    International Nuclear Information System (INIS)

    Mamlook, Rustum; Badran, Omar; Abdulhadi, Emad

    2009-01-01

    This paper is concerned with the short-term load forecasting (STLF) in power system operations. It provides load prediction for generation scheduling and unit commitment decisions, and therefore precise load forecasting plays an important role in reducing the generation cost and the spinning reserve capacity. Short-term electricity demand forecasting (i.e., the prediction of hourly loads (demand)) is one of the most important tools by which an electric utility/company plans, dispatches the loading of generating units in order to meet system demand. The accuracy of the dispatching system, which is derived from the accuracy of the forecasting algorithm used, will determine the economics of the operation of the power system. The inaccuracy or large error in the forecast simply means that load matching is not optimized and consequently the generation and transmission systems are not being operated in an efficient manner. In the present study, a proposed methodology has been introduced to decrease the forecasted error and the processing time by using fuzzy logic controller on an hourly base. Therefore, it predicts the effect of different conditional parameters (i.e., weather, time, historical data, and random disturbances) on load forecasting in terms of fuzzy sets during the generation process. These parameters are chosen with respect to their priority and importance. The forecasted values obtained by fuzzy method were compared with the conventionally forecasted ones. The results showed that the STLF of the fuzzy implementation have more accuracy and better outcomes

  9. A servo controlled gradient loading triaxial model test system for deep-buried cavern

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xu-guang [College of Engineering, Ocean University of China, Qingdao 266100 (China); Shandong Provincial Key Laboratory of Ocean Engineering, Qingdao 266100 (China); Research Center of Geotechnical and Structural Engineering, Shandong University, Jinan 250061 (China); Zhang, Qiang-yong; Li, Shu-cai [Research Center of Geotechnical and Structural Engineering, Shandong University, Jinan 250061 (China)

    2015-10-15

    A servo controlled gradient loading model test system is developed to simulate the gradient geostress in deep-buried cavern. This system consists of the gradient loading apparatus, the digital servo control device, and the measurement system. Among them, the gradient loading apparatus is the main component which is used for exerting load onto the model. This loading apparatus is placed inside the counterforce wall/beam and is divided to several different loading zones, with each loading zone independently controlled. This design enables the gradient loading. Hence, the “real” geostress field surrounding the deep-buried cavern can be simulated. The loading or unloading process can be controlled by the human-computer interaction machines, i.e., the digital servo control system. It realizes the automation and visualization of model loading/unloading. In addition, this digital servo could control and regulate hydraulic loading instantaneously, which stabilizes the geostress onto the model over a long term. During the loading procedure, the collision between two adjacent loading platens is also eliminated by developing a guide frame. This collision phenomenon is induced by the volume shrinkage of the model when compressed in true 3D state. In addition, several accurate measurements, including the optical and grating-based method, are adopted to monitor the small deformation of the model. Hence, the distortion of the model could be accurately measured. In order to validate the performance of this innovative model test system, a 3D geomechanical test was conducted on a simulated deep-buried underground reservoir. The result shows that the radial convergence increases rapidly with the release of the stress in the reservoir. Moreover, the deformation increases with the increase of the gas production rate. This observation is consistence with field observation in petroleum engineering. The system is therefore capable of testing deep-buried engineering structures.

  10. A servo controlled gradient loading triaxial model test system for deep-buried cavern

    International Nuclear Information System (INIS)

    Chen, Xu-guang; Zhang, Qiang-yong; Li, Shu-cai

    2015-01-01

    A servo controlled gradient loading model test system is developed to simulate the gradient geostress in deep-buried cavern. This system consists of the gradient loading apparatus, the digital servo control device, and the measurement system. Among them, the gradient loading apparatus is the main component which is used for exerting load onto the model. This loading apparatus is placed inside the counterforce wall/beam and is divided to several different loading zones, with each loading zone independently controlled. This design enables the gradient loading. Hence, the “real” geostress field surrounding the deep-buried cavern can be simulated. The loading or unloading process can be controlled by the human-computer interaction machines, i.e., the digital servo control system. It realizes the automation and visualization of model loading/unloading. In addition, this digital servo could control and regulate hydraulic loading instantaneously, which stabilizes the geostress onto the model over a long term. During the loading procedure, the collision between two adjacent loading platens is also eliminated by developing a guide frame. This collision phenomenon is induced by the volume shrinkage of the model when compressed in true 3D state. In addition, several accurate measurements, including the optical and grating-based method, are adopted to monitor the small deformation of the model. Hence, the distortion of the model could be accurately measured. In order to validate the performance of this innovative model test system, a 3D geomechanical test was conducted on a simulated deep-buried underground reservoir. The result shows that the radial convergence increases rapidly with the release of the stress in the reservoir. Moreover, the deformation increases with the increase of the gas production rate. This observation is consistence with field observation in petroleum engineering. The system is therefore capable of testing deep-buried engineering structures

  11. Nutrient modeling for a semi-intensive IMC pond: an MS-Excel approach.

    Science.gov (United States)

    Ray, Lala I P; Mal, B C; Moulick, S

    2017-11-01

    Semi-intensive Indian Major Carp (IMC) culture was practised in polythene lined dugout ponds at the Aquacultural Farm of Indian Institute of Technology, Kharagpur, West Bengal for 3 consecutive years at three different stocking densities (S.D), viz., 20,000, 35,000 and 50,000 numbers of fingerlings per hectare of water spread area. Fingerlings of Catla, Rohu and Mrigal were raised at a stocking ratio of 4:3:3. Total ammonia nitrogen (TAN) value along with other fishpond water quality parameters was monitored at 1 day intervals to ensure a good water ecosystem for a better fish growth. Water exchange was carried out before the TAN reached the critical limit. Field data on TAN obtained from the cultured fishponds stocked with three different stocking densities were used to study the dynamics of TAN. A developed model used to study the nutrient dynamics in shrimp pond was used to validate the observed data in the IMC pond ecosystem. Two years of observed TAN data were used to calibrate the spreadsheet model and the same model was validated using the third year observed data. The manual calibration based on the trial and error process of parameters adjustments was used and several simulations were performed by changing the model parameters. After adjustment of each parameter, the simulated and measured values of the water quality parameters were compared to judge the improvement in the model prediction. Forward finite difference discretization method was used in a MS-Excel spreadsheet to calibrate and validate the model for obtaining the TAN levels during the culture period. Observed data from the cultured fishponds of three different S.D were used to standardize 13 model parameters. The efficiency of the developed spreadsheet model was found to be more than 90% for the TAN estimation in the IMC cultured fishponds.

  12. Load and Flexibility Models for Distribution Grid Management

    DEFF Research Database (Denmark)

    Kouzelis, Konstantinos

    Recent trends in power systems have favored the electrification of residential heating and transportation by means of modern partially flexible loads. Furthermore, environmental concerns have promoted the notion of distributed generation, thus increasing its penetration in low voltage distribution...... changing the energy flow in low voltage distribution grids, several grid complications are bound to emerge like, for instance, capacity adequacy limitations, power quality issues, reverse power flows etc. One of the Distribution System Operator options to manage these complications is to proceed...... involve lack of generic load forecasts, need for flexible load/generation estimation techniques from smart meter measurements, deficiencies in online load distribution observability, and, finally, energy market compatible control algorithms which treat consumer flexibility in a fair manner. These modules...

  13. Model-based Diagnostics for Propellant Loading Systems

    Data.gov (United States)

    National Aeronautics and Space Administration — The loading of spacecraft propellants is a complex, risky operation. Therefore, diagnostic solutions are neces- sary to quickly identify when a fault occurs, so that...

  14. Short-Term City Electric Load Forecasting with Considering Temperature Effects: An Improved ARIMAX Model

    Directory of Open Access Journals (Sweden)

    Herui Cui

    2015-01-01

    Full Text Available Short-term electric load is significantly affected by weather, especially the temperature effects in summer. External factors can result in mutation structures in load data. Under the influence of the external temperature factors, city electric load cannot be easily forecasted as usual. This research analyzes the relationship between electricity load and daily temperature in city. An improved ARIMAX model is proposed in this paper to deal with the mutation data structures. It is found that information amount of the improved ARIMAX model is smaller than that of the classic method and its relative error is less than AR, ARMA and Sigmoid-Function ANN models. The forecasting results are more accurately fitted. This improved model is highly valuable when dealing with mutation data structure in the field of load forecasting. And it is also an effective technique in forecasting electric load with temperature effects.

  15. Model-Based Load Estimation for Predictive Condition Monitoring of Wind Turbines

    DEFF Research Database (Denmark)

    Perisic, Nevena; Pederen, Bo Juul; Grunnet, Jacob Deleuran

    The main objective of this paper is to present a Load Observer Tool (LOT) for condition monitoring of structural extreme and fatigue loads on the main wind turbine (WTG) components. LOT uses well-known methods from system identification, state estimation and fatigue analysis in a novel approach...... for application in condition monitoring. Fatigue loads are estimated online using a load observer and grey box models which include relevant WTG dynamics. Identification of model parameters and calibration of observer are performed offline using measurements from WTG prototype. Signal processing of estimated load...... signal is performed online, and a Load Indicator Signal (LIS) is formulated as a ratio between current estimated accumulated fatigue loads and its expected value based only on a priori knowledge (WTG dynamics and wind climate). LOT initialisation is based on a priori knowledge and can be obtained using...

  16. An Integrated Modeling and Experimental Approach to Study the Influence of Environmental Nutrients on Biofilm Formation of Pseudomonas aeruginosa.

    Science.gov (United States)

    Xu, Zhaobin; Islam, Sabina; Wood, Thomas K; Huang, Zuyi

    2015-01-01

    The availability of nutrient components in the environment was identified as a critical regulator of virulence and biofilm formation in Pseudomonas aeruginosa. This work proposes the first systems-biology approach to quantify microbial biofilm formation upon the change of nutrient availability in the environment. Specifically, the change of fluxes of metabolic reactions that were positively associated with P. aeruginosa biofilm formation was used to monitor the trend for P. aeruginosa to form a biofilm. The uptake rates of nutrient components were changed according to the change of the nutrient availability. We found that adding each of the eleven amino acids (Arg, Tyr, Phe, His, Iso, Orn, Pro, Glu, Leu, Val, and Asp) to minimal medium promoted P. aeruginosa biofilm formation. Both modeling and experimental approaches were further developed to quantify P. aeruginosa biofilm formation for four different availability levels for each of the three ions that include ferrous ions, sulfate, and phosphate. The developed modeling approach correctly predicted the amount of biofilm formation. By comparing reaction flux change upon the change of nutrient concentrations, metabolic reactions used by P. aeruginosa to regulate its biofilm formation are mainly involved in arginine metabolism, glutamate production, magnesium transport, acetate metabolism, and the TCA cycle.

  17. An Integrated Modeling and Experimental Approach to Study the Influence of Environmental Nutrients on Biofilm Formation of Pseudomonas aeruginosa

    Science.gov (United States)

    Xu, Zhaobin; Islam, Sabina; Wood, Thomas K.; Huang, Zuyi

    2015-01-01

    The availability of nutrient components in the environment was identified as a critical regulator of virulence and biofilm formation in Pseudomonas aeruginosa. This work proposes the first systems-biology approach to quantify microbial biofilm formation upon the change of nutrient availability in the environment. Specifically, the change of fluxes of metabolic reactions that were positively associated with P. aeruginosa biofilm formation was used to monitor the trend for P. aeruginosa to form a biofilm. The uptake rates of nutrient components were changed according to the change of the nutrient availability. We found that adding each of the eleven amino acids (Arg, Tyr, Phe, His, Iso, Orn, Pro, Glu, Leu, Val, and Asp) to minimal medium promoted P. aeruginosa biofilm formation. Both modeling and experimental approaches were further developed to quantify P. aeruginosa biofilm formation for four different availability levels for each of the three ions that include ferrous ions, sulfate, and phosphate. The developed modeling approach correctly predicted the amount of biofilm formation. By comparing reaction flux change upon the change of nutrient concentrations, metabolic reactions used by P. aeruginosa to regulate its biofilm formation are mainly involved in arginine metabolism, glutamate production, magnesium transport, acetate metabolism, and the TCA cycle. PMID:25954752

  18. Support Vector Regression Model Based on Empirical Mode Decomposition and Auto Regression for Electric Load Forecasting

    Directory of Open Access Journals (Sweden)

    Hong-Juan Li

    2013-04-01

    Full Text Available Electric load forecasting is an important issue for a power utility, associated with the management of daily operations such as energy transfer scheduling, unit commitment, and load dispatch. Inspired by strong non-linear learning capability of support vector regression (SVR, this paper presents a SVR model hybridized with the empirical mode decomposition (EMD method and auto regression (AR for electric load forecasting. The electric load data of the New South Wales (Australia market are employed for comparing the forecasting performances of different forecasting models. The results confirm the validity of the idea that the proposed model can simultaneously provide forecasting with good accuracy and interpretability.

