151 Matching Results

Search Results

Advanced search parameters have been applied.

The North Carolina School of Science and Mathematics

Description: Article by Charles R. Eilber detailing the North Carolina School of Science and Mathematics. He talks about the students, the instructional program, the residential program, support services, public services, the outcomes and costs, and the implications for education.
Date: June 1987
Creator: Eilber, Charles R.
Partner: Texas Academy of Mathematics and Science

Use of Municipal Sewage Sludge for Improvement of Forest Sites in the Southeast

Description: In eight field experiments dried municipal sewage sludge was applied to forest sites before planting of seedlings. In all cases, tree growth was faster on sludge-amended plots than on plots that received fertilizer and lime or no amendment. In all studies, concentrations of total nitrogen in the soil were higher on sludge plots than on control or fertilizer plots, even on good forest sites. In seven of the eight studies, concentrations of phosphorus also were higher on sludge plots than on control or fertilizer plots. Nitrogen and phosphorus tended to be higher in foliage from trees growing on sludge plots. Deep subsoiling was beneficial regardless of soil amendment. Where weeds were plentiful at the outset, they became serious competitors on plots receiving sludge.
Date: September 1987
Creator: Berry, Charles R.
Partner: UNT Libraries Government Documents Department

Experimental geothermal loop: I, 295/sup 0/C study

Description: Reaction of granodiorite from the Fenton Hill Hot Dry Rock Geothermal Site with distilled water at 300/sup 0/C and 345 bars total pressure for 8 months has produced many morphological and chemical effects. Eight polished rock disks were mounted on a tantalum pedestal inside a 500-ml autoclave. The autoclave is part of a circulation system designed for operation to 400/sup 0/C and 345 bars. Solution samples were taken at 32, 56, 176, 368, 752, 1544, 3104, and 5816 h. Rock disks were removed also at the latter four times. The reactivity of phases was shown to be quartz>>microcline>plagioclase>mafics, opaques, and trace phases. Quartz was removed congruently. The albite component of the plagioclase was dissolved essentially congruently changing plagioclase from oligoclase (fresh) to bytownite (8 mo.). Microcline showed congruent dissolution. Other phases were inert. Secondary mineralization included phillipsite, thomsonite, and vermiculite.
Date: July 1, 1978
Creator: Charles, R.W.
Partner: UNT Libraries Government Documents Department

Experimental alteration of a granodiorite in a circulation system

Description: Reaction of granodiorite from the Fenton Hill Hot Dry Rock Geothermal Site with distilled water at 300/sup 0/C and 345 bars total pressure for 8 months has produced many morphological and chemical effects. Eight polished rock disks were mounted on a tantalum pedestal inside a 500 ml autoclave. The autoclave is part of a circulation system designed for operation to 400/sup 0/C and 345 bars. Solution samples were taken at 32, 56, 176, 368, 752, 1544, 3104, and 5816 hr. Rock disks were removed also at the latter four times. The reactivity of phases was found to be quartz/microcline/plagioclase/mafics, opaques and trace phases. Quartz was removed congruently. The albite component of the plagioclase was dissolved essentially congruently changing plagioclase from oligoclase (fresh) to bytownite (8 mo.). Microcline showed congruent dissolution. Other phases were inert. Secondary mineralization included phillipsite, thomosonite, and vermiculite.
Date: January 1, 1978
Creator: Charles, R.W.
Partner: UNT Libraries Government Documents Department

Rock alteration in an experimentally imposed temperature gradient

Description: Rock alteration in a dynamic (circulating) hydrothermal system can be applied to any geologic system with mobile fluids. Some examples are geothermal energy extraction, ore mineral extraction, and radioactive waste isolation. While isothermal systems yield important results, polythermal (i.e., temperature gradient) systems more closely model reactions of fluid moving through a rock reservoir. The above examples will generally involve temperature gradients across the rock reservoir. A controlled temperature gradient circulation system was developed to help define these rock-fluid reactions. Six fine grained prisms are placed along the axis of a 113 cm pressure vessel. The prisms are at 72, 119, 161, 209, 270, and 310{degrees}C under flow conditions of 4 cc/min. at 1/3 kbar total pressure. In this experiment a granodiorite was reacted with initially distilled water.
Date: January 1, 1980
Creator: Charles, R.W.
Partner: UNT Libraries Government Documents Department

