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Application of US upper wind data in one design of tethered wind energy systems

Description: The upper atmospheric wind resource for the continental United States, Hawaii, and Alaska is assessed. The raw data were obtained from the National Center for Atmospheric Research, Boulder, Colo. The probability distributions of velocity are presented for 54 sites, and detailed calm wind analyses have been undertaken for five of these locations. On the average, the wind lulls about one day per week for a period in excess of about 30 hours. It is shown that the average power density of this wind resource can be as high as 16 kW/m/sup 2/ at northeastern US sites. This power density is at a maximum around the 300-mb pressure level.
Date: February 1, 1982
Creator: O'Doherty, R.J. & Roberts, B.W.
Partner: UNT Libraries Government Documents Department

Spectral induced polarization signatures of abiotic FeS precipitation

Description: In recent years, geophysical methods have been shown to be sensitive to microbial induced mineralization processes. The spectral induced polarization (SIP) method appears to be very promising for monitoring mineralization and microbial processes. With this work, we study the links of mineralization and SIP signals, in the absence of microbial activity. We recorded the SIP response during abiotic FeS precipitation. We show that the SIP signals are diagnostic of FeS mineralization and can be differentiated from SIP signals from bio-mineralization processes. More specifically the imaginary conductivity shows almost linear dependence on the amount of FeS precipitating out of solution, above the threshold value 0.006 gr under our experimental conditions. This research has direct implications for the use of the SIP method as a monitoring, and decision making, tool for sustainable remediation of metals in contaminated soils and groundwater.
Date: January 15, 2010
Creator: Ntarlagiannis, D.; Doherty, R. & Williams, K. H.
Partner: UNT Libraries Government Documents Department

Structural evolution during recrystallization

Description: The evidence showing the failure of the classic Johnson-Mehl-Avrami equation to describe most recrystallization kinetics is reviewed. The failure is seen in the value of the exponent n which is much less than the theoretically predicted exponents. The reason for this failure is at least in part due to the nonrandom distribution of nucleation sites. This nonrandom distribution seems to arise from the grain to grain variation in deformation microstructure. Simple 3-dimensional and more precise 2-dimensional models of the recrystallization kinetics are presented which demonstrate that variation in the stored energy, on the scale of the grain size, does lead to the range of JMA exponents seen experimentally. The importance of this for the resulting grain size distributions is indicated.
Date: January 1, 1986
Creator: Doherty, R.D.; Rollett, A.R. & Srolovitz, D.J.
Partner: UNT Libraries Government Documents Department

Stage IV work hardening in cubic metals

Description: The work hardening of fcc metals at large strains is discussed with reference to the linear stress-strain behavior often observed at large strains and known as Stage IV. The experimental evidence shows that Stage IV is a work hardening phenomenon that is found quite generally, even in pure fcc metals subjected to homogeneous deformation. A simple model for Stage IV in pure metals is presented, based on the accumulation of dislocation debris. Experiments are described for large strain torsion tests on four aluminum alloys. The level and extent of Stage IV scaled with the saturation stress that would represent the end of Stage III in the absence of a Stage IV. Reversing the torsion after large prestrains produced transient reductions in the work hardening. The strain rate sensitivity was also measured before and during the transient and found not to vary significantly. The microstructure observed at large strains in an Mg alloy suggest that Stage IV can occur in the absence of microband formation. Previous proposals for the cause of Stage IV are reviewed and found to be not supported by recent experimental data.
Date: January 1, 1986
Creator: Rollett, A.D.; Kocks, U.F. & Doherty, R.D.
Partner: UNT Libraries Government Documents Department

The development of cube and non-cube recrystallization textures

Description: The development of recrystallization textures in cold rolled copper has been characterized using an electron backscatter pattern (EBSP) technique. Cube oriented grains exist in materials that have been annealed after a series of rolling strains, between 1.0 and 4.5 (von Mises strain). The strength and sharpness of these cube textures increases with increasing strain thus replacing the random texture produced by recrystallization of moderately deformed copper. The preferential formation of the cube, texture is attributed to the homogenization of stored energy gradients adjacent to randomly oriented nucleation sites. This process, coupled with the development of the microstructure adjacent to deformed cube sites, favors nucleation and growth of cube grains over randomly oriented grains.
Date: July 1, 1995
Creator: Necker, C.T.; Rollett, A.D. & Doherty, R.D.
Partner: UNT Libraries Government Documents Department