  19. Mathematical modelling of nutrient balance of a goldfish (Carassius auratus Linn. recirculating aquaculture system (GRAS

    Directory of Open Access Journals (Sweden)

    Sudeep Puthravilakom Sadasivan Nair

    2010-08-01

    Full Text Available In the present study, a goldfish (Carassius auratus Linn. recirculating aquaculture system (GRAS has been developed. The GRAS consisted of a culture tank, a screen filter and a foam fractionator for removal of particulate and dissolved solids and a trickling filter for conversion of ammonium- and nitrite-nitrogen to relatively harmless nitrate-nitrogen. The culture of goldfish at a stocking density of 1.08 kg/m3 was continued for a period of two and half months. Based on mass balance analysis of ammonium- and nitrate-nitrogen and assuming the trickling filter to be a plug flow reactor, a model was formulated to determine the necessary recirculation flow rate at different times of culture for maintaining the major nutrients, viz., ammonium- and nitrate-nitrogen below their permissible limits. The model was calibrated and validated using the real time data obtained from the experimental run. The high values of coefficient of determination and low values of root mean square error show the effectiveness of the model.

  20. Parametric model to estimate containment loads following an ex-vessel steam spike

    International Nuclear Information System (INIS)

    Lopez, R.; Hernandez, J.; Huerta, A.

    1998-01-01

    This paper describes the use of a relatively simple parametric model to estimate containment loads following an ex-vessel steam spike. The study was motivated because several PSAs have identified containment loads accompanying reactor vessel failures as a major contributor to early containment failure. The paper includes a detailed description of the simple but physically sound parametric model which was adopted to estimate containment loads following a steam spike into the reactor cavity. (author)

  1. Modeling the soil nutrient balance of integrated agriculture-aquaculture systems in the Mekong Delta, Vietnam

    NARCIS (Netherlands)

    Phong, L.T.; Stoorvogel, J.J.; Mensvoort, van M.E.F.; Udo, H.M.J.

    2011-01-01

    This study quantifies soil nutrient balances of Integrated Agriculture-Aquaculture Systems in the Mekong Delta of Vietnam. Eleven farms were monitored to collect data on farm activities and nutrient inputs and outputs to compute these balances of the rice-based and high input fish system in O Mon

  2. A simplified model of dynamic interior cooling load evaluation for office buildings

    International Nuclear Information System (INIS)

    Ding, Yan; Zhang, Qiang; Wang, Zhaoxia; Liu, Min; He, Qing

    2016-01-01

    Highlights: • The core interior disturbance was determined by principle component analysis. • Influences of occupants on cooling load should be described using time series. • A simplified model was built to evaluate dynamic interior building cooling load. - Abstract: Predicted cooling load is a valuable tool for assessing the operation of air-conditioning systems. Compared with exterior cooling load, interior cooling load is more unpredictable. According to principle components analysis, occupancy was proved to be a typical factor influencing interior cooling loads in buildings. By exploring the regularity of interior disturbances in an office building, a simplified evaluation model for interior cooling load was established in this paper. The stochastic occupancy rate was represented by a Markov transition model. Equipment power, lighting power and fresh air were all related to occupancy rate based on time sequence. The superposition of different types of interior cooling loads was also considered in the evaluation model. The error between the evaluation results and measurement results was found to be lower than 10%. In reference to the cooling loads calculated by the traditional design method and area-based method in case study office rooms, the evaluated cooling loads were suitable for operation regulation.

  3. How much certainty is enough? Validation of a nutrient retention model for prioritizing watershed conservation in North Carolina

    Science.gov (United States)

    Hamel, P.; Chaplin-Kramer, R.; Benner, R.

    2013-12-01

    Context Quantifying ecosystems services, nature's benefits to people, is an area of active research in water resource management. Increasingly, water utilities and basin management authorities are interested in optimizing watershed scale conservation strategies to mitigate the economic and environmental impacts of land-use and hydrological changes. While many models are available to represent hydrological processes in a spatially explicit way, large uncertainties remain associated with i) the biophysical outputs of these models (e.g., nutrient concentration at a given location), and ii) the service valuation method to support specific decisions (e.g., targeting conservation areas based on their contribution to retaining nutrient). Better understanding these uncertainties and their impact on the decision process is critical for establishing credibility of such models in a planning context. Methods To address this issue in an emerging payments for watershed services program in the Cape Fear watershed, North Carolina, USA, we tested and validated the use of a nutrient retention model (InVEST) for targeting conservation activities. Specifically, we modeled water yield and nutrient transport throughout the watershed and valued the retention service provided by forested areas. Observed flow and water quality data at multiple locations allowed calibration of the model at the watershed level as well as the subwatershed level. By comparing the results from each model parameterization, we were able to assess the uncertainties related to both the model structure and parameter estimation. Finally, we assessed the use of the model for climate scenario simulation by characterizing its ability to represent inter-annual variability. Results and discussion The spatial analyses showed that the two calibration approaches could yield distinct parameter sets, both for the water yield and the nutrient model. These results imply a difference in the absolute nutrient concentration

  4. Identification of spatiotemporal nutrient patterns in a coastal bay via an integrated k-means clustering and gravity model.

    Science.gov (United States)

    Chang, Ni-Bin; Wimberly, Brent; Xuan, Zhemin

    2012-03-01

    This study presents an integrated k-means clustering and gravity model (IKCGM) for investigating the spatiotemporal patterns of nutrient and associated dissolved oxygen levels in Tampa Bay, Florida. By using a k-means clustering analysis to first partition the nutrient data into a user-specified number of subsets, it is possible to discover the spatiotemporal patterns of nutrient distribution in the bay and capture the inherent linkages of hydrodynamic and biogeochemical features. Such patterns may then be combined with a gravity model to link the nutrient source contribution from each coastal watershed to the generated clusters in the bay to aid in the source proportion analysis for environmental management. The clustering analysis was carried out based on 1 year (2008) water quality data composed of 55 sample stations throughout Tampa Bay collected by the Environmental Protection Commission of Hillsborough County. In addition, hydrological and river water quality data of the same year were acquired from the United States Geological Survey's National Water Information System to support the gravity modeling analysis. The results show that the k-means model with 8 clusters is the optimal choice, in which cluster 2 at Lower Tampa Bay had the minimum values of total nitrogen (TN) concentrations, chlorophyll a (Chl-a) concentrations, and ocean color values in every season as well as the minimum concentration of total phosphorus (TP) in three consecutive seasons in 2008. The datasets indicate that Lower Tampa Bay is an area with limited nutrient input throughout the year. Cluster 5, located in Middle Tampa Bay, displayed elevated TN concentrations, ocean color values, and Chl-a concentrations, suggesting that high values of colored dissolved organic matter are linked with some nutrient sources. The data presented by the gravity modeling analysis indicate that the Alafia River Basin is the major contributor of nutrients in terms of both TP and TN values in all seasons

  5. The relationships between internal and external training load models during basketball training.

    Science.gov (United States)

    Scanlan, Aaron T; Wen, Neal; Tucker, Patrick S; Dalbo, Vincent J

    2014-09-01

    The present investigation described and compared the internal and external training loads during basketball training. Eight semiprofessional male basketball players (mean ± SD, age: 26.3 ± 6.7 years; stature: 188.1 ± 6.2 cm; body mass: 92.0 ± 13.8 kg) were monitored across a 7-week period during the preparatory phase of the annual training plan. A total of 44 total sessions were monitored. Player session ratings of perceived exertion (sRPE), heart rate, and accelerometer data were collected across each training session. Internal training load was determined using the sRPE, training impulse (TRIMP), and summated-heart-rate-zones (SHRZ) training load models. External training load was calculated using an established accelerometer algorithm. Pearson product-moment correlations with 95% confidence intervals (CIs) were used to determine the relationships between internal and external training load models. Significant moderate relationships were observed between external training load and the sRPE (r42 = 0.49, 95% CI = 0.23-0.69, p training load and the SHRZ model (r42 = 0.61, 95% CI = 0.38-0.77, p training load models, the magnitude of the correlations and low commonality suggest that internal training load models measure different constructs of the training process than the accelerometer training load model in basketball settings. Basketball coaching and conditioning professionals should not assume a linear dose-response between accelerometer and internal training load models during training and are recommended to combine internal and external approaches when monitoring training load in players.

  6. Sources of nitrogen and phosphorus emissions to Irish rivers: estimates from the Source Load Apportionment Model (SLAM)

    Science.gov (United States)

    Mockler, Eva; Deakin, Jenny; Archbold, Marie; Daly, Donal; Bruen, Michael

    2017-04-01

    More than half of the river and lake water bodies in Europe are at less than good ecological status or potential, and diffuse pollution from agriculture remains a major, but not the only, cause of this poor performance. In Ireland, it is evident that agri-environmental policy and land management practices have, in many areas, reduced nutrient emissions to water, mitigating the potential impact on water quality. However, additional measures may be required in order to further decouple the relationship between agricultural productivity and emissions to water, which is of vital importance given the on-going agricultural intensification in Ireland. Catchment management can be greatly supported by modelling, which can reduce the resources required to analyse large amounts of information and can enable investigations and measures to be targeted. The Source Load Apportionment Model (SLAM) framework was developed to support catchment management in Ireland by characterising the contributions from various sources of phosphorus (P) and nitrogen (N) emissions to water. The SLAM integrates multiple national spatial datasets relating to nutrient emissions to surface water, including land use and physical characteristics of the sub-catchments to predict emissions from point (wastewater, industry discharges and septic tank systems) and diffuse sources (agriculture, forestry, peatlands, etc.). The annual nutrient emissions predicted by the SLAM were assessed against nutrient monitoring data for 16 major river catchments covering 50% of the area of Ireland. At national scale, results indicate that the total average annual emissions to surface water in Ireland are over 2,700 t yr-1 of P and 80,000 t yr-1 of N. The SLAM results include the proportional contributions from individual sources at a range of scales from sub-catchment to national, and show that the main sources of P are from wastewater and agriculture, with wide variations across the country related to local anthropogenic

  7. Low Load Model of a Once-through Boiler with Recirculation

    DEFF Research Database (Denmark)

    Trangbæk, Klaus

    2006-01-01

    A dynamic simulation model of a once-through boiler in low to medium load is developed. When the system is in low load, water from the evaporator is recirculated through a bottle. This recirculation system is included in the model, which is then shown to fit closed-loop data from a real plant...

  8. Physical Modelling of Bucket Foundation Under Long-Term Cyclic Lateral Loading

    DEFF Research Database (Denmark)

    Foglia, Aligi; Ibsen, Lars Bo; Andersen, Lars Vabbersgaard

    2012-01-01

    functioning. In this article a 1g physical model of bucket foundation under horizontal and moment cyclic loading is described. A testing program including four tests was carried out. Every test was conducted for at least 30000 cycles, each with different loading features. The capability of the model...