Higher Education in Texas: Its Beginnings to 1970

Description: Higher Education in Texas is the first book to tell the history, defining events, and critical participants in the development of higher education in Texas from approximately 1838 to 1970. Charles Matthews, Chancellor Emeritus of the Texas State University System, begins the story with the land grant policies of the Spanish, Mexicans, Republic of Texas, and the State of Texas that led to the growth of Texas. Religious organizations supplied the first of many colleges, years before the Texas Legislature began to fund and support public colleges and universities. Matthews devotes a chapter to the junior/community colleges and their impact on providing a low-cost education alternative for local students. These community colleges also played a major role in economic development in their communities. Further chapters explore the access and equity in educating women, African Americans, and Hispanics.
Access: This item is restricted to UNT Community Members. Login required if off-campus.
Date: February 2018
Creator: Matthews, Charles R.
Partner: UNT Press

Deep Borehole Measurements for Characterizing the Magma/Hydrothermal System at Long Valley Caldera, CA

Description: The Magma Energy Program of the Geothermal Technology Division is scheduled to begin drilling a deep (6 km) exploration well in Long Valley Caldera, California in 1989. The drilling site is near the center of the caldera which is associated with numerous shallow (5-7 km) geophysical anomalies. This deep well will present an unparalleled opportunity to test and validate geophysical techniques for locating magma as well as a test of the theory that magma is still present at drillable depths within the central portion of the caldera. If, indeed, drilling indicates magma, the geothermal community will then be afforded the unique possibility of examining the coupling between magmatic and hydrothermal regimes in a major volcanic system. Goals of planned seismic experiments that involve the well include the investigation of local crustal structure down to depths of 10 km as well as the determination of mechanisms for local seismicity and deformation. Borehole electrical and electromagnetic surveys will increase the volume and depth of rock investigated by the well through consideration of the conductive structure of the hydrothermal and underlying regimes. Currently active processes involving magma injection will be studied through observation of changes in pore pressure and strain. Measurements of in situ stress from recovered cores and hydraulic fracture tests will be used in conjunction with uplift data to determine those models for magmatic injection and inflation that are most applicable. Finally, studies of the thermal regime will be directed toward elucidating the coupling between the magmatic source region and the more shallow hydrothermal system in the caldera fill. To achieve this will require careful logging of borehole fluid temperature and chemistry. In addition, studies of rock/fluid interactions through core and fluid samples will allow physical characterization of the transition zone between hydrothermal and magmatic regimes.
Date: March 21, 1989
Creator: Carrrigan, Charles R.
Partner: UNT Libraries Government Documents Department

Technique for Estimating Depth of Floods in Tennessee

Description: From introduction: The purpose of this report is to present methods for estimating depths of various recurrence interval floods for unregulated streams in Tennessee. Relations between the size of the drainage basin and flood depths for four hydrologic areas of the state are defined.
Date: 1983
Creator: Gamble, Charles R.
Partner: UNT Libraries Government Documents Department

Final Report: Nanomaterials in Secondary Battery Research and Development, July 1, 1995 - September 14, 1999

Description: We have been exploring the rate capabilities of nanostructured Li-ion battery electrodes. These nanostructured electrodes are prepared via the template method - a general procedure used to prepare nanomaterials pioneered in the P.I.'s laboratory. The nanostructured electrodes consist of nanofibers or tubules of the electrode material that protrude from a current-collector surface like the bristles of a brush. These nanostructured electrodes show dramatically improved rate capabilities relative to conventional electrode designs.
Date: January 31, 2000
Creator: Martin, Charles R.
Partner: UNT Libraries Government Documents Department

Experimental Investigation of Effects of Combustion-chamber Length and Inlet Total Temperature, Total Pressure, and Velocity on Afterburner Performance

