1,045 Matching Results

Search Results

Advanced search parameters have been applied.

The Precipitation of Strontium Sulfate in Gels

Description: The growth of strontium sulfate precipitate by diffusion in various gels was studied by using optical transmission and confocal microscopies, scanning and transmission electron microscopies, and energy dispersive X ray fluorescence. Pure silica gel, pure agarose gel and the silica/agarose mixed gel at pH 7 - 10 were used throughout the present study. Precipitate morphology is sensitive to pH and to the nature of the growth medium. The morphology was observed as a function of time. The lack of change is presumably because of rapid depletion of the limiting reagent after the very beginning of precipitation. The problem of separating strontium sulfate precipitate from the gel medium is discussed.
Date: December 1991
Creator: Lee, Ya
Partner: UNT Libraries

Precipitation-Runoff Modeling System: User's Manual

Description: From introduction: This documentation is designed to provide the user with the basic philosophy and structure of PRMS, instructions for application of established models designed as cataloged procedures, and instructions for interaction with the PRMS library to permit user additions or modifications of model components. The components and subroutines described in this document are those available at the time of publication. However, the library is dynamic and will be enhanced and updated through time. This manual will be updated to reflect major additions and changes through manual inserts or republications.
Date: 1983
Creator: Leavesley, G. H.; Lichty, R. W.; Troutman, B. M. & Saindon, L. G.
Partner: UNT Libraries Government Documents Department

Precipitation and Pattern Formation under Far-From-Equilibrium Conditions

Description: Precipitates of a series of alkaline earth metal (barium and strontium) carbonates, chromates, phosphates, and sulfates were formed at high supersaturation by diffusion through silica hydrogel, agarose hydrogel, and the freshly developed agarosesilica mixed gels. The reaction vessels could be a small test tube, a recently designed standard micro slide cassette and a enlarged supercassette. Homogeneous nucleation is thought to have taken place, and particle development led to the formation of an unusual category of materials, known as Induced Morphology Crystal Aggregates [IMCA], at high pH under far-from-equilibrium conditions. Standard procedures were developed in order to produce homogeneous gels. Particle development led to characteristic style of pattern formation, which I have called monster, spiral, and flake. Among these IMCA, barium carbonate, chromate, and sulfate were moderately easy to grow. Barium phosphate was very difficult to grow as IMCA due to formation of poorly crystalline spherulites. IMCA of strontium carbonate, chromate and sulfate could be developed at high basic pH in the presence of silicate. Strontium carbonate sheet morphology displays a unique property, double internal layer structure, which was identified by backscattering electron imaging (BEI). Selected electron diffraction (SAD) revealed a new crystal phase which was called "Dentonite". Precipitate particles were isolated using a non-destructive isolation technique. Optical microscopy was widely used to examine particles in situ and scanning electron microscopy and X-ray dispersive energy (EDX) spectroscopy were applied to particles ex situ, together with ESCA for surface analysis. Growth patterns were found to be strongly dependent on pH. Other related pattern formation processes were also investigated including normal and dendritic structures, spherulitic structures and periodic pattern formation. Some interpretations were proposed in terms of mechanism. Chemical additive effects were examined experimentally in the calcium phosphate system. The effect of external ionic strength was investigated, and it was found that a ...
Date: August 1995
Creator: Chen, Peng, 1960-
Partner: UNT Libraries

The Adsorption of Radioactive Isotopes on Precipitates

Description: This thesis concerns the investigation of radioisotopes as indicators for precipitation reactions. As a precipitate forms in the presence of a radioisotope, adsorption may take place on its surface. If this adsorption changes markedly at the stoichiometric point it will be possible to use this variation as an indicator for the reaction.
Date: January 1954
Creator: Bulloch, Newman Payne
Partner: UNT Libraries

Studies Regarding the Role of Wyoming Natural Gas in Precipitating Primary uranium Minerals from Pregnant Solutions