  9. Modeling of the stress-strain relationship for specimens made of S355J0 steel subjected to bending block loading with mean load

    Directory of Open Access Journals (Sweden)

    R. Pawliczek

    2017-10-01

    Full Text Available The paper presents results of calculation for modelling of the stressstrain relationship in the case of block loads with mean load value. A model, based on the stable hysteresis loops, was assumed and modified to use for block loading analysis. For stress history calculation, the proposed model and two other constitutive models were used. Results of fatigue test of specimens made of S355J0 steel subjected to bending block loading with mean load value are presented and used to verify the proposed model. In the tests, the mean load was increased and decreased in subsequent blocks. The changes of strain recorded during the tests shown in the paper indicate a different behavior of the material. Damage accumulation degree for block sequence was used to compare the results of calculations. It was shown, that stress history parameters (stress amplitude and mean stress value in this case are similar for all investigated models

  10. Modeling of damage evaluation in thin composite plate loaded by pressure loading

    Directory of Open Access Journals (Sweden)

    Dudinský M.

    2012-12-01

    Full Text Available This article presents the results of numerical analysis of elastic damage of thin laminated long fiber-reinforced composite plate consisting of unidirectional layers which is loaded by uniformly distributed pressure. The analysis has been performed by means of the finite element method (FEM. The numerical implementation uses layered plate finite elements based on the Kirchhoff plate theory. System of nonlinear equations has been solved by means of the Newton- Raphson procedure. Evolution of damage has been solved using the return-mapping algorithm based on the continuum damage mechanics (CDM. The analysis was performed using own program created in MATLAB. Problem of laminated fiber-reinforced composite plate fixed on edges for two different materials and three different laminate stacking sequences (LSS was simulated. Evolution of stresses vs. strains and also evolution of damage variables in critical points of the structure are shown.

  11. ThinTool: a spreadsheet model to evaluate fuel reduction thinning cost, net energy output, and nutrient impacts

    Science.gov (United States)

    Sang-Kyun Han; Han-Sup Han; William J. Elliot; Edward M. Bilek

    2017-01-01

    We developed a spreadsheet-based model, named ThinTool, to evaluate the cost of mechanical fuel reduction thinning including biomass removal, to predict net energy output, and to assess nutrient impacts from thinning treatments in northern California and southern Oregon. A combination of literature reviews, field-based studies, and contractor surveys was used to...

  12. Evaluation of the 'Fertigation Model', a decision support system for water and nutrient supply for soil grown greenhouse crops

    NARCIS (Netherlands)

    Voogt, W.; Winkel, van A.; Steinbuch, F.

    2006-01-01

    Soil grown greenhouse crops require high fertilisation rates. Combined with the common practice of over-irrigation, leaching of nutrients is a serious problem. In order to reduce the environmental impact, a `fertigation¿ model was developed as a decision support system for irrigation and fertiliser

  13. Modeling nitrate-nitrogen load reduction strategies for the Des Moines River, Iowa using SWAT.

    Science.gov (United States)

    Schilling, Keith E; Wolter, Calvin F

    2009-10-01

    The Des Moines River that drains a watershed of 16,175 km(2) in portions of Iowa and Minnesota is impaired for nitrate-nitrogen (nitrate) due to concentrations that exceed regulatory limits for public water supplies. The Soil Water Assessment Tool (SWAT) model was used to model streamflow and nitrate loads and evaluate a suite of basin-wide changes and targeting configurations to potentially reduce nitrate loads in the river. The SWAT model comprised 173 subbasins and 2,516 hydrologic response units and included point and nonpoint nitrogen sources. The model was calibrated for an 11-year period and three basin-wide and four targeting strategies were evaluated. Results indicated that nonpoint sources accounted for 95% of the total nitrate export. Reduction in fertilizer applications from 170 to 50 kg/ha achieved the 38% reduction in nitrate loads, exceeding the 34% reduction required. In terms of targeting, the most efficient load reductions occurred when fertilizer applications were reduced in subbasins nearest the watershed outlet. The greatest load reduction for the area of land treated was associated with reducing loads from 55 subbasins with the highest nitrate loads, achieving a 14% reduction in nitrate loads achieved by reducing applications on 30% of the land area. SWAT model results provide much needed guidance on how to begin implementing load reduction strategies most efficiently in the Des Moines River watershed.

  14. Nutrient Dynamics of the Delta: Effects on Primary Producers

    Directory of Open Access Journals (Sweden)

    Clifford N. Dahm

    2016-12-01

    Full Text Available doi: https://doi.org/10.15447/sfews.2016v14iss4art4Increasing clarity of Delta waters, the emergence of harmful algal blooms, the proliferation of aquatic water weeds, and the altered food web of the Delta have brought nutrient dynamics to the forefront. This paper focuses on the sources of nutrients, the transformation and uptake of nutrients, and the links of nutrients to primary producers. The largest loads of nutrients to the Delta come from the Sacramento River with the San Joaquin River seasonally important, especially in the summer. Nutrient concentrations reflect riverine inputs in winter and internal biological processes during periods of lower flow with internal nitrogen losses within the Delta estimated at approximately 30% annually. Light regime, grazing pressure, and nutrient availability influence rates of primary production at different times and locations within the Delta. The roles of the chemical form of dissolved inorganic nitrogen in growth rates of primary producers in the Delta and the structure of the open-water algal community are currently topics of much interest and considerable debate. Harmful algal blooms have been noted since the late 1990s, and the extent of invasive aquatic macrophytes (both submerged and free-floating forms has increased especially during years of drought. Elevated nutrient loads must be considered in terms of their ability to support this excess biomass. Modern sensor technology and networks are now deployed that make high-frequency measurements of nitrate, ammonium, and phosphate. Data from such instruments allow a much more detailed assessment of the spatial and temporal dynamics of nutrients. Four fruitful directions for future research include utilizing continuous sensor data to estimate rates of primary production and ecosystem respiration, linking hydrodynamic models of the Delta with the transport and fate of dissolved nutrients, studying nutrient dynamics in various habitat types, and

  15. Centrifuge modelling of a laterally cyclic loaded pile

    DEFF Research Database (Denmark)

    Klinkvort, Rasmus Tofte; Leth, Caspar Thrane; Hededal, Ole

    2010-01-01

    A total number of 9 static and 6 cyclic centrifuge tests on laterally loaded piles in very dense, dry sand was erformed. The prototype dimensions of the piles were 1 meter in diameter and penetration depths varying from 6 to 10 meters. The static tests were used to investigate the initial subgrade...... reaction modulus and as a reference for cyclic tests. For the cyclic tests the accumulation of deflections and the change in secant stiffness of the soil from repetitive loading were investigated. From all the tests carried out accumulations of deflections were seen. rom the centrifuge tests it was seen...

  16. Residential Saudi load forecasting using analytical model and Artificial Neural Networks

    Science.gov (United States)

    Al-Harbi, Ahmad Abdulaziz

    In recent years, load forecasting has become one of the main fields of study and research. Short Term Load Forecasting (STLF) is an important part of electrical power system operation and planning. This work investigates the applicability of different approaches; Artificial Neural Networks (ANNs) and hybrid analytical models to forecast residential load in Kingdom of Saudi Arabia (KSA). These two techniques are based on model human modes behavior formulation. These human modes represent social, religious, official occasions and environmental parameters impact. The analysis is carried out on residential areas for three regions in two countries exposed to distinct people activities and weather conditions. The collected data are for Al-Khubar and Yanbu industrial city in KSA, in addition to Seattle, USA to show the validity of the proposed models applied on residential load. For each region, two models are proposed. First model is next hour load forecasting while second model is next day load forecasting. Both models are analyzed using the two techniques. The obtained results for ANN next hour models yield very accurate results for all areas while relatively reasonable results are achieved when using hybrid analytical model. For next day load forecasting, the two approaches yield satisfactory results. Comparative studies were conducted to prove the effectiveness of the models proposed.

  17. Development of a Dynamic Biomechanical Model for Load Carriage: Phase VI: Assessing Physiological and Biomechanical Loading Using the Portable Measurement System and the Dynamic Biomechanical Model

    Science.gov (United States)

    2007-12-01

    significantly in the trapezius, quadriceps , hamstrings , tibialis anterior and gastrocnemius, which supports Abe et al.’s (2004) statement that there is...model provides estimated reaction forces and moments on the lumbar spine, shoulder reaction force and total load experienced by the body as a ratio ...extra burden placed on the leg muscles by the load. The cost of walking per unit distance was obtained as the ratio of net VO2 (steady state VO2 minus

  18. Simple Models for Model-based Portfolio Load Balancing Controller Synthesis

    DEFF Research Database (Denmark)

    Edlund, Kristian Skjoldborg; Mølbak, Tommy; Bendtsen, Jan Dimon

    2010-01-01

    This paper presents a collection of models of so-called 'effectuators', i.e., subsystems in a power plant portfolio that represent control actions with associated dynamics and actuation costs. These models are derived in order to facilitate higher-level model-based control synthesis of a portfolio...... of generation units existing in an electrical power supply network, for instance in model-based predictive control or declarative control schemes. We focus on the effectuators found in the Danish power system. In particular, the paper presents models for boiler load, district heating, condensate throttling...... and wind turbine effectuators. Each model is validated against actual measurement data. Considering their simplicity, the models fit the observed data very well and are thus suitable for control purposes....

  19. Models for transport and fate of carbon, nutrients and point source released radionuclides to an aquatic ecosystem

    Energy Technology Data Exchange (ETDEWEB)

    Kumblad, Linda [Stockholm Univ. (Sweden). Dept. of Systems Ecology; Kautsky, Ulrik [Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden)

    2004-09-01

    In this report three ecosystem models are described in terms of structure, initial data, and results. All models are dynamic, mass-balanced and describe the transport and fate of elements in an open aquatic ecosystem. The models are based on ecologically sound principles, provide model results with high resolution and transparency, and are constrained by the nutrient dynamics of the ecosystem itself. The processes driving the transport in all the models are both the biological processes such as primary production, consumption, respiration and excretion, and abiotic e.g. water exchange and air-sea exchange. The first model, the CNP-model, describes the distribution and fluxes of carbon and nutrients for the coastal ecosystem off Forsmark. The second model, the C-14 model, is an extension of the CNP-model and describes the transport and distribution of hypothetically released C-14 from the underground repository SFR-1 to the ecosystem above. The third model, the RN-model, is a generic radionuclide flow model that models the transport and distribution of radionuclides other than C-14 hypothetically discharged to the ecosystem. The model also analyses the importance of some radionuclide specific mechanisms for the radionuclide flow. The generic radionuclide model is also based on the CNP-model, but has radionuclide specific mechanisms connected to each compartment.

  20. Models for transport and fate of carbon, nutrients and point source released radionuclides to an aquatic ecosystem

    International Nuclear Information System (INIS)

    Kumblad, Linda

    2004-09-01

    In this report three ecosystem models are described in terms of structure, initial data, and results. All models are dynamic, mass-balanced and describe the transport and fate of elements in an open aquatic ecosystem. The models are based on ecologically sound principles, provide model results with high resolution and transparency, and are constrained by the nutrient dynamics of the ecosystem itself. The processes driving the transport in all the models are both the biological processes such as primary production, consumption, respiration and excretion, and abiotic e.g. water exchange and air-sea exchange. The first model, the CNP-model, describes the distribution and fluxes of carbon and nutrients for the coastal ecosystem off Forsmark. The second model, the C-14 model, is an extension of the CNP-model and describes the transport and distribution of hypothetically released C-14 from the underground repository SFR-1 to the ecosystem above. The third model, the RN-model, is a generic radionuclide flow model that models the transport and distribution of radionuclides other than C-14 hypothetically discharged to the ecosystem. The model also analyses the importance of some radionuclide specific mechanisms for the radionuclide flow. The generic radionuclide model is also based on the CNP-model, but has radionuclide specific mechanisms connected to each compartment

  1. A Mixed Green Micro-Algal Model (MAMO) – Model Identification And Calibration Using Synthetic Medium And Nutrient Rich Carbon Depleted Wastewater

    DEFF Research Database (Denmark)

    Sæbø, M.; Valverde Perez, Borja; Van Wagenen, Jonathan

    The reuse of wastewater resources via micro-algal cultivation is a cost-effective and sustainable solution for third generation biofuel production. A process model, describing photobioreactor operation – also in combination with activated sludge processes, however, is still missing. In this paper......, we present a mathematical model, accounting for photoautotrophic and heterotrophic algal growth, nutrient uptake and storage in a mixed microalgae culture cultivated on nutrient rich carbon depleted (NRCD) wastewater. The process model is developed as an extension to the Activated Sludge Model 2d...