Description: Report presenting an investigation of the effects of afterburner-inlet total temperature, total pressure, velocity, fuel-air ratio, and afterburner combustion-chamber length on afterburner performance and stability limits using a cylindrical afterburner installed in a duct test rig. The afterburner was investigated over a range of total temperature, total pressure, velocity, and afterburner fuel-air ratios.
Date: June 3, 1957
Creator: King, Charles R.
Partner: UNT Libraries Government Documents Department

Sentinel Gap basalt reacted in a temperature gradient

Description: Six basalt prisms were reacted in a controlled temperature gradient hydrothermal circulation system for two months. The prisms were centered at 72, 119, 161, 209, 270, and 310/sup 0/C. Total pressure was 1/3 kbar. All prisms showed large weight loss: 5.5% to 14.9%. The matrix micropegmatite and natural nontronitic alteration reacted readily to clays at all temperatures. The first four prisms were coated with a calcium smectite, and the last two prisms were covered with discrete patches of potassium-rich phengite and alkali feldspar. The results indicated that clays may act as adsorbers of various ions.
Date: January 1, 1983
Creator: Charles, R.W. & Bayhurst, G.K.
Partner: UNT Libraries Government Documents Department

Sentinel gap basalt reacted in a temperature gradient

Description: Six Basalt prisms were reacted in a controlled temperature gradient hydrothermal circulation system for two months. The prisms are centered at 72, 119, 161, 209, 270, and 310/sup 0/C. Total pressure is 1/3 kbar. All prisms show large weight loss: 5.5% to 14.9%. The matrix micropegmatite and natural nontronitic alteration readily react to clays at all temperatures. The first four prisms are coated with a Ca-smectite while the last two prisms are covered with discrete patches of K rich phengite and alkali feldspar. The clays may act as adsorbers of various ions.
Date: January 1, 1982
Creator: Charles, R.W. & Bayhurst, G.K.
Partner: UNT Libraries Government Documents Department

9519 biotite granodiorite reacted in a temperature gradient

Description: A biotite granodiorite from the Fenton Hill Hot Dry Rock (HDR) geothermal system was reacted in a controlled temperature gradient with initially distilled water for 60d. Polished rock prisms were located in the gradient at 72, 119, 161, 209, 270, and 310/sup 0/C. Scanning electron microscope and microprobe analyses show the appearance of secondary phases: Ca-montmorillonite at 72/sup 0/C and 119/sup 0/C; zeolite, either stilbite or heulandite, at 161/sup 0/C; and another zeolite, thomsonite, at higher temperatures. Solution analyses show a steady state equilibrium exists between solution and overgrowths after about 2 weeks of reaction. The chemographic relations for the system are explored in some detail indicating the divariant assemblages may be placed in a reasonable sequence in intensive variable space. These relations predict high and low temperature effects not directly observed experimentally as well as relevant univariant equilibria. Solution chemistry indicates the Na-Ca-K geothermometer more adequately predicts temperature in this system than does the silica geothermometer.
Date: October 1, 1980
Creator: Charles, R.W. & Bayhurst, G.K.
Partner: UNT Libraries Government Documents Department

Environmental geochemistry of radioactive contamination.

Description: This report attempts to describe the geochemical foundations of the behavior of radionuclides in the environment. The information is obtained and applied in three interacting spheres of inquiry and analysis: (1) experimental studies and theoretical calculations, (2) field studies of contaminated and natural analog sites and (3) model predictions of radionuclide behavior in remediation and waste disposal. Analyses of the risks from radioactive contamination require estimation of the rates of release and dispersion of the radionuclides through potential exposure pathways. These processes are controlled by solubility, speciation, sorption, and colloidal transport, which are strong functions of the compositions of the groundwater and geomedia as well as the atomic structure of the radionuclides. The chemistry of the fission products is relatively simple compared to the actinides. Because of their relatively short half-lives, fission products account for a large fraction of the radioactivity in nuclear waste for the first several hundred years but do not represent a long-term hazard in the environment. The chemistry of the longer-lived actinides is complex; however, some trends in their behavior can be described. Actinide elements of a given oxidation state have either similar or systematically varying chemical properties due to similarities in ionic size, coordination number, valence, and electron structure. In dilute aqueous systems at neutral to basic pH, the dominant actinide species are hydroxy- and carbonato-complexes, and the solubility-limiting solid phases are commonly oxides, hydroxides or carbonates. In general, actinide sorption will decrease in the presence of ligands that complex with the radionuclide; sorption of the (IV) species of actinides (Np, Pu, U) is generally greater than of the (V) species. The geochemistry of key radionuclides in three different environments is described in this report. These include: (1) low ionic strength reducing waters from crystalline rocks at nuclear waste research sites in Sweden; (2) oxic ...
Date: September 1, 2003
Creator: Bryan, Charles R. & Siegel, Malcolm Dean
Partner: UNT Libraries Government Documents Department