Description: Abstract: This project was designed to test the chemical feasibility of depositing of depositing a primary uranium mineral from a pregnant solution by exposing the solution to natural gas in an environment favorable to such deposition.
Date: May 11, 1956
Creator: Sims, Harry M. & Smith, Fred L.
Partner: UNT Libraries Government Documents Department

Interannual Variations in Simulated and Observed MSU-2 Temperatures

Description: Microwave Sounding Unit (MSU) channel 2 temperatures are computed for three sets of model experiments and their interannual variation is compared to that of the observed. The models used are: (1) an ensemble of ten integrations of the NCAR CCM3 using prescribed SSTs for 1979 t o 1995, (2) A 300 year integration of the NCAR/DOE Parallel Climate Model (which has the CCM3 as the atmospheric model) and (3) a 300 year integration of the ECHAM4/OPYC coupled model at the Max Planck Institute for Meteorology. In addition Nino34 and AO indices were computed from SST and MSLP of each data set. The observed data spanned the period of 1979 to 1998. The CCM3 integrations used the observed SSTs from 1979 to 1995. The 300 year coupled runs were divided into non-overlapping 20 year segments and each segment was processed independently. The EOFs of the zonally averaged, monthly mean MSU-2 anomalies were computed. An SVD analysis of the covariance of the tropical (30S-30N) precipitation and MSU-2 was carried out. The first and second mode of the observations are related to the ENSO variations and the Arctic Oscillation, respectively. The Nino34 index leads the ENSO mode by 5 months in the observations. For the nine realizations of the CCM3, all have the ENSO as the leading mode but one does not have the AO as the second. The lag between the Nino34 and leading EOF decreases to about 3 months.The fourteen PCM 20 year segments show a similar variation to the CCM3, but the lag is decreased to 2 months. All fourteen of the ECHAM segments have the ENSO and AO as the leading and second modes. The fourteen ECHAM data sets evince smaller variations between segments than the PCM and even the CCM3 realizations. The lag between the ECHAM Nino34 and ...
Date: August 16, 2000
Creator: Boyle, J.
Partner: UNT Libraries Government Documents Department

An Integrated Hydrologic Bayesian Multi-Model Combination Framework: Confronting Input, parameter and model structural uncertainty in Hydrologic Prediction

Description: This paper presents a new technique--Integrated Bayesian Uncertainty Estimator (IBUNE) to account for the major uncertainties of hydrologic rainfall-runoff predictions explicitly. The uncertainties from the input (forcing) data--mainly the precipitation observations and from the model parameters are reduced through a Monte Carlo Markov Chain (MCMC) scheme named Shuffled Complex Evolution Metropolis (SCEM) algorithm which has been extended to include a precipitation error model. Afterwards, the Bayesian Model Averaging (BMA) scheme is employed to further improve the prediction skill and uncertainty estimation using multiple model output. A series of case studies using three rainfall-runoff models to predict the streamflow in the Leaf River basin, Mississippi are used to examine the necessity and usefulness of this technique. The results suggests that ignoring either input forcings error or model structural uncertainty will lead to unrealistic model simulations and their associated uncertainty bounds which does not consistently capture and represent the real-world behavior of the watershed.
Date: May 5, 2006
Creator: Ajami, N K; Duan, Q & Sorooshian, S
Partner: UNT Libraries Government Documents Department

Climate system studies: final report to the U.S. Department of Energy

Description: In this final report, we summarize research on climate variability and forcing mechanisms responsible for these changes. We report on research related to high elevation climate change, changes in the hydrological cycle and the seasonality of precipitation and on changes in climatic extremes. A comprehensive bibliography of research articles and books arising from this grant is included as an appendix.
Date: March 1, 2000
Creator: Bradley, Raymond S. & Diaz, Henry F.
Partner: UNT Libraries Government Documents Department

Floods in New York, 1972, with Special Reference to Tropical Storm Agnes

Description: From introduction: Flooding and flood damage in New York during the calendar year 1972 are summarized in this report. The report was prepared at the request of the New York State Department of Transportation under provisions of an agreement between the department and the U.S. Geological Survey for a cooperative, statewide program to investigate the water resources of the State.
Date: January 1976
Creator: Robison, F. Luman
Partner: UNT Libraries Government Documents Department