  2. Modelling of nutrient partitioning in growing pigs to predict their anatomical body composition. 2. Model evaluation

    NARCIS (Netherlands)

    Halas, V.; Dijkstra, J.; Babinszky, L.; Verstegen, M.W.A.; Gerrits, W.J.J.

    2004-01-01

    The objective of the present paper was to evaluate a dynamic mechanistic model for growing and fattening pigs presented in a companion paper. The model predicted the rate of protein and fat deposition (chemical composition), rate of tissue deposition (anatomical composition) and performance of pigs

  3. Aeroelastic Loads Modeling for Composite Aircraft Design Support

    NARCIS (Netherlands)

    Baluch, H.A.

    2009-01-01

    With regard to the simulation of structural vibrations and consequent aeroelastic loads in aircraft components, the use of elastic axis e.a as reference of vibrations is quite common. The e.a decouples the bending and torsion degrees of freedom (D.o.F) during the dynamic analysis. The use of the e.a

  4. Physical Modelling of Bucket Foundations Subjected to Axial Loading

    DEFF Research Database (Denmark)

    Vaitkunaite, Evelina

    Compared to oil and gas structures, marine renewable energy devices are usually much lighter, operate in shallower waters and are subjected to severe cyclic loading and dynamic excitations. These factors result in different structural behaviours. Bucket foundations are a potentially cost-effectiv...

  5. Transient multiphase flow modeling of gas well liquid loading

    NARCIS (Netherlands)

    Veeken, K.; Hu, B.; Schiferli, W.

    2009-01-01

    Gas well liquid loading occurs when gas production becomes insufficient to lift the associated liquids to surface. When that happens gas production first turns intermittent and eventually stops. Hence in depleting gas reservoirs the technical abandonment pressure and ultimate recovery are typically

  6. Monitoring of nutrient limitation in growing E. coli: a mathematical model of a ppGpp-based biosensor.

    Science.gov (United States)

    Pokhilko, Alexandra

    2017-11-21

    E. coli can be used as bacterial cell factories for production of biofuels and other useful compounds. The efficient production of the desired products requires careful monitoring of growth conditions and the optimization of metabolic fluxes. To avoid nutrient depletion and maximize product yields we suggest using a natural mechanism for sensing nutrient limitation, related to biosynthesis of an intracellular messenger - guanosine tetraphosphate (ppGpp). We propose a design for a biosensor, which monitors changes in the intracellular concentration of ppGpp by coupling it to a fluorescent output. We used mathematical modelling to analyse the intracellular dynamics of ppGpp, its fluorescent reporter, and cell growth in normal and fatty acid-producing E. coli lines. The model integrates existing mechanisms of ppGpp regulation and predicts the biosensor response to changes in nutrient state. In particular, the model predicts that excessive stimulation of fatty acid production depletes fatty acid intermediates, downregulates growth and increases the levels of ppGpp-related fluorescence. Our analysis demonstrates that the ppGpp sensor can be used for early detection of nutrient limitation during cell growth and for testing productivity of engineered lines.

  7. The Inclusion of Arbitrary Load Histories in the Strength Decay Model for Stress Rupture

    Science.gov (United States)

    Reeder, James R.

    2014-01-01

    Stress rupture is a failure mechanism where failures can occur after a period of time, even though the material has seen no increase in load. Carbon/epoxy composite materials have demonstrated the stress rupture failure mechanism. In a previous work, a model was proposed for stress rupture of composite overwrap pressure vessels (COPVs) and similar composite structures based on strength degradation. However, the original model was limited to constant load periods (holds) at constant load. The model was expanded in this paper to address arbitrary loading histories and specifically the inclusions of ramp loadings up to holds and back down. The broadening of the model allows for failures on loading to be treated as any other failure that may occur during testing instead of having to be treated as a special case. The inclusion of ramps can also influence the length of the "safe period" following proof loading that was previously predicted by the model. No stress rupture failures are predicted in a safe period because time is required for strength to decay from above the proof level to the lower level of loading. Although the model can predict failures during the ramp periods, no closed-form solution for the failure times could be derived. Therefore, two suggested solution techniques were proposed. Finally, the model was used to design an experiment that could detect the difference between the strength decay model and a commonly used model for stress rupture. Although these types of models are necessary to help guide experiments for stress rupture, only experimental evidence will determine how well the model may predict actual material response. If the model can be shown to be accurate, current proof loading requirements may result in predicted safe periods as long as 10(13) years. COPVs design requirements for stress rupture may then be relaxed, allowing more efficient designs, while still maintaining an acceptable level of safety.

  8. Dynamics of Nitrogen loads in surface water of an agricultural watershed by modelling approach, the Save, Southwest France.

    Science.gov (United States)

    Ferrant, S.; Oeurng, C.; Sauvage, S.; Durand, P.; Probst, J. L.; Sanchez-Perez, J. M.

    2009-04-01

    Agriculture is known to have a great impact of nutrients enrichment on continental water resources. In south-West of France (Gascogne region), water resource are essentially surface water and shallow aquifer. Nitrogen dynamic in river is complex and highly variable throughout season and year, depending on hydrology, landuse, removal in stream. In this context, agricultural impacts on nitrogen concentration are a matter of concern for agricultural decision-maker. In order to introduce sustainable land use concepts in this hilly, clayey and agricultural shallow soil context, the hydrological simulation model SWAT2005 has been tested as a valuable tool to evaluate the consequences of such land use changes on water and nutrient balance components. This semi-distributed hydrological model coupled with agronomical model EPIC is able to simulate the impact of each agricultural landuse at the outlet of the Save catchment (1100 km2). Hydrological parameters model are calibrated based on 14-year historical record (1994-2008). Nitrogen losses have been measured during 2 years (2006-2008) at the outlet and are used to validate the model calibration. Agricultural data at communal scale coupled with Spot image analyses have been used to evaluate agricultural distribution and pressure in SWAT. The aim of this modelling exercise is to simulate nitrogen cycle in whole agricultural Hydrological Response Units (HRU), depending on plant growth and culture rotation, to simulate accurately nitrate load in river. The ability of SWAT to reproduce nitrogen transfert and transformation at this scale and in this agricultural context will be evaluated by a discussion of importance of each nitrogen cycle process in nitrogen losses. SWAT could be a useful tool to test agricultural scenario to improve the nitrogen management in river.

  9. A model of rotationally-sampled wind turbulence for predicting fatigue loads in wind turbines

    Science.gov (United States)

    Spera, David A.

    1995-01-01

    Empirical equations are presented with which to model rotationally-sampled (R-S) turbulence for input to structural-dynamic computer codes and the calculation of wind turbine fatigue loads. These equations are derived from R-S turbulence data which were measured at the vertical-plane array in Clayton, New Mexico. For validation, the equations are applied to the calculation of cyclic flapwise blade loads for the NASA/DOE Mod-2 2.5-MW experimental HAWT's (horizontal-axis wind turbines), and the results compared to measured cyclic loads. Good correlation is achieved, indicating that the R-S turbulence model developed in this study contains the characteristics of the wind which produce many of the fatigue loads sustained by wind turbines. Empirical factors are included which permit the prediction of load levels at specified percentiles of occurrence, which is required for the generation of fatigue load spectra and the prediction of the fatigue lifetime of structures.

  10. Integration of MHD load models with circuit representations the Z generator.

    Energy Technology Data Exchange (ETDEWEB)

    Jennings, Christopher A.; Ampleford, David J.; Jones, Brent Manley; McBride, Ryan D.; Bailey, James E.; Jones, Michael C.; Gomez, Matthew Robert.; Cuneo, Michael Edward; Nakhleh, Charles; Stygar, William A.; Savage, Mark Edward; Wagoner, Timothy C.; Moore, James K.

    2013-03-01

    MHD models of imploding loads fielded on the Z accelerator are typically driven by reduced or simplified circuit representations of the generator. The performance of many of the imploding loads is critically dependent on the current and power delivered to them, so may be strongly influenced by the generators response to their implosion. Current losses diagnosed in the transmission lines approaching the load are further known to limit the energy delivery, while exhibiting some load dependence. Through comparing the convolute performance of a wide variety of short pulse Z loads we parameterize a convolute loss resistance applicable between different experiments. We incorporate this, and other current loss terms into a transmission line representation of the Z vacuum section. We then apply this model to study the current delivery to a wide variety of wire array and MagLif style liner loads.

  11. Seasonal Distributions of Global Ocean Chlorophyll and Nutrients: Analysis with a Coupled Ocean General Circulation Biogeochemical, and Radiative Model

    Science.gov (United States)

    Gregg, Watson W.

    1999-01-01

    A coupled general ocean circulation, biogeochemical, and radiative model was constructed to evaluate and understand the nature of seasonal variability of chlorophyll and nutrients in the global oceans. The model is driven by climatological meteorological conditions, cloud cover, and sea surface temperature. Biogeochemical processes in the model are determined from the influences of circulation and turbulence dynamics, irradiance availability, and the interactions among three functional phytoplankton groups (diatoms, chorophytes, and picoplankton) and three nutrient groups (nitrate, ammonium, and silicate). Phytoplankton groups are initialized as homogeneous fields horizontally and vertically, and allowed to distribute themselves according to the prevailing conditions. Basin-scale model chlorophyll results are in very good agreement with CZCS pigments in virtually every global region. Seasonal variability observed in the CZCS is also well represented in the model. Synoptic scale (100-1000 km) comparisons of imagery are also in good conformance, although occasional departures are apparent. Agreement of nitrate distributions with in situ data is even better, including seasonal dynamics, except for the equatorial Atlantic. The good agreement of the model with satellite and in situ data sources indicates that the model dynamics realistically simulate phytoplankton and nutrient dynamics on synoptic scales. This is especially true given that initial conditions are homogenous chlorophyll fields. The success of the model in producing a reasonable representation of chlorophyll and nutrient distributions and seasonal variability in the global oceans is attributed to the application of a generalized, processes-driven approach as opposed to regional parameterization, and the existence of multiple phytoplankton groups with different physiological and physical properties. These factors enable the model to simultaneously represent the great diversity of physical, biological

  12. An improved risk-explicit interval linear programming model for pollution load allocation for watershed management.

    Science.gov (United States)

    Xia, Bisheng; Qian, Xin; Yao, Hong

    2017-11-01

    Although the risk-explicit interval linear programming (REILP) model has solved the problem of having interval solutions, it has an equity problem, which can lead to unbalanced allocation between different decision variables. Therefore, an improved REILP model is proposed. This model adds an equity objective function and three constraint conditions to overcome this equity problem. In this case, pollution reduction is in proportion to pollutant load, which supports balanced development between different regional economies. The model is used to solve the problem of pollution load allocation in a small transboundary watershed. Compared with the REILP original model result, our model achieves equity between the upstream and downstream pollutant loads; it also overcomes the problem of greatest pollution reduction, where sources are nearest to the control section. The model provides a better solution to the problem of pollution load allocation than previous versions.

  13. Modeling and Analysis of Commercial Building Electrical Loads for Demand Side Management

    Science.gov (United States)

    Berardino, Jonathan

    In recent years there has been a push in the electric power industry for more customer involvement in the electricity markets. Traditionally the end user has played a passive role in the planning and operation of the power grid. However, many energy markets have begun opening up opportunities to consumers who wish to commit a certain amount of their electrical load under various demand side management programs. The potential benefits of more demand participation include reduced operating costs and new revenue opportunities for the consumer, as well as more reliable and secure operations for the utilities. The management of these load resources creates challenges and opportunities to the end user that were not present in previous market structures. This work examines the behavior of commercial-type building electrical loads and their capacity for supporting demand side management actions. This work is motivated by the need for accurate and dynamic tools to aid in the advancement of demand side operations. A dynamic load model is proposed for capturing the response of controllable building loads. Building-specific load forecasting techniques are developed, with particular focus paid to the integration of building management system (BMS) information. These approaches are tested using Drexel University building data. The application of building-specific load forecasts and dynamic load modeling to the optimal scheduling of multi-building systems in the energy market is proposed. Sources of potential load uncertainty are introduced in the proposed energy management problem formulation in order to investigate the impact on the resulting load schedule.