Phase-Space Reconstruction: a Path Towards the Next Generation of Nonlinear Differential Equation Based Models and Its Implications Towards Non-Uniform Sampling Theory

Description: This paper explores the overlaps between the Control community’s work on System Identification (SysID) and the Physics, Mathematics, Chaos, and Complexity communities’ work on phase-space reconstruction via time-delay embedding. There are numerous overlaps between the goals of each community. Nevertheless, the Controls community can gain new insight as well as some new very powerful tools for SysID from the latest developments within the Physics, Mathematics, Chaos, and Complexity communities. These insights are gained via the work on phase-space reconstruction of non-linear dynamics. New methods for discovering non-linear differential based equations that evolved from embedding operations can shed new light on hybrid-systems theory, Nyquest-Shannon’s Theories, and network based control theory. This paper strives to guide the Controls community towards a closer inspection of the tools and additional insights being developed within the Physics, Mathematics, Chaos, and Complexity communities for discovery of system dynamics, the first step in control system development. The paper introduces the concepts of phase-space reconstruction via time-delay embedding (made famous byWhitney, Takens, and Sauer’s Thoreoms), intergrate-and-fire embedding, and non-linear differential equation discovery based on Perona’s method.
Date: August 1, 2009
Creator: Tolle, Charles R. & Pengitore, Mark
Partner: UNT Libraries Government Documents Department

Status of Modeling Efforts for the Wairakei Geothermal Field

Description: The theoretical model used in this study is based on an approach that combines the mass, momentum and energy balances for steam and water into two partial differential equations in terms of the dependent variables, pressure and enthalpy. The assumptions used in this formulation and the detailed development of the equations are presented in Faust (1976). The resulting two- and three-dimensional equations are approximated by finite-difference expressions, and are solved using either direct or iterative matrix techniques. Our conceptual model of the Wairakei system is basically the same as that outlined in Mercer, Pinder and Donaldson (1975), with the exception that we now allow for mass leakage through the bottom of the reservoir. The Wairakei hydrothermal system is considered to have been at steady state prior to exploitation. The first step in modeling the Wairakei field is therefore the reproduction of the observed virgin or steady state conditions. The results of the steady state simulation are used as initial conditions for the transient model of exploitation. This modeling effort represents an ongoing project, and the results to be presented will describe the current status of our Wairakei simulation. 4 refs.
Date: December 1, 1976
Creator: Mercer, James W. & Faust, Charles R.
Partner: UNT Libraries Government Documents Department

Integrated structural health monitoring.

Description: Structural health monitoring is the implementation of a damage detection strategy for aerospace, civil and mechanical engineering infrastructure. Typical damage experienced by this infrastructure might be the development of fatigue cracks, degradation of structural connections, or bearing wear in rotating machinery. The goal of the research effort reported herein is to develop a robust and cost-effective structural health monitoring solution by integrating and extending technologies from various engineering and information technology disciplines. It is the authors opinion that all structural health monitoring systems must be application specific. Therefore, a specific application, monitoring welded moment resisting steel frame connections in structures subjected to seismic excitation, is described along with the motivation for choosing this application. The structural health monitoring solution for this application will integrate structural dynamics, wireless data acquisition, local actuation, micro-electromechanical systems (MEMS) technology, and statistical pattern recognition algorithms. The proposed system is based on an assessment of the deficiencies associated with many current structural health monitoring technologies including past efforts by the authors. This paper provides an example of the integrated approach to structural health monitoring being undertaken at Los Alamos National Laboratory and summarizes progress to date on various aspects of the technology development.
Date: January 1, 2001
Creator: Farrar, C. R. (Charles R.)
Partner: UNT Libraries Government Documents Department