Comparative Study of Four Passive Building Energy Simulations DOE 2.1, BLAST, SUNCAT 2.4, DEROB-III

Description: Four building energy analysis codes are compared using two direct gain building models with Madison TMY weather data. Hourly temperature profiles and annual heating and cooling loads are compared and discussed. An analytic verification technique is described and used to investigate performance of the four codes. An anomaly is discovered in one of the codes, and the analytic verification technique is used to test a modified version of this code.
Date: October 1, 1980
Creator: Judkoff, R.; Wortman, D.; Christensen, C.; O'Doherty, R.; Simms, D. & Hannifan, M.
Partner: UNT Libraries Government Documents Department

Development of recrystallization texture and microstructure in cold rolled copper

Description: Oxygen free electronic copper, 99.995% purity, of two initial grain sizes, 50 {mu}m and 100 {mu}m, has been cold rolled to six strains of 1.0, 1.5, 2.0, 2.65, 3.5 and 4.5 (von Mises equivalents). The rolled materials were partially and fully recrystallized to study the development of recrystallization textures as a function of grain size, strain and fraction recrystallized. The initial textures were relatively random and the deformation textures show the classic {beta} fiber development. As strain is increased both materials produce increasingly intense cube recrystallization textures, (100)<001>, as measured both by x-ray diffraction and the electron backscatter pattern (EBSP) techniques. The strong cube recrystallization textures are a product of a higher than random frequency of cube nucleation sites. An additional factor is that cube regions grow larger than non-cube regions. The explanation of the cube frequency advantage is based on the development of large stored energy differences between cube orientations and neighboring orientations due to recovery of cube sites. Of several possible explanations of the cube orientation size advantage, the most plausible one is solute entrapment. At the higher strains the boundaries of cube grains encounter the deformation texture S components, (123)<634>, changing the boundary character to one of 40{degrees}<111>. These boundaries are more resistant to solute accumulation than random high angle boundaries, allowing the boundaries to migrate with less of a solute drag effect than a random high angle boundary.
Date: December 31, 1996
Creator: Necker, C.T.; Doherty, R.D. & Rollett, A.D.
Partner: UNT Libraries Government Documents Department

Computer modelling of particle limited grain growth and its experimental verification

Description: Data from two simulations on particle limited grain growth are reported. For 3D simulations the same type of strong correlation between particles and grain boundaries previously found in 2D simulations was found with the limiting grain size scaling in 3D with (l/f){sup 0.31}. Very much higher particle correlation with grain boundaries and particularly with grain corners was obtained than expected for the random microstructure. The size distribution of the pinned grain structures showed considerable differences from that of dynamically evolving single phase structures -- notably an absence of small grains with radii less than 0.3 <R> and the presence of a few large grains in the pinned samples. In 2D simulations from a finite starting grain size which may explain at least part of the wide scatter in pinned grain sizes reported from experimental studies. It is suggested that normal grain growth ceases when the smallest grains in the size distribution can no longer shrink. Finally limited new experimental data on grain growth with a stable dispersion in an Al-Fe alloy is reported. This data is, at least partially, in agreement with the simulation results but most strikingly shows a ready transition to abnormal grain growth at low volume fraction of second phase particles. A simple model for this effect is proposed -- based on the Zener analysis but applied only to abnormal grain growth into a fine grain structure pinned to a small grain size in the manner suggested by the simulations. 39 refs., 14 figs., 5 tabs.
Date: January 1, 1989
Creator: Doherty, R.D.; Li, K.; Kashyup, K.; Rollett, A.D. & Anderson, M.P.
Partner: UNT Libraries Government Documents Department

Core Drilling at Shaft Sites of Proposed Mine-Water Drainage Tunnel: Anthracite Region of Pennsylvania

Description: From Scope of Report: "This report deals with the diamond drilling of 15 holes at the shaft of the proposed main drainage tunnel and with the information obtained by a petrographic examination of the core drillings from these boreholes.
Date: 1952
Creator: Ash, S. H. (Simon Harry), b. 1889; Doherty, R. Emmet; Miller, P. S.; Romischer, W. M. & Smith, J. D.
Partner: UNT Libraries Government Documents Department

Quantitative measurement of the development of recrystallization texture in OFE copper