  14. Inverse analysis of aerodynamic loads from strain information using structural models and neural networks

    Science.gov (United States)

    Wada, Daichi; Sugimoto, Yohei

    2017-04-01

    Aerodynamic loads on aircraft wings are one of the key parameters to be monitored for reliable and effective aircraft operations and management. Flight data of the aerodynamic loads would be used onboard to control the aircraft and accumulated data would be used for the condition-based maintenance and the feedback for the fatigue and critical load modeling. The effective sensing techniques such as fiber optic distributed sensing have been developed and demonstrated promising capability of monitoring structural responses, i.e., strains on the surface of the aircraft wings. By using the developed techniques, load identification methods for structural health monitoring are expected to be established. The typical inverse analysis for load identification using strains calculates the loads in a discrete form of concentrated forces, however, the distributed form of the loads is essential for the accurate and reliable estimation of the critical stress at structural parts. In this study, we demonstrate an inverse analysis to identify the distributed loads from measured strain information. The introduced inverse analysis technique calculates aerodynamic loads not in a discrete but in a distributed manner based on a finite element model. In order to verify the technique through numerical simulations, we apply static aerodynamic loads on a flat panel model, and conduct the inverse identification of the load distributions. We take two approaches to build the inverse system between loads and strains. The first one uses structural models and the second one uses neural networks. We compare the performance of the two approaches, and discuss the effect of the amount of the strain sensing information.

  15. A hill-type muscle model expansion accounting for effects of varying transverse muscle load.

    Science.gov (United States)

    Siebert, Tobias; Stutzig, Norman; Rode, Christian

    2018-01-03

    Recent studies demonstrated that uniaxial transverse loading (F G ) of a rat gastrocnemius medialis muscle resulted in a considerable reduction of maximum isometric muscle force (ΔF im ). A hill-type muscle model assuming an identical gearing G between both ΔF im and F G as well as lifting height of the load (Δh) and longitudinal muscle shortening (Δl CC ) reproduced experimental data for a single load. Here we tested if this model is able to reproduce experimental changes in ΔF im and Δh for increasing transverse loads (0.64 N, 1.13 N, 1.62 N, 2.11 N, 2.60 N). Three different gearing ratios were tested: (I) constant G c representing the idea of a muscle specific gearing parameter (e.g. predefined by the muscle geometry), (II) G exp determined in experiments with varying transverse load, and (III) G f that reproduced experimental ΔF im for each transverse load. Simulations using G c overestimated ΔF im (up to 59%) and Δh (up to 136%) for increasing load. Although the model assumption (equal G for forces and length changes) held for the three lower loads using G exp and G f , simulations resulted in underestimation of ΔF im by 38% and overestimation of Δh by 58% for the largest load, respectively. To simultaneously reproduce experimental ΔF im and Δh for the two larger loads, it was necessary to reduce F im by 1.9% and 4.6%, respectively. The model seems applicable to account for effects of muscle deformation within a range of transverse loading when using a linear load-dependent function for G. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Tree species identity and interactions with neighbors determine nutrient leaching in model tropical forests.

    Science.gov (United States)

    Ewel, John J; Bigelow, Seth W

    2011-12-01

    An ecosystem containing a mixture of species that differ in phenology, morphology, and physiology might be expected to resist leaching of soil nutrients to a greater extent than one composed of a single species. We tested the effects of species identity and plant-life-form richness on nutrient leaching at a lowland tropical site where deep infiltration averages >2 m year(-1). Three indigenous tree species with contrasting leafing phenologies (evergreen, dry-season deciduous, and wet-season deciduous) were grown in monoculture and together with two other life-forms with which they commonly occur in tropical forests: a palm and a giant, perennial herb. To calculate nutrient leaching over an 11-year period, concentrations of nutrients in soil water were multiplied by drainage rates estimated from a water balance. The effect of plant-life-form richness on retention differed according to tree species identity and nutrient. Nitrate retention was greater in polycultures of the dry-season deciduous tree species (mean of 7.4 kg ha(-1) year(-1) of NO(3)-N lost compared to 12.7 in monoculture), and calcium and magnesium retention were greater in polycultures of the evergreen and wet-season deciduous tree species. Complementary use of light led to intensification of soil exploitation by roots, the main agent responsible for enhanced nutrient retention in some polycultures. Other mechanisms included differences in nutrient demand among species, and avoidance of catastrophic failure due to episodic weather events or pest outbreaks. Even unrealistically simple multi-life-form mimics of tropical forest can safeguard a site's nutrient capital if careful attention is paid to species' characteristics and temporal changes in interspecific interactions.

  17. T-Craft Seabase Ramp Loads Model Test Data Report

    Science.gov (United States)

    2010-12-01

    connections and relative motions of the seabase. 15. SUBJECT TERMS Seabase, Seakeeping, LMSR, T-Craft, Ramp Loads 16. SECURITY CLASSIFICATION OF: a. REPORT...Acceleration 39 Applied Geomechanics Pro 3600 and Tilt Table 39 Acceleration Calibration by Inclination 39 Local Acceleration of Gravity 41...limit will be larger than the calibration uncertainty, especially when surface waves are involved. Acceleration Applied Geomechanics Pro 3600 and Tilt

  18. SMR Re-Scaling and Modeling for Load Following Studies

    Energy Technology Data Exchange (ETDEWEB)

    Hoover, K.; Wu, Q.; Bragg-Sitton, S.

    2016-11-01

    This study investigates the creation of a new set of scaling parameters for the Oregon State University Multi-Application Small Light Water Reactor (MASLWR) scaled thermal hydraulic test facility. As part of a study being undertaken by Idaho National Lab involving nuclear reactor load following characteristics, full power operations need to be simulated, and therefore properly scaled. Presented here is the scaling analysis and plans for RELAP5-3D simulation.

  19. Multiple constraint modeling of nutrient cycling stoichiometry following forest clearing and pasture abandonment in the Eastern Amazon

    Science.gov (United States)

    Davidson, Eric; Nifong, Rachel

    2017-04-01

    While deforestation has declined since its peak, land-use change continues to modify Amazonian landscapes. The responses and feedbacks of biogeochemical cycles to these changes play an important role in determining possible future trajectories of ecosystem function and for land stewardship through effects on rates of secondary forest regrowth, soil emissions of greenhouse gases, inputs of nutrients to groundwater and streamwater, and nutrient management in agroecosystems. Here we present a new synthetic analyses of data from the NASA-supported LBA-ECO project and others datasets on nutrient cycling in cattle pastures, secondary forests, and mature forests at Paragominas, Pará, Brazil. We have developed a stoichiometric model relating C-N-P interactions during original forest clearing, extensive and intensive pasture management, and secondary forest regrowth, constrained by multiple observations of ecosystem stocks and fluxes in each land use. While P is conservatively cycled in all land uses, we demonstrate that pyrolyzation of N during pasture formation and during additional burns for pasture management depletes available-N pools, consistent with observations of lower rates of N leaching and trace gas emission and consistent with secondary forest growth responses to experimental N amendments. The soils store large stocks of N and P, and our parameterization of available forms of these nutrients for steady-state dynamics in the mature forest yield reasonable estimates of net N and P mineralization available for grasses and secondary forest species at rates consistent with observed biomass accumulation and productivity in these modified ecosystems. Because grasses and forests have much different demands for N relative to P, the land use has important biogeochemical impacts. The model demonstrates the need for periodic P inputs for sustainable pasture management and for a period of significant biological N fixation for early-to-mid-successional secondary forest

  20. An anisotropic damage model for concrete structures under cyclic loading-uniaxial modeling

    Science.gov (United States)

    Long, Yuchuan; He, Yuming

    2017-05-01

    An anisotropic damage model is developed based on conventional rotating crack approach. It uses nonlinear unloading/linear reloading branches to model the hysteretic behavior of concrete. Two damage variables, determined by the ratio of accumulated dissipating energy to fracture energy, are introduced to represent the stiffness degradation in tension and compression. Three cyclic tests are simulated by this model and sensitivity analyses are conducted as well. The numerical responses calculated by the damage model are consistent with those obtained from the experiments. The numerical results reflect the nonlinear behavior observed in those tests, such as the damage-induced stiffness degradation, accumulation of residual deformation, energy dissipation caused by hysteretic behavior and stiffness recovery effect due to crack closure. Sensitivity analyses show that the damage exponents have significant influence on the computational accuracy. It is concluded that the anisotropic damage model is applicable to the nonlinear analyses of concrete structures subjected to cyclic loading.

  1. Design and Modelling of Thermostatically Controlled Loads as Frequency Controlled Reserve

    DEFF Research Database (Denmark)

    Xu, Zhao; Østergaard, Jacob; Togeby, Mikael

    2007-01-01

    Using demand as frequency controlled reserve (DFR) is beneficial to power systems in many aspects. To study the impacts of this technology on power system operation, control logics and simulation models of relevant loads should be carefully developed. Two advanced control logics for using demand...... frequency, is developed. The developed simulation model is able to represent a variety of aggregated thermostatically controlled loads, such as heaters or refrigerators. Uncertainties including customer behaviours and ambient temperature variation are also modelled. Preliminary simulation results...

  2. The design of models for cryogenic wind tunnels. [mechanical properties and loads

    Science.gov (United States)

    Gillespie, V. P.

    1977-01-01

    Factors to be considered in the design and fabrication of models for cryogenic wind tunnels include high model loads imposed by the high operating pressures, the mechanical and thermodynamic properties of materials in low temperature environments, and the combination of aerodynamic loads with the thermal environment. Candidate materials are being investigated to establish criteria for cryogenic wind tunnel models and their installation. Data acquired from these tests will be provided to users of the National Transonic Facility.

  3. Load modeling for sharp V-cutter cutting litchi (Litchi chinensis Sonn ...

    African Journals Online (AJOL)

    Yomi

    2012-02-16

    Feb 16, 2012 ... Integrating picking institutions with autocontrol method led to the development of a new innovative. 'hand-held auto-picker' for litchi (Litchi chinensis Sonn.) harvesting. Cutting load is a key parameter for. 'hand-held auto-picker' operation. However, there is still no suitable model for cutting load setting.

  4. An optimal control model for load shifting - With application in the energy management of a colliery

    International Nuclear Information System (INIS)

    Middelberg, Arno; Zhang Jiangfeng; Xia Xiaohua

    2009-01-01

    This paper presents an optimal control model for the load shifting problem in energy management and its application in a South African colliery. It is illustrated in the colliery scenario that how the optimal control model can be applied to optimize load shifting and improve energy efficiency through the control of conveyor belts. The time-of-use electricity tariff is used as an input to the objective function in order to obtain a solution that minimizes electricity costs and thus maximizes load shifting. The case study yields promising results that show the potential of applying this optimal control model to other industrial Demand Side Management initiatives

  5. Physical scale modeling of single free head piles under lateral loading in cohesive soils

    Directory of Open Access Journals (Sweden)

    Edgar Leonardo Salamanca-Medina

    2017-06-01

    Full Text Available This paper presents the results of the small scale modeling of free head wood piles under horizontal loading in cohesive soils, tested in order to compare the results with analytical models proposed by various authors. Characteristic Load (CLM and P-Y Curves methods were used for the prediction of lateral deflections at the head of the piles and the method proposed by Broms for estimating the ultimate lateral load. These predictions were compared with the results of the physical modeling, obtaining a good approximation between them.