Optimal Timing of Geothermal Energy Extraction

Description: This paper is concerned with the optimal time to commence extraction of energy from a hot-water geothermal reservoir. The economic models that we have presented in the past have the common characteristics that the extraction program starts immediately (see References 1 and 2). Based on this assumption, we determined optimal extraction strategies and planning horizons such that the present values of total profits were maximized. In this study we relax the requirement that extraction be undertaken immediately, seeking instead the delay in starting time that along with the other decision variables maximizes the present value of total profits over the economic life of the reservoir. Of course, optimal starting time, economic life of the reservoir, optimal extraction rate, and optimal injection temperature are interrelated, and therefore, we analyze their effect on the overall planning strategy simultaneously. 4 refs.
Date: December 14, 1977
Creator: Golabi, Kamal & Scherer, Charles R.
Partner: UNT Libraries Government Documents Department

Defining a Possible Low LET Bystander Effect

Description: Current radiation protection guidelines assume a linear response to ionizing radiations down through doses where epidemiological studies provide very limited to no information as to the propriety of such assumptions. The bystander response is a non-targeted effect which might impact such guidelines. These studies while clearly affirming a bystander response for high LET radiations, do not provide such affirmation for environmentally relevant low dose, low LET radiations. Caution and further study are necessary before making judgements that could impact on current standards.
Date: May 4, 2009
Creator: Geard, Charles R.
Partner: UNT Libraries Government Documents Department

Optimal Management of a Geothermal Reservoir

Description: In a presentation to the First Stanford Geothermal Workshop last year, we outlined the basic philosophy, assumptions and general approach to finding an optimal rate of energy extraction from a hot water geothermal field. In this paper, we present the explicit relationships governing the physical processes and economic factors of our model, as well as the modifications to the model that have been necessary to accommodate the more specific articulation of these relationships. The conceptual modifications of the earlier model are subtle, but of great importance in making our work more useful for geothermal resource management. We adopt the hydro-thermal model developed by Gringarten and Sauty, and assume that the value of geothermal energy is known as a function of time and the quantity of extracted energy. We note however that our optimization model can be modified to accommodate other hydrothermal models such as that of Kasameyer and Schroeder, which combines fractured and porous media flow. In view of the increase in the attractiveness of geothermal energy for space heating, we also assume that the extracted energy is used for generation of steam to be used for this purpose. However, we are well aware that the hot brine, depending on the parameters of a particular field, may be more economically utilized for some other purpose (e.g., electric power generation, direct utilization of hot water for domestic and industrial use, mineral extraction and desalinization). In this paper, we restrict our attention to the case where the decision has already been made to use the geothermal energy for space heating. Further proposed work is described at the end of the paper. 2 figs., 6 refs.
Date: December 1, 1976
Creator: Golabi, Kamal & Scherer, Charles R.
Partner: UNT Libraries Government Documents Department

Progress Report on Multiphase Geothermal Modeling

Description: Work over the past year has concentrated on three areas: 1) to implement a concept of vertical equilibrium in geothermal modeling, 2) to improve the matrix equation solution technique for both two- and three-dimensional models, which improvements this report describes in detail, and 3) to apply a vertical equilibrium, areal model to the Wairakei, New Zealand geothermal field. The steady-state modeling indicates that large regions in the reservoir probably had a small steam cap prior to exploitation. Furthermore, transient simulations indicate that leakage into the reservoir is significant; that is, the Wairakei reservoir is not a closed system. The most difficult part of history matching at Wairakei is adjusting permeabilities in order to remove enough mass from storage (as opposed to leakage) and reproduce the observed pressure decline trends. 5 refs.
Date: December 14, 1977
Creator: Mercer, James W. & Faust, Charles R.
Partner: UNT Libraries Government Documents Department