Study of Substituted Benzenesulfonate-Containing Layered Double Hydroxides and Investigation of the Hexamethylenetetramine Route of LDH Synthesis

Description: Benzenesulfonates, para-substituted with amine, chloride and methyl groups were successfully incorporated into layered double hydroxides of two different compositions, 2:1 Mg-Al LDH and 2:1 Zn-Al LDH. These parent materials were also doped with small amounts of nickel and the differences in the two systems were studied. The hexamethylenetetramine route of layered double hydroxide synthesis was investigated to verify if the mechanism is indeed homogeneous. This included attempting preparation of 2:1 Mg-Al LDH, 2:1 Zn-Al LDH and 2:1 Zn-Cr LDH with two different concentrations of hexamethylenetetramine. The analytical data of the products suggest that the homogeneous precipitation may not be the true mechanism of reaction involved in LDH synthesis by this method.
Date: May 2007
Creator: Ambadapadi, Sriram
Partner: UNT Libraries

2.1 Pan-WCRP Monsoon Modelling Workshop Summary

Description: Ken Sperber led a discussion of the outcome of the Pan-WCRP Monsoon Modelling Workshop that was held at the University of California at Irvine from 15-17 June 2005. At the workshop presentations from key CLIVAR and GEWEX panels were presented to highlight the outstanding problems in modelling the Earth's monsoons. Additionally, presentations from invited experts were given to highlight important aspects of monsoon phenomena and processes, such as low-level jets, air-sea interaction, predictability, observational networks/studies, and model test beds etc. Since all persons attending the CLIVAR AAMP meeting were present for all, or most, of the monsoon workshop, a detailed description of the workshop presentations was not given. Rather, the discussion was focused on the recommendations of the workshop breakout groups and their relevance to CLIVAR AAMP. CLIVAR AAMP endorsed the near-term workshop recommendation of investigating the diurnal cycle using a hierarchy of models a key way forward for promoting CLIVAR/GEWEX interactions. In GCM studies CLIVAR researchers have identified the diurnal cycle as a forced ''mode'' of variability that is poorly represented in terms of amplitude and phase, especially in the case of precipitation. Typical phase errors of 6-12 hours are noted over both land and ocean in GCMs. CLIVAR views adequate simulation of the diurnal cycle as key aspect of variability in its own right, but also because of its potential rectification on to subseasonal variability (e.g., the Madden-Julian oscillation). It is hypothesized that improvement of diurnal variability may lead to an improved representation of intraseasonal variability and improved skill of monsoon forecasts on medium-range to seasonal time scales.
Date: June 28, 2005
Creator: Sperber, K R
Partner: UNT Libraries Government Documents Department

Evaluation of Continental Precipitation in 20th-Century Climate Simulations: The Utility of Multi-Model Statistics

Description: At the request of the Intergovernmental Panel on Climate Change (IPCC), simulations of 20th-century climate have been performed recently with some 20 global coupled ocean-atmosphere models. In view of its central importance for biological and socio-economic systems, model-simulated continental precipitation is evaluated relative to three observational estimates at both global and regional scales. Many models are found to display systematic biases, deviating markedly from the observed spatial variability and amplitude/phase of the seasonal cycle. However, the point-wise ensemble mean of all the models usually shows better statistical agreement with the observations than does any single model. Deficiencies of current models that may be responsible for the simulated precipitation biases as well as possible reasons for the improved estimate afforded by the multi-model ensemble mean are discussed. Implications of these results for water-resource managers also are briefly addressed.
Date: November 1, 2005
Creator: Phillips, T. J. & Gleckler, P. J.
Partner: UNT Libraries Government Documents Department