  6. Modeling the Tensile Strength of Carbon Fiber - Reinforced Ceramic - Matrix Composites Under Multiple Fatigue Loading

    Science.gov (United States)

    Li, Longbiao

    2016-06-01

    An analytical method has been developed to investigate the effect of interface wear on the tensile strength of carbon fiber - reinforced ceramic - matrix composites (CMCs) under multiple fatigue loading. The Budiansky - Hutchinson - Evans shear - lag model was used to describe the micro stress field of the damaged composite considering fibers failure and the difference existed in the new and original interface debonded region. The statistical matrix multicracking model and fracture mechanics interface debonding criterion were used to determine the matrix crack spacing and interface debonded length. The interface shear stress degradation model and fibers strength degradation model have been adopted to analyze the interface wear effect on the tensile strength of the composite subjected to multiple fatigue loading. Under tensile loading, the fibers failure probabilities were determined by combining the interface wear model and fibers failure model based on the assumption that the fiber strength is subjected to two - parameter Weibull distribution and the loads carried by broken and intact fibers satisfy the Global Load Sharing criterion. The composite can no longer support the applied load when the total loads supported by broken and intact fibers approach its maximum value. The conditions of a single matrix crack and matrix multicrackings for tensile strength corresponding to multiple fatigue peak stress levels and different cycle number have been analyzed.

  7. Modeling and Depletion Simulations for a High Flux Isotope Reactor Cycle with a Representative Experiment Loading

    Energy Technology Data Exchange (ETDEWEB)

    Chandler, David [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Reactor and Nuclear Systems Division; Betzler, Ben [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Reactor and Nuclear Systems Division; Hirtz, Gregory John [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Reactor and Nuclear Systems Division; Ilas, Germina [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Reactor and Nuclear Systems Division; Sunny, Eva [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Reactor and Nuclear Systems Division

    2016-09-01

    The purpose of this report is to document a high-fidelity VESTA/MCNP High Flux Isotope Reactor (HFIR) core model that features a new, representative experiment loading. This model, which represents the current, high-enriched uranium fuel core, will serve as a reference for low-enriched uranium conversion studies, safety-basis calculations, and other research activities. A new experiment loading model was developed to better represent current, typical experiment loadings, in comparison to the experiment loading included in the model for Cycle 400 (operated in 2004). The new experiment loading model for the flux trap target region includes full length 252Cf production targets, 75Se production capsules, 63Ni production capsules, a 188W production capsule, and various materials irradiation targets. Fully loaded 238Pu production targets are modeled in eleven vertical experiment facilities located in the beryllium reflector. Other changes compared to the Cycle 400 model are the high-fidelity modeling of the fuel element side plates and the material composition of the control elements. Results obtained from the depletion simulations with the new model are presented, with a focus on time-dependent isotopic composition of irradiated fuel and single cycle isotope production metrics.

  8. Development of the hybrid cells in series model to simulate ammonia nutrient pollutant transport along the Umgeni River.

    Science.gov (United States)

    Olowe, Kayode O; Kumarasamy, Muthukrishnavellaisamy

    2017-10-01

    Discharge of organic waste results in high nutrient pollution of the water bodies which is a major menace to the environment. A high quantity of nutrients such as ammonia causes a reduction in the dissolved oxygen level and induces algal growth in the water bodies. Water quality models have been the tools to evaluate the rate at which streams can disperse the pollutants they receive. Many water quality models are flawed either because of their inadequacy to completely simulate the advection component of the pollutant transport, or because of the limited application of the models, due to inaccurate estimation of model parameters. The hybrid cell in series (HCIS) developed by Ghosh et al. (2004) has been able to overcome such difficulties associated with the mixing cell-based models. Thus, the current study focuses on developing an analytical solution for the pollutant transport of the ammonia concentration through the plug flow, the first and second well-mixed cells of the HCIS model. The HCIS model coupled with the first order kinetic equation for ammonia nutrient was developed to simulate the ammonia pollutant concentration in the water column. The ammonia concentration at various points along the river system was assessed by considering the effects of the transformation of ammonia to nitrite, the uptake of ammonia by the algae, the respiration rate of the algae and the input of benthic source to the ammonia concentration in the water column. The proposed model was tested using synthetic data, and the HCIS-NH 3 model simulations for spatial and temporal variation of ammonia pollutant transport were analysed. The simulated results of the HCIS-NH 3 model agreed with the Fickian-based advection-dispersion equation (ADE) for simulating ammonia concentration solved using an explicit finite difference scheme. The HCIS-NH 3 model also showed a good agreement with the observed data from the Umgeni River, except during rainy periods.

  9. An ENSO-Based Multivariate Wavelet-Decomposition Time Series Model for Nitrate Loads in the Little River Watershed

    Science.gov (United States)

    The El-Nino/Southern Oscillation (ENSO) is a periodic global climate phenomenon with strong effects on the weather patterns of the southeast United States. ENSO has been shown to have predictable effects on stream flow, rainfall, crop yield, and nutrient loads in runoff. In monitoring and research e...

  10. Assessing the fate of nutrients and carbon in the bioenergy chain through the modeling of biomass growth and conversion.

    Science.gov (United States)

    François, Jessica; Fortin, Mathieu; Patisson, Fabrice; Dufour, Anthony

    2014-12-02

    A forest growth model was coupled to a model of combined heat and power (CHP) production in a gasification plant developed in Aspen Plus. For a given production, this integrated forest-to-energy model made it possible to predict the annual flows in wood biomass, carbon, and nutrients, including N, S, P, and K, from the forest to the air emissions (NOx, SOx, PAH, etc.) and ash flows. We simulated the bioenergy potential of pure even-aged high-forest stands of European beech, an abundant forest type in Northeastern France. Two forest management practices were studied, a standard-rotation and a shorter-rotation scenario, along with two wood utilizations: with or without fine woody debris (FWD) harvesting. FWD harvesting tended to reduce the forested area required to supply the CHP by 15–22% since larger amounts of energy wood were available for the CHP process, especially in the short-rotation scenario. Because less biomass was harvested, the short-rotation scenario with FWD decreased the nutrient exports per hectare and year by 4–21% compared to standard practices but increased the amount of N, S, and P in the CHP process by 2–9%. This increase in the input nutrient flows had direct consequences on the inorganic air emissions, thus leading to additional NOx and SO2 emissions. This model is a valuable tool for assessing the life cycle inventories of the entire bioenergy chain.

  11. Modelling the flow of nitrogen and phosphorus in Europe: From loads to coastal seas

    NARCIS (Netherlands)

    Klepper O; Beusen AHW; Meinardi CR; CIM; LWD; LBG

    1995-01-01

    A model is described that aims at predicting surface water quality from N- and P-inputs on a European scale. The model combines a GIS-based approach to estimate loads, geohydrological data to define model structure and statistical techniques to estimate parameter values. The model starts with an

  12. A simplified model predicting the weight of the load carrying beam in a wind turbine blade

    DEFF Research Database (Denmark)

    Mikkelsen, Lars Pilgaard

    2016-01-01

    Based on a simplified beam model, the loads, stresses and deflections experienced by a wind turbine blade of a given length is estimated. Due to the simplicity of the model used, the model is well suited for work investigating scaling effects of wind turbine blades. Presently, the model is used t...

  13. Effects of electric and magnetic loadings on bone surface remodeling: a model modification and simulation.

    Science.gov (United States)

    Kazerooni, Anahita Fathi; Rabbani, Mohsen; Yazdchi, Mohammadreza; Kasiri, Saeid; Rad, Hamidreza Saligheh

    2011-06-01

    This paper presents a new modification to the previous model of bone surface remodeling under electric and magnetic loadings. For this study, the thermo-electro-magneto-elastic model of bone surface remodeling is used. This model is modified by considering an important phenomenon occurring in living bone through its adaptation to external loadings called desensitization. In fact, bone cells lose their responsiveness and sensitivity to long-term external loadings, i.e., they become desensitized. Therefore, bone cells need a recovery period, during which they become resensitized. In this work, this phenomenon is considered in the original model. The effects of various electric and magnetic loading conditions, including various frequencies, waveforms and pulse duty cycles, are explored on the modified model and compared to the original model. The modified model is also searched for the optimal frequency and duty cycle, to obtain the best bone growth response under electromagnetic fields. The results of this paper show that the modified model is consistent with experimental observations. In addition, it is indicated that this modified model in contrast to the original model, is sensitive to frequency. It is shown that the optimal frequency of loading for the modified model is 1 Hertz (Hz), and the pulse duty cycles up to 50% are sufficient for bone remodeling to reach its maximum value.

  14. SAFARI 2000 Modeled Fuel Load in Southern Africa, 1999-2000

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains global, spatially explicit (1 km2 grid cells) and temporally explicit (semi-monthly) modeled output of fuel loads over southern Africa. The...

  15. Modeling drivers of phosphorus loads in Chesapeake Bay tributaries and inferences about long-term change

    Science.gov (United States)

    Ryberg, Karen R.; Blomquist, Joel; Sprague, Lori A.; Sekellick, Andrew J.; Keisman, Jennifer

    2018-01-01

    Causal attribution of changes in water quality often consists of correlation, qualitative reasoning, listing references to the work of others, or speculation. To better support statements of attribution for water-quality trends, structural equation modeling was used to model the causal factors of total phosphorus loads in the Chesapeake Bay watershed. By transforming, scaling, and standardizing variables, grouping similar sites, grouping some causal factors into latent variable models, and using methods that correct for assumption violations, we developed a structural equation model to show how causal factors interact to produce total phosphorus loads. Climate (in the form of annual total precipitation and the Palmer Hydrologic Drought Index) and anthropogenic inputs are the major drivers of total phosphorus load in the Chesapeake Bay watershed. Increasing runoff due to natural climate variability is offsetting purposeful management actions that are otherwise decreasing phosphorus loading; consequently, management actions may need to be reexamined to achieve target reductions in the face of climate variability.

  16. Characterization of non-linear household loads for frequency domain modeling

    Directory of Open Access Journals (Sweden)

    Miguel Fernando Romero

    2015-06-01

    Full Text Available Component-based harmonic studies in public Low Voltage grids require realistic models of individual loads as well as their typical penetration ratios. As fundamental basis for the development of comprehensive models for residential users, this paper identifies the most commonly used household loads in Colombia. The loads are classified according to their Power Factor Correction (PFC circuit topology in no-PFC, passive-PFC and active-PFC devices, and a comprehensive set of loads is selected. Their behavior in terms of harmonic emission is characterized by intensive lab measurements with systematically varied supply voltage distortion. Based on several indices, the suitability of different frequency-domain modeling approaches (e.g. constant current source, decoupled and coupled Norton models is assessed.

  17. Probabilistic modeling of nodal electric vehicle load due to fast charging stations

    DEFF Research Database (Denmark)

    Tang, Difei; Wang, Peng; Wu, Qiuwei

    2016-01-01

    operation of both traffic and power systems. This paper proposes a probabilistic approach to model the nodal EV load at fast charging stations in integrated power and transport systems. Following the introduction of the spatial-temporal model of moving EV loads, we extended the model by taking fast charging...... station into consideration. Fuzzy logic inference system is applied to simulate the charging decision of EV drivers at fast charging station. Due to increasing EV loads in power system, the potential traffic congestion in fast charging stations is modeled and evaluated by queuing theory with spatial......-temporal varying arrival and service rates. The time-varying nodal EV loads are obtained by the number of operating fast chargers at each node of the power system. System studies demonstrate that the combination of AC normal and DC charging may share the EV charging demand and alleviate the impact to power system...

  18. SAFARI 2000 Modeled Fuel Load in Southern Africa, 1999-2000

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: This data set contains global, spatially explicit (1 km2 grid cells) and temporally explicit (semi-monthly) modeled output of fuel loads over southern...