Description: High purity OFE copper samples, cold rolled 58, 73 and 90%, were studied at different fractions recrystallized to follow the change of texture, the associated kinetics, release of stored energy, growth rates and microstructures. Higher strains led to a stronger copper deformation component and a stronger cube recrystallization component. The strength of the cube texture correlated strongly with the frequency of cube nuclei at the early stage of recrystallization for the 73 and 90% reductions. The kinetics had low Avrami exponents of 1.1, 1.2 and 1.8 respectively for the 3 rolling reductions. Average growth rates, G, decreased linearly with fraction recrystallized. However, unlike the study by Hutchinson et al., here the rate of stored energy release was constant with fraction recrystallized. 14 refs., 5 figs.
Date: January 1, 1990
Creator: Necker, C.T.; Doherty, R.D. (Drexel Univ., Philadelphia, PA (USA). Dept. of Materials Engineering) & Rollett, A.D. (Los Alamos National Lab., NM (USA))
Partner: UNT Libraries Government Documents Department

A multi-model assessment of pollution transport to the Arctic

Description: We examine the response of Arctic gas and aerosol concentrations to perturbations in pollutant emissions from Europe, East and South Asia, and North America using results from a coordinated model intercomparison. These sensitivities to regional emissions (mixing ratio change per unit emission) vary widely across models and species. Intermodel differences are systematic, however, so that the relative importance of different regions is robust. North America contributes the most to Arctic ozone pollution. For aerosols and CO, European emissions dominate at the Arctic surface but East Asian emissions become progressively more important with altitude, and are dominant in the upper troposphere. Sensitivities show strong seasonality: surface sensitivities typically maximize during boreal winter for European and during spring for East Asian and North American emissions. Mid-tropospheric sensitivities, however, nearly always maximize during spring or summer for all regions. Deposition of black carbon (BC) onto Greenland is most sensitive to North American emissions. North America and Europe each contribute {approx}40% of total BC deposition to Greenland, with {approx}20% from East Asia. Elsewhere in the Arctic, both sensitivity and total BC deposition are dominated by European emissions. Model diversity for aerosols is especially large, resulting primarily from differences in aerosol physical and chemical processing (including removal). Comparison of modeled aerosol concentrations with observations indicates problems in the models, and perhaps, interpretation of the measurements. For gas phase pollutants such as CO and O{sub 3}, which are relatively well-simulated, the processes contributing most to uncertainties depend on the source region and altitude examined. Uncertainties in the Arctic surface CO response to emissions perturbations are dominated by emissions for East Asian sources, while uncertainties in transport, emissions, and oxidation are comparable for European and North American sources. At higher levels, model-to-model variations in transport and oxidation are most important. Differences in photochemistry appear to play the ...
Date: March 13, 2008
Creator: Shindell, D T; Chin, M; Dentener, F; Doherty, R M; Faluvegi, G; Fiore, A M et al.
Partner: UNT Libraries Government Documents Department

The Global Atmospheric Environment for the Next Generation

Description: Air quality, ecosystem exposure to nitrogen deposition, and climate change are intimately coupled problems: we assess changes in the global atmospheric environment between 2000 and 2030 using twenty-five state-of-the-art global atmospheric chemistry models and three different emissions scenarios. The first (CLE) scenario reflects implementation of current air quality legislation around the world, whilst the second (MFR) represents a more optimistic case in which all currently feasible technologies are applied to achieve maximum emission reductions. We contrast these scenarios with the more pessimistic IPCC SRES A2 scenario. Ensemble simulations for the year 2000 are consistent among models, and show a reasonable agreement with surface ozone, wet deposition and NO{sub 2} satellite observations. Large parts of the world are currently exposed to high ozone concentrations, and high depositions of nitrogen to ecosystems. By 2030, global surface ozone is calculated to increase globally by 1.5 {+-} 1.2 ppbv (CLE), and 4.3 {+-} 2.2 ppbv (A2). Only the progressive MFR scenario will reduce ozone by -2.3 {+-} 1.1 ppbv. The CLE and A2 scenarios project further increases in nitrogen critical loads, with particularly large impacts in Asia where nitrogen emissions and deposition are forecast to increase by a factor of 1.4 (CLE) to 2 (A2). Climate change may modify surface ozone by -0.8 {+-} 0.6 ppbv, with larger decreases over sea than over land. This study shows the importance of enforcing current worldwide air quality legislation, and the major benefits of going further. Non-attainment of these air quality policy objectives, such as expressed by the SRES-A2 scenario, would further degrade the global atmospheric environment.
Date: December 7, 2005
Creator: Dentener, F; Stevenson, D; Ellingsen, K; van Joije, T; Schultz, M; Amann, M et al.
Partner: UNT Libraries Government Documents Department