Establishment of an NWP testbed using ARM data

Description: The aim of the FAst-physics System TEstbed and Research (FASTER) project is to evaluate and improve the parameterizations of fast physics (involving clouds, precipitation, aerosol) in numerical models using ARM measurements. One objective within FASTER is to evaluate model representations of fast physics with long-term continuous cloud observations by use of an 'NWP testbed'. This approach was successful in the European Cloudnet project. NWP model data (NCEP, ECMWF, etc.) is routinely output at ARM sites, and model evaluation can potentially be achieved in quasi-real time. In this poster, we will outline our progress in the development of the NWP testbed and discuss the successful integration of ARM algorithms, such as ARSCL, with algorithms and lessons learned from Cloudnet. Preliminary results will be presented of the evaluation of the ECMWF, NCEP, and UK Met Office models over the SGP site using this approach.
Date: March 15, 2010
Creator: O'Connor, E.; Liu, Y. & Hogan, R.
Partner: UNT Libraries Government Documents Department

A study of cloud and drizzle properties in the Azores using Doppler Radar spectra

Description: Understanding the onset of coalescence in warm clouds is key in our effort to improve cloud representation in numerical models. Coalescence acts at small scales, and its study requires detailed high-resolution dynamical and microphysical measurements from a comprehensive suite of instruments over a wide range of environmental conditions (e.g., aerosol loading). The first AMF is currently in its second year of a two-year deployment at Graciosa Island in the Azores, offering the opportunity to collect a long data set from a stable land-based platform in a marine stratocumulus regime. In this study, recorded WACR Doppler spectra are used to characterize the properties of Doppler spectra from warm clouds with and without drizzle, and from drizzle only, in an effort to observe the transition (onset) to precipitation in clouds. A retrieval technique that decomposes observed Doppler spectra into their cloud and/or drizzle components is applied in order to quantify drizzle growth.
Date: March 15, 2010
Creator: Luke, E.; Remillard, J. & Kollias, P.
Partner: UNT Libraries Government Documents Department

Sediment Discharge from an Area of Highway Construction, Applemans Run Basin, Columbia County, Pennsylvannia

Description: Report and Geographical Survey. Includes and introduction, data collection, basin description, highway construction, suspended-sediment discharge, information on the flood of June 1972, and a summary with conclusions. Also includes several graphs and tables.
Date: October 1976
Creator: Eckhardt, David A. V.
Partner: UNT Libraries Government Documents Department


Description: Recent data sets for three meteorological phenomena with the potential to inflict damage on SRS facilities - tornadoes, straight winds, and heavy precipitation - are analyzed using appropriate statistical techniques to estimate occurrence probabilities for these events in the future. Summaries of the results for DOE-mandated return periods and comparisons to similar calculations performed in 1998 by Weber, et al., are given. Using tornado statistics for the states of Georgia and South Carolina, we calculated the probability per year of any location within a 2⁰ square area surrounding SRS being struck by a tornado (the ‘strike’ probability) and the probability that any point will experience winds above set thresholds. The strike probability was calculated to be 1.15E-3 (1 chance in 870) per year and wind speeds for DOE mandated return periods of 50,000 years, 125,000 years, and 1E+7 years (USDOE, 2012) were estimated to be 136 mph, 151 mph and 221 mph, respectively. In 1998 the strike probability for SRS was estimated to be 3.53 E-4 and the return period wind speeds were 148 mph every 50,000 years and 180 mph every 125,000 years. A 1E+7 year tornado wind speed was not calculated in 1998; however a 3E+6 year wind speed was 260 mph. The lower wind speeds resulting from this most recent analysis are largely due to new data since 1998, and to a lesser degree differences in the models used. By contrast, default tornado wind speeds taken from ANSI/ANS-2.3-2011 are somewhat higher: 161 mph for return periods of 50,000 years, 173 mph every 125,000 years, and 230 mph every 1E+7 years (ANS, 2011). Although the ANS model and the SRS models are very similar, the region defined in ANS 2.3 that encompasses the SRS also includes areas of the Great Plains and lower Midwest, regions with much higher ...
Date: December 4, 2013
Creator: Werth, D.; Weber, A. & Shine, G.
Partner: UNT Libraries Government Documents Department

Performance of Evapotranspirative Covers Under Enhanced Precipitation: Preliminary Data