  19. Modeling and CFD Simulation of nutrient Distribution in picoliter bioreactors for bacterial growth studies on single-cell level

    OpenAIRE

    Westerwalbesloh, Christoph; Grünberger, Alexander; Stute, Birgit; Weber, Sophie; Wiechert, Wolfgang; Kohlheyer, Dietrich; von Lieres, Eric

    2015-01-01

    A microfluidic device for microbial single-cell cultivation of bacteria was modeled and simulated using COMSOL Multiphysics. The liquid velocity field and the mass transfer within the supply channels and cultivation chambers were calculated to gain insight in the distribution of supplied nutrients and metabolic products secreted by the cultivated bacteria. The goal was to identify potential substrate limitations or product accumulations within the cultivation device. The metabolic uptake and ...

  20. Sources and delivery of carbon, nitrogen, and phosphorus to the coastal zone: An overview of global Nutrient Export from Watersheds (NEWS) models and their application

    NARCIS (Netherlands)

    Seitzinger, S.P.; Harrison, J.A.; Dumont, E.L.; Beusen, A.H.W.; Bouwman, A.F.

    2005-01-01

    An overview of the first spatially explicit, multielement (N, P, and C), multiform (dissolved inorganic: DIN, DIP; dissolved organic: DOC, DON, DOP; and particulate: POC, PN, PP) predictive model system of river nutrient export from watersheds (Global Nutrient Export from Watersheds (NEWS)) is

  1. Simplified rotor load models and fatigue damage estimates for offshore wind turbines.

    Science.gov (United States)

    Muskulus, M

    2015-02-28

    The aim of rotor load models is to characterize and generate the thrust loads acting on an offshore wind turbine. Ideally, the rotor simulation can be replaced by time series from a model with a few parameters and state variables only. Such models are used extensively in control system design and, as a potentially new application area, structural optimization of support structures. Different rotor load models are here evaluated for a jacket support structure in terms of fatigue lifetimes of relevant structural variables. All models were found to be lacking in accuracy, with differences of more than 20% in fatigue load estimates. The most accurate models were the use of an effective thrust coefficient determined from a regression analysis of dynamic thrust loads, and a novel stochastic model in state-space form. The stochastic model explicitly models the quasi-periodic components obtained from rotational sampling of turbulent fluctuations. Its state variables follow a mean-reverting Ornstein-Uhlenbeck process. Although promising, more work is needed on how to determine the parameters of the stochastic model and before accurate lifetime predictions can be obtained without comprehensive rotor simulations. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  2. SWAT Model Prediction of Phosphorus Loading in a South Carolina Karst Watershed with a Downstream Embayment

    Science.gov (United States)

    Devendra M. Amatya; Manoj K. Jha; Thomas M. Williams; Amy E. Edwards; Daniel R.. Hitchcock

    2013-01-01

    The SWAT model was used to predict total phosphorus (TP) loadings for a 1555-ha karst watershed—Chapel Branch Creek (CBC)—which drains to a lake via a reservoir-like embayment (R-E). The model was first tested for monthly streamflow predictions from tributaries draining three potential source areas as well as the downstream R-E, followed by TP loadings using data...

  3. High-Speed Shaft Bearing Loads Testing and Modeling in the NREL Gearbox Reliability Collaborative: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    McNiff, B.; Guo, Y.; Keller, J.; Sethuraman, L.

    2014-12-01

    Bearing failures in the high speed output stage of the gearbox are plaguing the wind turbine industry. Accordingly, the National Renewable Energy Laboratory (NREL) Gearbox Reliability Collaborative (GRC) has performed an experimental and theoretical investigation of loads within these bearings. The purpose of this paper is to describe the instrumentation, calibrations, data post-processing and initial results from this testing and modeling effort. Measured HSS torque, bending, and bearing loads are related to model predictions. Of additional interest is examining if the shaft measurements can be simply related to bearing load measurements, eliminating the need for invasive modifications of the bearing races for such instrumentation.

  4. Nutrient limitation reduces land carbon uptake in simulations with a model of combined carbon, nitrogen and phosphorus cycling

    Directory of Open Access Journals (Sweden)

    D. S. Goll

    2012-09-01

    Full Text Available Terrestrial carbon (C cycle models applied for climate projections simulate a strong increase in net primary productivity (NPP due to elevated atmospheric CO2 concentration during the 21st century. These models usually neglect the limited availability of nitrogen (N and phosphorus (P, nutrients that commonly limit plant growth and soil carbon turnover. To investigate how the projected C sequestration is altered when stoichiometric constraints on C cycling are considered, we incorporated a P cycle into the land surface model JSBACH (Jena Scheme for Biosphere–Atmosphere Coupling in Hamburg, which already includes representations of coupled C and N cycles.

    The model reveals a distinct geographic pattern of P and N limitation. Under the SRES (Special Report on Emissions Scenarios A1B scenario, the accumulated land C uptake between 1860 and 2100 is 13% (particularly at high latitudes and 16% (particularly at low latitudes lower in simulations with N and P cycling, respectively, than in simulations without nutrient cycles. The combined effect of both nutrients reduces land C uptake by 25% compared to simulations without N or P cycling. Nutrient limitation in general may be biased by the model simplicity, but the ranking of limitations is robust against the parameterization and the inflexibility of stoichiometry. After 2100, increased temperature and high CO2 concentration cause a shift from N to P limitation at high latitudes, while nutrient limitation in the tropics declines. The increase in P limitation at high-latitudes is induced by a strong increase in NPP and the low P sorption capacity of soils, while a decline in tropical NPP due to high autotrophic respiration rates alleviates N and P limitations. The quantification of P limitation remains challenging. The poorly constrained processes of soil P sorption and biochemical mineralization are identified as the main uncertainties in the strength of P limitation

  5. Development of SWITCH-Hawaii model: loads and renewable resources.

    Science.gov (United States)

    2016-08-01

    This report summarizes work done to configure the SWITCH power system model using data for the Oahu power system. SWITCH is a planning model designed to choose optimal infrastructure investments for power systems over a multi-decade period. Investmen...

  6. FAST Mast Structural Response to Axial Loading: Modeling and Verification

    Science.gov (United States)

    Knight, Norman F., Jr.; Elliott, Kenny B.; Templeton, Justin D.; Song, Kyongchan; Rayburn, Jeffery T.

    2012-01-01

    The International Space Station s solar array wing mast shadowing problem is the focus of this paper. A building-block approach to modeling and analysis is pursued for the primary structural components of the solar array wing mast structure. Starting with an ANSYS (Registered Trademark) finite element model, a verified MSC.Nastran (Trademark) model is established for a single longeron. This finite element model translation requires the conversion of several modeling and analysis features for the two structural analysis tools to produce comparable results for the single-longeron configuration. The model is then reconciled using test data. The resulting MSC.Nastran (Trademark) model is then extended to a single-bay configuration and verified using single-bay test data. Conversion of the MSC. Nastran (Trademark) single-bay model to Abaqus (Trademark) is also performed to simulate the elastic-plastic longeron buckling response of the single bay prior to folding.

  7. Modelling of dynamic strain aging with a dislocation based isotropic hardening model and investigation of orthogonal loading

    NARCIS (Netherlands)

    Berisha, B.; Hora, P.; Tong, L.; Wahlen, A.; van den Boogaard, Antonius H.; Yang, D.Y.

    2009-01-01

    Based on experimental results, a dislocation material model describing the dynamic strain aging effect at different temperatures is presented. One and two stage loading tests were performed in order to investigate the influence of the loading direction as well as the temperature influence due to the

  8. Modeling on the Effect of Coal Loads on Kinetic Energy of Balls for Ball Mills

    Directory of Open Access Journals (Sweden)

    Yan Bai

    2015-07-01

    Full Text Available This paper presents a solution for the detection and control of coal loads that is more accurate and convenient than those currently used. To date, no research has addressed the use of a grinding medium as the controlled parameter. To improve the accuracy of the coal load detection based on the kinetic energy of balls in a tubular ball mill, a Discrete Element Method (DEM model for ball kinematics based on coal loads is proposed. The operating process for a ball mill and the ball motion, as influenced by the coal quality and the coal load, was analyzed carefully. The relationship between the operating efficiency of a coal pulverizing system, coal loads, and the balls’ kinetic energy was obtained. Origin and Matlab were utilized to draw the variation of parameters with increasing coal loads in the projectile and cascading motion states. The parameters include the balls’ real-time kinetic energy, the friction energy consumption, and the mill’s total work. Meanwhile, a method of balanced adjacent degree and a physical experiment were proposed to verify the considerable effect of the balls’ kinetic energy on coal loads. The model and experiment results indicate that a coal load control method based on the balls’ kinetic energy is therefore feasible for the optimized operation of a coal pulverizing system.

  9. Design And Modeling An Automated Digsilent Power System For Optimal New Load Locations

    Directory of Open Access Journals (Sweden)

    Mohamed Saad

    2015-08-01

    Full Text Available Abstract The electric power utilities seek to take advantage of novel approaches to meet growing energy demand. Utilities are under pressure to evolve their classical topologies to increase the usage of distributed generation. Currently the electrical power engineers in many regions of the world are implementing manual methods to measure power consumption for farther assessment of voltage violation. Such process proved to be time consuming costly and inaccurate. Also demand response is a grid management technique where retail or wholesale customers are requested either electronically or manually to reduce their load. Therefore this paper aims to design and model an automated power system for optimal new load locations using DPL DIgSILENT Programming Language. This study is a diagnostic approach that assists system operator about any voltage violation cases that would happen during adding new load to the grid. The process of identifying the optimal bus bar location involves a complicated calculation of the power consumptions at each load bus As a result the DPL program would consider all the IEEE 30 bus internal networks data then a load flow simulation will be executed. To add the new load to the first bus in the network. Therefore the developed model will simulate the new load at each available bus bar in the network and generate three analytical reports for each case that captures the overunder voltage and the loading elements among the grid.

  10. MODELING OF THE SNOW LOAD ON THE ROOFS OF INDUSTRIAL BUILDINGS

    Directory of Open Access Journals (Sweden)

    Zolina Tat’yana Vladimirovna

    2016-08-01

    Full Text Available When designing load-bearing framework structures using the method of limiting states it is necessary to determine the maximum possible value of snow load for the entire period of operation of an industrial building for the possibility of transition. The magnitude of the snow load is randomly changed over the time, and therefore the most appropriate form of its display is a probabilistic model of random process. The authors have identified the most preferable approach to modeling of snow load. It consists in presenting a selective sequence of the year maximums in the form of a continuous random variable distributed according to the Gumbel law. Its parameters are expressed through the mathematical expectation and the standard sample set of meteorological observations. According to the calculated values of the parameters the authors have built a graphic interpretation of the law of distribution of this random variable. When building a model of the total snow load on the roof of a building the influence of various factors should be considered, such as: • snow shedding at a given roof slope; • snow movement caused by wind; • distribution of snow depending on the roof shape; • snow melting depending on the thermal characteristics of the roof; • the ability to drain meltwater from the surface of the roof. The resulting model of snow load is adapted for implementation using software complex “DINCIB-new” developed by the authors. The proposed approach to the modeling of the snow load on the roof of an industrial building allows correlating the repeatability period of its limit calculated value with the residual life of the research object. This has become possible due to the multiple implementation of an automated algorithm for calculating an industrial building, which was developed by the authors, with account of the varying values of snow load in relation to the corresponding mathematical expectation, with registering the quantities of

  11. Mechatronic FEM model of an electromagnetic-force-compensated load cell

    International Nuclear Information System (INIS)

    Weis, Hanna; Hilbrunner, Falko; Fröhlich, Thomas; Jäger, Gerd

    2012-01-01

    In this paper, a mechatronic model for an electromagnetic-force-compensated (EMC) load cell is presented. Designed in ANSYS Mechanical APDL®, the model consists of two modules: the mechanical behaviour of the load cell is represented by a FEM model. The electronic and the electromagnetic parts, consisting of a position indicator, controller and electromagnetic actuator, are implemented into the model as a set of differential equations via ANSYS Parametric Design Language (APDL). Optimization of the mechanical, electromagnetic and controller components can be performed using this model, as well as experiments to determine the sensitivity of the complete system to changes of environmental properties, e.g., the stiffness of the support. (paper)

  12. Effects of mechanical loading on cortical defect repair using a novel mechanobiological model of bone healing.

    Science.gov (United States)

    Liu, Chao; Carrera, Robert; Flamini, Vittoria; Kenny, Lena; Cabahug-Zuckerman, Pamela; George, Benson M; Hunter, Daniel; Liu, Bo; Singh, Gurpreet; Leucht, Philipp; Mann, Kenneth A; Helms, Jill A; Castillo, Alesha B

    2018-03-01

    Mechanical loading is an important aspect of post-surgical fracture care. The timing of load application relative to the injury event may differentially regulate repair depending on the stage of healing. Here, we used a novel mechanobiological model of cortical defect repair that offers several advantages including its technical simplicity and spatially confined repair program, making effects of both physical and biological interventions more easily assessed. Using this model, we showed that daily loading (5N peak load, 2Hz, 60 cycles, 4 consecutive days) during hematoma consolidation and inflammation disrupted the injury site and activated cartilage formation on the periosteal surface adjacent to the defect. We also showed that daily loading during the matrix deposition phase enhanced both bone and cartilage formation at the defect site, while loading during the remodeling phase resulted in an enlarged woven bone regenerate. All loading regimens resulted in abundant cellular proliferation throughout the regenerate and fibrous tissue formation directly above the defect demonstrating that all phases of cortical defect healing are sensitive to physical stimulation. Stress was concentrated at the edges of the defect during exogenous loading, and finite element (FE)-modeled longitudinal strain (ε zz ) values along the anterior and posterior borders of the defect (~2200με) was an order of magnitude larger than strain values on the proximal and distal borders (~50-100με). It is concluded that loading during the early stages of repair may impede stabilization of the injury site important for early bone matrix deposition, whereas loading while matrix deposition and remodeling are ongoing may enhance stabilization through the formation of additional cartilage and bone. Published by Elsevier Inc.

