5 Matching Results

Search Results

Advanced search parameters have been applied.

Enhancing the soil organic matter pool through biomass incorporation.

Description: A study was installed in the upper Coastal Plains of South Carolina, USA that sought to examine the impact of incorporating downed slash materials into subsoil layers on soil chemical and physical properties as compared with the effect of slash materials left on the soil surface. Two sites were examined which differed in soil textural composition: sandy vs. clay.
Date: January 1, 2003
Creator: Sanchez, Felipe G.; Carter, Emily A. & Klepac, John F.
Partner: UNT Libraries Government Documents Department

Effects of Microstructural Variables on the Shock Wave Response of PZT 95/5

Description: The particular lead zirconate/titanate composition PZT 95/5-2Nb was identified many years ago as a promising ferroelectric ceramic for use in shock-driven pulsed power supplies. The bulk density and the corresponding porous microstructure of this material can be varied by adding different types and quantities of organic pore formers prior to bisque firing and sintering. Early studies showed that the porous microstructure could have a significant effect on power supply performance, with only a relatively narrow range of densities providing acceptable shock wave response. However, relatively few studies were performed over the years to characterize the shock response of this material, yielding few insights on how microstructural features actually influence the constitutive mechanical, electrical, and phase-transition properties. The goal of the current work was to address these issues through comparative shock wave experiments on PZT 95/5-2Nb materials having different porous microstructures. A gas-gun facility was used to generate uniaxial-strain shock waves in test materials under carefully controlled impact conditions. Reverse-impact experiments were conducted to obtain basic Hugoniot data, and transmitted-wave experiments were conducted to examine both constitutive mechanical properties and shock-driven electrical currents. The present work benefited from a recent study in which a baseline material with a particular microstructure had been examined in detail. This study identified a complex mechanical behavior governed by anomalous compressibility and incomplete phase transformation at low shock amplitudes, and by a relatively slow yielding process at high shock amplitudes. Depoling currents are reduced at low shock stresses due to the incomplete transformation, and are reduced further in the presence of a strong electrical field. At high shock stresses, depoling currents are driven by a wave structure governed by the threshold for dynamic yielding. This wave structure is insensitive to the final wave amplitude, resulting in depoling currents that do not increase with shock amplitude for ...
Date: February 1, 2003
Creator: SETCHELL, ROBERT E.; TUTTLE, BRUCE A. & VOIGT, JAMES A.
Partner: UNT Libraries Government Documents Department

Enhancing the soil organic matter pool through biomass incorporation.

Description: A study was installed in the Upper Coastal Plain of South Carolina, USA, that sought to examine the impact of incorporating downed slash materials into subsoil layers on soil chemical and physical properties as compared with the effect of slash materials left on the soil surface. Baseline levels of slash were estimated by establishing transects within harvested stands and estimating the quantity of down wood and stumps. An equivalent quantity of biomass and two times the baseline levels were incorporated into subsurface soil layers by a CMI RS 500B reclaimer/stabilizer. Two sites were examined which differed in soil textural composition: sandy vs. clay. Site differences had no impact on machine productivity and machine costs were estimated at $US 521 ha-1 and $US 633 ha-1 on the ''sandy'' and ''clay'' sites, respectively. The feasibility of the CM1 for biomass incorporation is low due to high unit area costs but increased machine productivity would reduce costs and improve its potential. Biomass incorporation improved carbon and nutrient content of each site, especially on the sandy site. Slash levels had an impact on nutrient content but the differences were not statistically significant. For the sandy site, improvements in soil physical properties were evident in response to incorporation and machine planting operations. Bulk density and soil strength were reduced in response to biomass incorporation and tillage to levels that would not limit root production. The differences in soil physical response between incorporated treatments were minimal and not statistically significant.
Date: June 11, 2003
Creator: Sanchez, Felipe, G.; Carter, Emily, A. & Klepac, John, F.
Partner: UNT Libraries Government Documents Department

Quantification of Soil Physical Properties by Using X-Ray Computerized Tomography (CT) and Standard Laboratory (STD) Methods

Description: The implementation of x-ray computerized tomography (CT) on agricultural soils has been used in this research to quantify soil physical properties to be compared with standard laboratory (STD) methods. The overall research objective was to more accurately quantify soil physical properties for long-term management systems. Two field studies were conducted at Iowa State University's Northeast Research and Demonstration Farm near Nashua, IA using two different soil management strategies. The first field study was conducted in 1999 using continuous corn crop rotation for soil under chisel plow with no-till treatments. The second study was conducted in 2001 and on soybean crop rotation for the same soil but under chisel plow and no-till practices with wheel track and no-wheel track compaction treatments induced by a tractor-manure wagon. In addition, saturated hydraulic (K{sub s}) conductivity and the convection-dispersion (CDE) model were also applied using long-term soil management systems only during 2001. The results obtained for the 1999 field study revealed no significant differences between treatments and laboratory methods, but significant differences were found at deeper depths of the soil column for tillage treatments. The results for standard laboratory procedure versus CT method showed significant differences at deeper depths for the chisel plow treatment and at the second lower depth for no-till treatment for both laboratory methods. The macroporosity distribution experiment showed significant differences at the two lower depths between tillage practices. Bulk density and percent porosity had significant differences at the two lower depths of the soil column. The results obtained for the 2001 field study showed no significant differences between tillage practices and compaction practices for both laboratory methods, but significant differences between tillage practices with wheel track and no-wheel compaction treatments were found along the soil profile for both laboratory methods. The K{sub s} measurements and CDE parameters revealed no significant ...
Date: December 12, 2003
Creator: Sanchez, Maria Ambert
Partner: UNT Libraries Government Documents Department

CARBON SEQUESTRATION ON SURFACE MINE LANDS

Description: The 2002-2003 Department of Energy plantings amounted to 164 acres containing 111,520 tree seedlings in eastern and western Kentucky. Data gathered on these trees included an inventory to determine survival of all planted species. A sub-sample of seedlings was selected to assess the height and diameter of individual species of seedlings established. Additional efforts involved collection of soil sample and litter samples, analysis of herbaceous ground cover from vegetation clip plots and leaf area on each tree species, and development of tissue collections. All areas were sampled for penetration resistance, penetration depth (or depth to refusal), and bulk density at various depths. Rain fall events and flow rates were recorded. The water quality of runoff samples involved the determination of total and settleable solids and particle size distribution. A study was initiated that will focus on the colonization of small mammals from forest edges to various areas located on reclaimed surface mines. This effort will provide a better understanding of the role small mammals and birds have in the establishment of plant communities on mine lands that will be useful in developing and improving reclamation techniques.
Date: October 30, 2003
Creator: Graves, Donald H.; Barton, Christopher; Sweigard, Richard & Warner, Richard
Partner: UNT Libraries Government Documents Department