Description: Since January 2001, drainage lysimeter studies have been conducted at Yucca Flat, on the Nevada Test Site, in support of an evapotranspirative cover design. Yucca Flat has an arid climate with average precipitation of 16.5 cm annually. The facility consists of six drainage lysimeters 3 m in diameter, 2.4 m deep, and backfilled with a single layer of native soil. The bottom of each lysimeter is sealed and equipped with a small drain that enables direct measurement of saturated drainage. Each lysimeter has eight time-domain reflectometer probes to measure moisture content-depth profiles paired with eight heat-dissipation probes to measure soil-water potential depth profiles. Sensors are connected to dataloggers which are remotely accessed via a phone line. The six lysimeters have three different surface treatments: two are bare-soil; two were revegetated with native species (primarily shadscale, winterfat, ephedra, and Indian rice grass); and two were allowed to revegetate naturally with such species as Russian thistle, halogeton, tumblemustard and cheatgrass. Beginning in October 2003, one half of the paired cover treatments (one bare soil, one invader species, and one native species) were irrigated with an amount of water equal to two times the natural precipitation to achieve a three times natural precipitation treatment. From October 2003 through December 2005, all lysimeters received 52.8 cm precipitation, and the four irrigated lysimeters received an extra 105.6 cm of irrigation. No drainage has occurred from any of the nonirrigated lysimeters, but moisture has accumulated at the bottom of the bare-soil lysimeter and the native-plant lysimeter. All irrigated lysimeters had some drainage. The irrigated baresoil lysimeter had 48.3 cm of drainage or 26.4 percent of the combined precipitation and applied irrigation for the entire monitoring record. The irrigated invader species lysimeter had 5.8 cm of drainage, about 3.2 percent of the combined precipitation and applied irrigation. ...
Date: February 1, 2007
Creator: David C. Anderson, Lloyd T. Desotell, David B. Hudson, Gregory J. Shott, Vefa Yucel
Partner: UNT Libraries Government Documents Department

Upscaling of Bio-mediated Soil Improvement

Description: As demand for soil improvement continues to increase, new, sustainable, and innocuous methods are needed to alter the mechanical properties of soils. Recent research has demonstrated the potential of bio-mediated soil improvement for geotechnical applications (DeJong et al. 2006, Whiffin et al. 2007). Upscaling the bio-mediated treatment process for in situ implementation presents a number of challenges to be addressed, including soil and pore fluid interactions, bioaugmentation versus biostimulation of microbial communities, controlled distribution of mediated calcite precipitation, and permanence of the cementation. Current studies are utilizing large-scale laboratory experiments, non-destructive geophysical measurements, and modeling, to develop an optimized and predictable bio-mediated treatment method.
Date: October 1, 2009
Creator: DeJong, J. T.; Martinez, B. C.; Mortensen, B. M.; Nelson, D. C.; Waller, J. T.; Weil, M. H. et al.
Partner: UNT Libraries Government Documents Department

Analysis of Copper in the In-Tank Precipitation Process Caustic Samples

Description: Inductively Coupled Plasma Emission Spectroscopy (ICPES) and Inductively Coupled Plasma Mass Spectrometry (ICPMS) procedures for measuring Cu in In-Tank Precipitation (ITP) caustic samples have been tested and implemented in the Analytical Development Section at the Savannah River Technology Center.
Date: December 12, 1996
Creator: Tovo, L.L. & Boyce, W.T.
Partner: UNT Libraries Government Documents Department

Predicted 21st century changes in seasonal extreme precipitation events in the parallel climate model

Description: Twenty-year return value of annual and seasonal maxima of daily precipitation are calculated from a set of transiently forced coupled general circulation model simulations. The magnitude and pattern of return values are found to be highly dependent on the seasonal cycle. A similar dependence is found for projected future changes in return values. The correlation between the spatial pattern of return value changes and mean precipitation changes is found to be low. Hence, the changes in mean precipitation do not provide significant information about changes in precipitation extreme values.
Date: June 7, 2004
Creator: Wehner, Michael F.
Partner: UNT Libraries Government Documents Department