  13. Modelling catchment management impact on in-stream phosphorus loads in northern Victoria.

    Science.gov (United States)

    Vigiak, O; Rattray, D; McInnes, J; Newham, L T H; Roberts, A M

    2012-11-15

    Phosphorus pollution severely impairs the water quality of rivers in Australia and worldwide. Conceptual models have proved useful to assess management impact on phosphorus loads, particularly in data-sparse environments. This paper develops and evaluates the coupling of a point-scale model (HowLeaky2008) to a catchment scale model (CatchMODS) to enhance modelling of farm management impacts on in-stream phosphorus loads. The model was tested in two adjacent catchments in northern Victoria (Avon-Richardson and Avoca), Australia. After calibration of the in-stream attenuation parameter against measurements at gauging stations, the model simulated specific annual phosphorus loads across the catchments well (Nash-Sutcliffe model efficiency of 0.52 in the Avon-Richardson and 0.83 for the Avoca catchment). Phosphorus loads at both catchment outlets under current conditions were estimated at 7 t y(-1) and were dominated by field exports. Changes to farm management practices, i.e. the use of perennial pastures in grazing systems and zero-tillage in cropping systems were estimated to reduce phosphorus load by 31% in the Avon-Richardson catchment and 19% in the Avoca catchment, relative to current practices (annual pasture and minimum tillage). The model afforded a major improvement in conceptual modelling by explicit simulation of the impacts of soil and climatic conditions on field-scale exports and by placing them in the context of landscape processes. Copyright © 2012 Elsevier Ltd. All rights reserved.

  14. Urban Saturated Power Load Analysis Based on a Novel Combined Forecasting Model

    Directory of Open Access Journals (Sweden)

    Huiru Zhao

    2015-03-01

    Full Text Available Analysis of urban saturated power loads is helpful to coordinate urban power grid construction and economic social development. There are two different kinds of forecasting models: the logistic curve model focuses on the growth law of the data itself, while the multi-dimensional forecasting model considers several influencing factors as the input variables. To improve forecasting performance, a novel combined forecasting model for saturated power load analysis was proposed in this paper, which combined the above two models. Meanwhile, the weights of these two models in the combined forecasting model were optimized by employing a fruit fly optimization algorithm. Using Hubei Province as the example, the effectiveness of the proposed combined forecasting model was verified, demonstrating a higher forecasting accuracy. The analysis result shows that the power load of Hubei Province will reach saturation in 2039, and the annual maximum power load will reach about 78,630 MW. The results obtained from this proposed hybrid urban saturated power load analysis model can serve as a reference for sustainable development for urban power grids, regional economies, and society at large.

  15. Dietary influences on nutrient partitioning and anatomical body composition of growing pigs; modelling and experimental approaches

    NARCIS (Netherlands)

    Halas, V.

    2004-01-01

    Prediction of pig performance from data on nutrient intake and animal properties makes it easier to obtain a better productivity. It provides tools to arrive at desired outputs, or to calculate required inputs. Thus it enables production to be flexible, safe and less erratic. It is to be expected

  16. Titanium dioxide nanoparticle ingestion alters nutrient absorption in an in vitro model of the small intestine

    Science.gov (United States)

    Ingestion of nanoparticles from products such as agricultural chemicals, processed food, and nutritional supplements is nearly unavoidable. The gastrointestinal tract serves as a critical interface and a barrier between the body and the external environment, and is the site of essential nutrient abs...

  17. Reactive transport modeling of biogeochemical dynamics in subterranean estuaries: Implications for submarine groundwater discharge of nutrients

    NARCIS (Netherlands)

    Spiteri, C.

    2007-01-01

    The quality of groundwater, in particular in coastal areas, is increasingly deteriorating due to the input of nutrients (NO3-, NH4+ and PO4) from septic systems and agricultural leaching. The discharge of groundwater to coastal waters, termed submarine groundwater discharge (SGD), is now recognized

  18. Nutrient budgets for large Chinese estuaries

    Directory of Open Access Journals (Sweden)

    S. M. Liu

    2009-10-01

    Full Text Available Chinese rivers deliver about 5–10% of global freshwater input and 15–20% of the global continental sediment to the world ocean. We report the riverine fluxes and concentrations of major nutrients (nitrogen, phosphorus, and silicon in the rivers of the contiguous landmass of China and Korea in the northeast Asia. The rivers are generally enriched with dissolved inorganic nitrogen (DIN and depleted in dissolved inorganic phosphate (PO43− with very high DIN: PO43− concentration ratios. DIN, phosphorus, and silicon levels and loads in rivers are mainly affected by agriculture activities and urbanization, anthropogenic activities and adsorption on particulates, and rock types, climate and physical denudation intensity, respectively. Nutrient transports by rivers in the summer are 3–4 times higher than those in the winter with the exception of NH4+. The flux of NH4+ is rather constant throughout the year due to the anthropogenic sources such as the sewer discharge. As nutrient composition has changed in the rivers, ecosystems in estuaries and coastal sea have also changed in recent decades. Among the changes, a shift of limiting nutrients from phosphorus to nitrogen for phytoplankton production with urbanization is noticeable and in some areas silicon becomes the limiting nutrient for diatom productivity. A simple steady-state mass-balance box model was employed to assess nutrient budgets in the estuaries. The major Chinese estuaries export <15% of nitrogen, <6% of phosphorus required for phytoplankton production and ~4% of silicon required for diatom growth in the Chinese Seas (Bohai, Yellow Sea, East China Sea, South China Sea. This suggests that land-derived nutrients are largely confined to the immediate estuaries, and ecosystem in the coastal sea beyond the estuaries is mainly supported by other nutrient sources such as regeneration, open ocean and

  19. Physics Based Model for Cryogenic Chilldown and Loading. Part I: Algorithm

    Science.gov (United States)

    Luchinsky, Dmitry G.; Smelyanskiy, Vadim N.; Brown, Barbara

    2014-01-01

    We report the progress in the development of the physics based model for cryogenic chilldown and loading. The chilldown and loading is model as fully separated non-equilibrium two-phase flow of cryogenic fluid thermally coupled to the pipe walls. The solution follow closely nearly-implicit and semi-implicit algorithms developed for autonomous control of thermal-hydraulic systems developed by Idaho National Laboratory. A special attention is paid to the treatment of instabilities. The model is applied to the analysis of chilldown in rapid loading system developed at NASA-Kennedy Space Center. The nontrivial characteristic feature of the analyzed chilldown regime is its active control by dump valves. The numerical predictions are in reasonable agreement with the experimental time traces. The obtained results pave the way to the development of autonomous loading operation on the ground and space.

  20. Thermodynamic parameters for mixtures of quartz under shock wave loading in views of the equilibrium model

    International Nuclear Information System (INIS)

    Maevskii, K. K.; Kinelovskii, S. A.

    2015-01-01

    The numerical results of modeling of shock wave loading of mixtures with the SiO 2 component are presented. The TEC (thermodynamic equilibrium component) model is employed to describe the behavior of solid and porous multicomponent mixtures and alloys under shock wave loading. State equations of a Mie–Grüneisen type are used to describe the behavior of condensed phases, taking into account the temperature dependence of the Grüneisen coefficient, gas in pores is one of the components of the environment. The model is based on the assumption that all components of the mixture under shock-wave loading are in thermodynamic equilibrium. The calculation results are compared with the experimental data derived by various authors. The behavior of the mixture containing components with a phase transition under high dynamic loads is described

  1. A Statistical Model for Natural Gas Standardized Load Profiles

    Czech Academy of Sciences Publication Activity Database

    Brabec, Marek; Konár, Ondřej; Malý, Marek; Pelikán, Emil; Vondráček, Jiří

    2009-01-01

    Roč. 58, č. 1 (2009), s. 123-139 ISSN 0035-9254 R&D Projects: GA AV ČR 1ET400300513 Institutional research plan: CEZ:AV0Z10300504 Keywords : disaggregation * generalized additive models * multiplicative model * non-linear effects * segmentation * semiparametric regression model Subject RIV: JE - Non-nuclear Energetics, Energy Consumption ; Use Impact factor: 1.060, year: 2009

  2. Modeling and Testing of Unbalanced Loading and Voltage Regulation

    Energy Technology Data Exchange (ETDEWEB)

    Davis, M. W.; Broadwater, R.; Hambrick, J.

    2007-07-01

    This report covers work to (1) develop and validate distribution circuit models, (2) determine optimum distributed generator operating conditions, and (3) determine distributed generation penetration limits.

  3. Comparison of Steady-State SVC Models in Load Flow Calculations

    DEFF Research Database (Denmark)

    Chen, Peiyuan; Chen, Zhe; Bak-Jensen, Birgitte

    2008-01-01

    This paper compares in a load flow calculation three existing steady-state models of static var compensator (SVC), i.e. the generator-fixed susceptance model, the total susceptance model and the firing angle model. The comparison is made in terms of the voltage at the SVC regulated bus, equivalent...... SVC susceptance at the fundamental frequency and the load flow convergence rate both when SVC is operating within and on the limits. The latter two models give inaccurate results of the equivalent SVC susceptance as compared to the generator model due to the assumption of constant voltage when the SVC...... of the calculated SVC susceptance while retaining acceptable load flow convergence rate....

  4. Cyclic loading of thick vessels based on the Prager and Armstrong-Frederick kinematic hardening models

    International Nuclear Information System (INIS)

    Mahbadi, H.; Eslami, M.R.

    2006-01-01

    The aim of this paper is to relate the type of stress category in cyclic loading to ratcheting or shakedown behaviour of the structure. The kinematic hardening theory of plasticity based on the Prager and Armstrong-Frederick models is used to evaluate the cyclic loading behaviour of thick spherical and cylindrical vessels under load and deformation controlled stresses. It is concluded that kinematic hardening based on the Prager model under load and deformation controlled conditions, excluding creep, results in shakedown or reversed plasticity for spherical and cylindrical vessels with the isotropy assumption of the tension/compression curve. Under an anisotropy assumption of the tension/compression curve, this model predicts ratcheting. On the other hand, the Armstrong-Frederick model predicts ratcheting under load controlled cyclic loading and reversed plasticity for deformation controlled stress. The interesting conclusion is that the Armstrong-Frederick model is well capable to predict the experimental data under the assumed type of stresses, wherever experimental data are available